u An 3) a -0 <■ a> (D o c c 3 o (Q » O z 3- 00 a> S ■* ^• m z O 3- OD O y o 3 (A O Z 5 .^ to' ■D o en ^ 3 0) CT O o I C H S ^. m 5' ■< o o 0> 3 H o w O rv) (C z -3 o H ^ > rv) a o o (/> 3 m z o -< §■ n z < O O z en ^ S ? 5 =0 -n O S O z > o m Z o -< TE( ))iirt«- imrmR^ water pollution control research series • I3030ELY 6/71 -io »"''(fl||l>^ REC-R2-7I-IO DWR NO. 174—13 BIO- ENGINEERING ASPECTS OF AGRICULTURAL DRAINAGE JUN 5 1976 SAN JOAQUIN VALLEY, CALIFORNIA n TECHNIQUES TO REDUCE NITROGEN IN DRAINAGE EFFLUENT DURING TRANSPORT I IRONMENTAL PROTECTION AGENCY#RESEARCH AND MONITORING Lfe iJMiTPn ciTATP-c; m iRP-Ai I r^p- op-r^i AK>tA-rir^tvi u BIO -ENGINEERING ASPECTS OF AGRICULTURAL DRAINAGE SAN JOAQUIN VALLEY, CALIFORNIA The Blo-Engineerlng Aspects of Agricultural Drainage reports describe the results of a unique interagency study of the occurrence of nitrogen and nitrogen removal treatment of subsurface agricultural wastewaters of the San Joaquin Valley, California, The three principal agencies involved in the study are the Water Quality Office of the Environmental Protection Agency, the U. S. Bureau of Reclamation, and the California Department of Water Resources. Inquiries pertaining to the Bio -Engineering Aspects of Agricultural Drainage reports should be directed to the author agency, but may be directed to any one of the three principal agencies. THE REPORTS It is planned that a series of 12 reports will be issued describing the results of the interagency study. There will be a summary report covering all phases of the study. A group of four reports will be prepared on the phase of the study related to predictions of subsurface agricultural wastewater quality — one report by each of the three agencies, and a summary of the three reports. Another group of five reports has been prepared on the treatment methods studied and on the biostimulatory testing of the treatment plant effluent. There are four basic reports and a summary of the reports. This report, "REMOVAL OF NITROGEN FROM TILE DRAINAGE", is the summary report . The other three planned reports will cover (l) techniques to reduce nitrogen during transport or storage, (2) possibilities for reducing nitrogen on the farm, and (3) desalination of subsurface agricultixral wastewaters . BIO-ENGINEERING ASPECTS OF AGRICULTURAL DRAINAGE SAN JOAQUIN VALLEY, CALIFORNIA TECHNIQUES TO REDUCE NITROGEN IN DRAINAGE EFFLUENT DURING TRANSPORT Prepared by the United States Bureau of Reclaination Region 2 The agricultural drainage study was conducted under the direction of: Robert J. Pafford, Jr., Regional Director, Region 2 UNITED STATES BUREAU OF RECLAMATION 2800 Cottage Way, Sacramento, California 95825 Paul DePalco, Jr., Regional Director, Pacific Southwest Region WATER QUALITY OFFICE, ENVIRONMENTAL PROTECTION AGENCY 760 Market Street, San Francisco, California 94102 John R. Teerink, Deputy Director CALIFORNIA DEPARTMENT OF WATER RESOURCES 1416 Ninth Street, Sacramento, California 95814 June 1971 For sale by the Superintendent of Documents, U.S. QoTernment Printing Office, Washington, D.C. 20402 - Price 60 cents REVIEW NOTICE This report has been reviewed by the Water Quality Office, Environ- mental Protection Agency and the California Department of Water Resources, and has been approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the Water Quality Office, Environmental Protection Agency, or the California Department of Water Resources. The mention of trade names or commercial products does not constitute endorsement or recom- mendation for use by either of the two federal agencies or the Cali- fornia Department of Water Resources. 11 ABSTRACT Three methods to remove nitrates from the agricultural drainage water from the San Luis Service Area were investigated. One method was a theoretical evaluation of nitrate removal by algae during the transport of the drainage water in the San Luis Canal or during storage in the Kesterson Reservoir. The other methods were designed to promote anaerobic bacterial denitrif ication in a continuous flow of drainage water. One method used barley straw and the other water grass grown in shallow ponds as the carbon energy source. The barley straw was placed in a trench about 10 feet deep and the nitrate removal rate determined under various flow and detention rates. The water grass was grown in ponds under a continuous flow of water of about 4 to 6 inches depth. Under optimum conditions both methods reduced the nitrate -N con- centration of the drainage water from a maximum of about 30 mg/1 to less than 2 mg/1. The cost of nitrogen removal by the shallow grass plot systems, the most economical and feasible of these methods, was estimated to be $6.50 per acre foot or $20.00 per million gallons. BACKGROUND This report is one of a series which presents the findings of in- tensive interagency investigations of practical means to control the nitrate concentration in subsurface agricultural wastewater prior to its discharge into other water. The primary participants in the program are the Water Quality Office of the Environmental Protection Agency, the United States Bureau of Reclamation, and the California Department of Water Resources, but several other agencies also are cooperating in the program. These three agencies initiated the program because they are responsible for providing a system for disposing of subsurface agricultural wastewater from the San Joaquin Valley of California and protecting water quality in California 'a water bodies. Other agencies cooperated in the program by provid- ing particular knowledge pertaining to specific parts of the overall task. The ultimate need to provide subsurface drainage for large areas of agricultural land in the western and southern San Joaquin Valley has been recognized for some time. In 19 54, the Bureau of Reclamation included a drain in its feasibility report of the San Luis Unit. In 19 57, the California Department of Water Resources initiated an investigation to assess the extent of salinity and high ground water problems and to develop plans for drainage and export facili- ties. The Burns-Porter Act, in 1960, authorized San Joaquin Valley drainage facilities as part of the State Water Facilities. The authorizing legislation for the San Luis Unit of the Bureau of Reclamation's Central Valley Project, Public Law 86-488, passed in June 1950, included drainage facilities to serve project lands. This Act required that the Secretary of Interior either provide for constructing the San Luis Drain to the Delta or receive satisfactory assurance that the State of California would provide a master drain for the San Joaquin Valley that would adequately serve the San Luis Unit. Investigations by the Bureau of Reclamation and the Department of Water Resources revealed that serious drainage problems already exist and that areas requiring subsurface drainage would probably exceed 1,000,000 acres by the year 2020. Disposal of the drainage into the Sacramento-San Joaquin Delta near Antioch, California, was found to be the least costly alternative plan. Preliminary data indicated the drainage water would be relatively high in nitrogen. The then Federal Water Quality Administration conducted a study to determine the effect of discharging such drainage water on the quality of water in the San Francisco Bay and Delta. Upon completion of this study in 1967, the Administration's report concluded that the nitrogen content of untreated drainage waters could have significant adverse effects upon the fish and recreation values of the receiving waters. The report recommended a three-year research program to establish the economical feasibil- ity of nitrate-nitrogen removal. As a consequence, the three agencies formed the Interagency Agricultural Wastewater Study Group and developed a three-year cooperative research program which assigned specific areas of responsibility to each of the agencies. The scope of the investi- gation included an inventory of nitrogen conditions in the potential drainage areas, possible control of nitrates at the source, predic- tion of drainage quality, changes in nitrogen in transit, and methods of nitrogen removal from drain waters including biological- chemical processes and desalination. CONTENTS Section Page I Conclusions 1 II Recommendations 3 III Introduction 5 IV Objectives 7 V Methods, Materials and Results 9 Nutrient Removal by Algae Growth Within the Transport System 9 Utilizing San Luis Canal 9 Utilizing Kesterson Reservoir 10 Nutrient Removal by Field Denitrif ication Processes 11 Sample Collection and Analytical Techniques 13, Deep Trench Study 13 Methods and Materials 14 Results 14 Detention Time 20 Temperature 20 Energy Source Requirements 20 Electrical Conductivity 21 Grass Plot Study 22 Methods and Materials 22 Results 23 Dissolved Oxygen 27 Temperature 29 Percolating Water Studies 29 VI Cost Analyses 35 VII Discussion 41 VIII Acknowledgements 45 IX References 47 FIGURES Number Page 1 Plans of Denitrification Plots 12 2 Deep Trench - Nitrate Concentrations and Temperatures 15 3 Deep Trench - Dissolved Oxygen 16 4 Grass Plot - Nitrate Concentration - October 1968 - September 1969 24 5 Grass Plot - Nitrate Concentration - October 1969 - April 1970 25 6 Deep Trench Nitrate Reduction Ponds 39 7 Shallow Nitrate Reduction Ponds 40 TABLES Number Page 1 Chemical Analysis of Supply Water 13 2 Nitrate Concentration, Dissolved Oxygen and Detention Time of Water in Deep Pond Studies 15 3 The Concentration of the Various Nitrogen Forms, pH, Electrical Conductivity and Temperature of the Supply and Discharge Water at Various Times During the Deep Trench Experiment 20 4 Flow Rates, Detention Times and Straw Requirements of Deep Pond 22 5 Calculated Inflow Rates and Theoretical Detention Times of the Various Checks in the Grass Plot 26 6 Algae Count at Several Sampling Sites in Grass Plots - February 26, 1970 27 7 Concentration of Various Nitrogen Forms, Temperature, pH and Electrical Conductivity at Four Locations in the Plot 28 8 The Nitrate -N Con(':entration of the Soil Extract from Several Depths Below the Grass Plot 30 9 Quantity of Surface Flow, NO3-N Concentration and Deep Percolation in the Grass Plot for an Average 24-hour Period 31 10 Estimated Cost for Removal of Nitrogen by Deep Pond Method 37 11 Estimated Costs for Removal of Nitrogen by Shallow Grass Plot Method 38 IX SECTION I CONCLUSIONS 1 - The two methods, deep trench and the shallow grass ponds, investigated at the San Luis Wasteway are technically feasible and capable of removing nitrates to varying degrees. 2 - The shallow grass pond method, except for a one - or - two month period in the late fall or early winter, was more efficient than the deep trench methods. 3 - The shallow grass pond method offers the potential for costs which are substantially lower than other nitrogen removal treatment processes studied by the Interagency Group, if it can be demonstrated that sustained operations, under field conditions, will yield the desired qualities of effluent. 4 - The cost of treating the projected tile drainage effluent from the San Luis area by the shallow grass pond method, based on information developed in this study, would be approximately $20 per million gallons or $6.50 per acre foot. 5 - Further investigations are required before a full-scale operation of this method should be employed. SECTION II RECOMMENDATIONS The investigations to date indicate that the shallow pond method has a potential for nitrate removal at a reasonable cost therefore it is recommended that further studies be conducted on this method and variations of this method to gain additional data on optimum operating conditions and design criteria. When the San Luis Drain and the Kesterson Reservoir go into operation it is further recomjnended that a full scale plot be set up in the Reservoir. SECTION III INTRODUCTION The San Luis Canal-California Aqueduct, a joint Federal and State of California water operation, will import large quantities of water into the westside of the central and southern San Joaquin Valley. This importation of water will permit more intensive surface irrigation of the lands and will reduce the amount of pumping from the groundwater. These factors combined with the relatively slowly permeable and stratified soils will promote the formation of saline, high ground-water in much of the area. A system of on-farm subsurface drains will be required to maintain the groundwater at an acceptable level if land productivity is to be maintained. To provide an outlet for the farm drain effluent from the San Luis Service Area the United States Bureau of Reclamation has started construction of the San Luis Drain. During the first stage of operation this Drain will terminate at the Kesterson Reservoir. Ultimately the Drain is designed to discharge into the Sacramento- San Joaquin Delta near Antioch. When conditions warrant, the State of California plans to construct a drainage canal to serve the remainder of the Valley which is also planned to discharge into the Delta. The water collected from these subsurface drains and carried by the drainage canals is expected to contain relatively high concentrations of nitrate-nitrogen. Recent studies (1,2) suggest levels of approximately 20 milligrains per liter (NO3-N) and this may have a potential for causing undesirable algae blooms in the receiving water of the Delta. SECTION IV OBJECTIVES An objective of the project was to determine changes in N-forms during transit to treatment systems. One of the original plans was to evaluate the change in N in drainage waters as they moved through an operating canal system. A search was made in areas which have climatological, soil and irrigation conditions somewhat similar to those in the San Joaquin Valley. A check of the nitrogen concentration in the drainage systems in the Wellton-Mohawk, Gila and Imperial Valley service areas, did not reveal any systems which had quantities of nitrogen sufficiently high to give any significant evaluation. To satisfactorily duplicate the anticipated nitrate levels of the San Luis Drain water would involve prohibitive costs for addition of nitrates to a system of similar size. The reduction to experi- mental scale would result in smaller costs for nitrate addition; however, the biological environment might then be poorly duplicated and the results would be of questionable value. Consequently measurements of this type, were postponed until sections of the San Luis Drain are completed. At that time, any changes in nitrogen in the drainage water from the San Luis service area during trans- port from Westlands Water District to the Kesterson Reservoir can be monitored. Therefore, in lieu of the study of changes in transport, the emphasis of this project was shifted to determine what changes could be effected in the drainage waters by using facilities similar to the designed transport and storage system facilities and the use of agricultural waste products. Tv;o separate studies were made to accomplish these objectives. One was a plan to combine nutrient removal by promoting algae growth within the transport system, the San Luis Drain and the Kesterson Reservoir. This method of treatment was proposed by a team from the Firebaugh Waste Water Treatment Center (3). The evaluation of this proposal was based primarily on theoretical calculations rather than on an experimental model. The second study was concerned with nitrate removal in the transportation system by the denitrifi- cation process. This later study was in two phases, one utilized an elongated, relatively deep pond somewhat similar to a section of the San Luis Drain and the other a broad relatively shallow pond, similar to a cell of Kesterson Reservoir. SECTION V METHODS, MATERIALS AND RESULTS This section describes the method and materials used in the study of techniques to reduce nitrogen concentrations in drainage effluent during transport or storage and discusses the result of the findings of the investigations. Nutrient Removal by Algal Growth within the Transport System A study was prepared by Joel C. Goldman, James F. Arthur and others (3) on the possibility of using the San Luis Drainage transport and storage systems as a means to remove nutrients by the growth and harvesting of algae in these facilities. The plan was proposed on the premise that, under favorable environmental conditions, there will be a natural growth of algae within the San Luis Drain and Kesterson Reservoir, and that if, maximum algal growth was promoted it could serve as a dual treatment - transport system. The study was based primarily on basic assumptions and theoretical calculations rather than on an experimental model. Some of the criteria, particularly the projected flow of the San Luis Drain and the size of Kesterson Reservoir have been changed since the report was published, however, the basic theories, cal- culations and conclusions in the study remain valid. Calculations in the study indicated that the biomass required to remove 90 percent of the estimated 25 mg/1 of nitrogen in the drainage water would be 280 mg/1. It was postulated that a portion of this quantity that could be grown in the Drain or the Reservoir would reduce the land requirements for nutrient removal in the treatment facilities thereby reducing the total nitrogen removal costs. The study suggested that any action which could reduce the acreage requirements in the Antioch area where land values are high would be especially effective in reducing the overall project costs. Utilizing the San Luis Drain The studies indicated that the actual algal concentrations that will be in the Drain are almost impossible to predict. When flow in the San Luis Drain reaches its projected capacity it will have a surface area of about 770 acres and a mean detention time of 6.3 days. Algal cells will multiply rapidly, doubling about ij to 1 times per day, thus there would probably be 4 or 5 doublings during transit. Based on Dr. William Oswald's calculations and his most conservative estimate of an original concentration of 1 mg/1 of algae and 4 doublings during transit to the Delta, then 15 mg/1 of algae would be present at discharge. His less conservative estimate assumed that the water started with 2 mg/1 of algae and there were 5 dou- blings, then the final concentration would be 64 mg/1. Theoretically, based upon Dr. Oswald's calculations, the Drain has the capability of supporting about 100 mg/1 of algae considering light limitations only. Shallow ponding would be required to attain any further increment of growth. An approximation of the amount of nitrogen removed from the drain- age water through the growth of the algae can be calculated by making several assumptions: 1. Final algal concentration - 16 to 64 mg/1. 2. Nitrogen content of algal cells » 8-10 percent (use 8 percent) 3. Total nitrogen concentration in drainage water - 20-25 mg/1 (use 25 mg/1) Thus the amount of nitrogen removed from drainage water and con- verted into algal cell material can be calculated as follows: 16 mg/1 X 0.08 » 1.28 mg/1 (minimum estimate) 54 mg/1 X 0.08 - 5.12 mg/1 (maximum estimate) or approximately: 1.28 X 100 - 5 percent (minimum estimate) 25 5.12 X 100 « 20 percent (maximum estimate) 25 of the incoming nitrogen will be removed. Since the amount of nitrogen removed will be directly proportional to the concentration level of algae, nitrogen removal could be increased by increased algal growth in the Drain. Methods to gain increased growth would be to seed the Drain to get as high an initial algal concentration as practical and then encourage as many doublings as possible to occur during transit. Doublings could be increased by modifying the Drain to create greater turbulence and effective surface area by placing baffles in the Drain, aerating or adding gases. Utilizing Kesterson Reservoir The study points out that the Kesterson Reservoir, an integral part of the Drain system, could be utilized as a combined reservoir and algae growth treatment plant. If the algae growth system was designed for the optimum operating depth and a storage capacity depth of two feet, the system would have the capability for essentially 100 percent treatment and still serve as an emergency storage reservoir. 10 This system could be designed to minimize the power required for mixing by taking advantage of the natural land slope to the north. The design would entail a series of equally spaced channels running along the length of the reservoir in the direction of the slope. If it was necessary, pumps could be used to produce the required initial mixing velocities. Any desired detention time could be maintained by recirculating a portion of the effluent. Research at Firebaugh indicates that both the "bacterial denitrifi- cation" and the algae "growth and harvest" are technically feasible, therefore, a combination of the two systems in a series type opera- tion might give the best results. The algae growth and harvest could take place in the Drain and Kesterson Reservoir followed by anaerobic filters for final treatment. Nutrient Removal by Field Denitrif ication Processes The denitrif ication studies were based upon the principle that in the presence of an adequate concentration of a degradable organic material and restricted aeration bacteria will utilize the available dissolved oxygen. Then, in the absence or near absence of oxygen, denitrif ication is accomplished by facultative anaerobic bacteria which are capable of using NO? in place of oxygen as a hydrogen acceptor. The reactions which take place in this reduction process are subject to a certain amount of controversy and speculation. Nightingale (4) suggests a basic simplified multi-step reaction pathway as follows: ^ 0- ,0 N-OH N ^ N N - + 2H-^N + 2H2O 6H II + 2H2O— "I ^ O+H2O 2H ill + H2O "* '"O ^ N-OH N " " N Nitrate Nitrite Hyponitrite Nitrous Oxide Nitrogen Gas The denitrif ication studies were carried out in two phases. One, at the Firebaugh Center, had the main responsibility for anaerobic denitrif ication with methanol. The other, conducted near the San Luis Wasteway, main interest was denitrif ication with natural carbon sources. In the latter projects, barley straw was used as the carbon energy source in the deep trench study and water grass grown in place was the source in the shallow pond study. The plots were set up on Bureau of Reclamation owned land near the San Luis Wasteway approximately 5 miles northwest of Los Bancs. The soils in the area are classified as Orestimba clay loam (5). These soils are developed on alluvial material derived from the softly consolidated calcareous, gypsiferous sandstones and shales of the Coast Range Mountains. They are moderately to strongly saline with slight to moderate compaction in the subsoil. Plans of the systems are shown in Figure 1. 11 The water supply for the investigations was pumped from the San Luis Wasteway which contains a mixture of groundwater and imported Delta- Mendota Canal water. The total quantity and the distribution of various ions in the water varied with the season. A representative analysis of the water is listed in Table 1. Table 1 Chemical Analysis of Supply Water pH conductivity Ca Mg Na NO3 CO, HCO3 CI SO4 T.D.S. ECXIO^ mg/1 7.6 1400 37 42 172 4 378 203 48 884 The nitrate concentration of the supply water normally was less than 5 mg/1. Because of this low nitrogen level, for purposes of this study, it was necessary to supplement the water with nitrates. This was accomplished by dissolving calcium nitrate in a large supply tank and then running this through a small balancing tank into the supply ditch. It was planned to maintain a NO3-N level of approx- imately 9 mg/l in the deep trench and 14 mg/1 in the shallow ponds. However, maintaining this desired level proved to be difficult due primarily to clogging of the outflow valve by precipitated salts and foreign matter. Sample Collection and Analytical Techniques Samples were collected from the plots and analyzed by the methods listed below: Analysis Method Nitrates Specific Ion Meter (6) and/or Brucine (7) Total Nitrogen (Kjeldahl) Micro Kjeldahl Ammonia Distillation Organic Nitrogen Micro Kjeldahl Dissolved Oxygen Winkler (Hach) pH Glass Electrode Electrical Conductivity Conductivity Bridge Mineral Constituents Laboratory Procedures (8) In addition to the chemical analysis the temperatures were monitored. The rate of inflow and outflow was measured by a Parshall flume equipped with a continuous stage water recorder. Deep Trench Study This investigation was conducted in a trench designed to simulate a section of the San Luis Canal. 13 Methods and Material A trench approximately 10 feet deep, 20 feet wide at the top and 200 feet long was excavated. The trench was filled with drainage water supplemented with calcium nitrate and covered with a layer of barley straw approximately six inches thick. Additional straw was added periodically as open spots appeared in the straw cover. The barley straw was the degradable organic material used as the energy source for the bacteria. The system was planned to operate as simply as possible with water entering the trench from a supply ditch flowing through the straw covered trench. However soon after the start of the experiment it became obvious that the inflow water was short-circuiting through the trench without completely displacing the water in the trench. Two five mil polyethylene plastic curtains were suspended across the trench 2 5 feet and 50 feet downstream from the inlet to alleviate this problem. These curtains acted as baffles to force the water flow downward. Although there were still stagnant areas in the system, especially near the botton, the baffles did increase the percentage of the water that was displaced. A dissolved oxygen sampler was used to collect samples from the middle of the trench 2 feet below the water surface at the inlet and outlet and at stations 10, 25, 50, 50, 100 and 175 feet down- stream from the inlet. At the 175-foot station, near the outlets of the trench, samples also were collected at depth of 4 and 8 feet. All samples were analyzed for nitrates, dissolved oxygen, pH and electrical conductivity. In addition some of the samples were analyzed for nitrites, ammonia and organic nitrogen. Results - Samples were collected from the trench between October 1967 and July 1958. The nitrate concentrations of the drainage water at sampling points and for various dates as the water moved through the trench are listed in Table 2. The variabil- ity of the nitrate concentration of the supply water at the inlet was due to fluctuations in the flow from the supplemental nitrate supply system. The amount of nitrate removal ranged from almost complete removal of the nitrate to less than 50 percent. Although the removal rate varied widely, the reduction that did occur normally took place within the first 50 foot lengths of the trench. The nitrate concentration of the supply and the discharge waters and the temperature of the discharge water for data collected between October 1957 and July 1958 are shown in Figure 2. Although most of the nitrate reduction took place within the first 50 feet, the detention times listed below were based on the water flowing through the entire reach of the trench. The detention times used in this study were theoretical times based on the volume of the trench divided by the influent flow rates. These calculations neglected possible short-circuiting and stagnant zones in the 14 — ' o V — —> z vOsO -Of^r^rorOCN rn ro ro rn r^ r^ m m (— ir^nOOOOf^'^"^''^''^"^ r^ r-i m rn ^^Olnooaooooocx^aooOQOoooO'/^'/^u^>'^ao5fnr-lrOf2 csi ^ tNiOOOOr^aooOOOoOoooOaOOOOOaOr^r^r-r^McO""'''*''''^ i/^ \r\ ir\rnrofomt— *cnj o o o 3 ^ O O O I o ,J-J— oco>o 3 Q — ' z ■ O O 3 OO^OO^OOOO^O-DOO-OOOO^OOO O o-^ ooOOOO-D^ C u 00 > >. Ill X V5 o ■O CO o -^ O 30 00 00 00 O CM (SICMtMCMfMCMOJOOOO.-vlP^J<^r-ir<4t>>< o oo ooooooojtNj^^-*x>ooor^ooao30r^o^oo»ooooooooaoajaO'^^ r^r^(^O^Or^O00~J— '0'~^:^'^^<7^30a'Au-iiAO Oo- S3aniVd3dW3i o <;;-^|^^ °o > ^~~~~~~~--. ■> « ^ c' y ^ -a; ■ ^^ O CT> 4C « o ~-~~^ -— " ^ -SA aiwog p»l|04l(J| < " -~-:^ > c_ r i f - o - UJ - Q q: 3 Q Z < to z o < (£ »- Z UJ o z o o UJ a: ^ 1/BVM N-3iVailN 16 trench, therefore, the true values are probably less than those listed here. Table 2 lists the detention times and the dissolved oxygen concentrations at the various sampling stations in the trench for several dates during the study. During the first six months of the study the NO,-N concentration of the supply water normally ranged between 5 and 3 mg/1 with an average concentration of about 8 mg/1. During the last three months the NO^-N concentration rate was increased to an average of about 14 mg/1. During the first month of the experiment a detention time of 5.9 days was maintained. At this rate the nitrate nitrogen concentration in the discharge water was reduced to less than 1 mg/1. When the deten- tion was reduced to 3.5 days the NO^-N concentration in the dis- charge water was about 3 mg/1 or about 57 percent of the concentra- tion of the supply water. When a fresh supply of straw was added to the trench the NO3-N in the discharge water was reduced to zero with no change in the 3.5 day detention time. A further decrease of the detention time to 2 days resulted in a rise in the NO-j-N content of the discharge water to about 4 mg/1. The detention time was increased to 3 . 3 days but no appreciable change in the nitrate content of the discharge water was noted. It was concluded that the reason for the lack of response to the change was that the effective detention time was being reduced by the short-circuiting of the water and the disappearance of the more readily available energy source in the straw. The system was redesigned to overcome this problem by installing the two baffles and adding more straw. After the system was changed and with approximately the same deten- tion time, 3.3 days, the NO3-N concentration in the discharge water was reduced to less than 1 mg/1. The conditions were kept constant and this near complete reduction rate was maintained for about a month. When the detention time was again reduced to 2.0 days the nitrate concentration in the discharge water increased. Even though the detention time was later increased to 4.5 days, the nitrate reduction rate remained at about 40 percent. It is postulated that the principle reason for the lower reduction rate during the later part of the study was the lack of an adequate, available organic energy source to maintain the bacterial population required for removal of all the nitrates in the system. Fresh straw was added routinely at the rate of about 300 pounds per week to maintain a solid cover over the water. This quantity apparently did not replenish the organic carbon source as rapidly as it was used. In part this problem was the result of wind blown dust deposited in the straw-water mixture. As this dust became mixed with the other 17 components a soil-water-straw mixture was formed on the surface of the water in the trench which was relatively unusable as an energy source for the bacteria. This material floated on or near, the water surface and prevented much of the fresh straw from coming in contact with the water in the trench. The dissolved oxygen content of the supply water and the discharge water at various dates during the period of the study are plotted in Figure 3. The dissolved oxygen content of the supply water, normally sampled near midday, ranged from 5 to 10 mg/1. The content of the discharge water ranged from zero to 7 mg/1. There was a very close correlation between the dissolved oxygen content reduc- tion and amount of nitrate reduction. During those periods when the nitrate levels were reduced to near zero the dissolved oxygen contents were also near zero. This correlation is to be expected, however, it is somewhat surprising that there was at least partial denitri- fication although the dissolved oxygen apparently was not reduced to zero. It was assumed that this denitrification occurred in some local areas within the system where there was complete or near anaerobic conditions which were not detected in our sampling pro- gram. Although no determinations were made, at times it was evident from the odor of hydrogen sulfide that sulfate reduction was occurring. As the presence of nitrates inhibits sulfate reduction the appear- ance of hydrogen sulfide in the trench would indicate the removal of most or all of the nitrates from the water (9). Several times during the investigation the hydrogen sulfide odor plus those from some of the other decomposition products of the straw caused a rather unpleasant environment around the plot area. A number of nitrite and ammonia analyses were made of the supply and discharge water to determine if there was a build up of either of these nitrogen forms in the water in the trench during the denitri- fication process. Table 3 lists the quantities of NO3-N, NO2-N and NH3-N found in the supply and discharge water at various times during the experiment. Also included are the pH, electrical conductivity and temperature of the water at the time it was sampled. The NO2-N did not increase significantly except during the coldest weather. During this cold period the increase in nitrite accounted for only about 4% of the nitrate reduction. Most data show that there was a reduction in the ammonia. One reason for the relatively high concentration of ammonia in the supply water is that there was a small percentage of this salt mixed with the Ca(N03)2 which was used as the nitrate source to supplement the native nitrogen in the water. There were several factors such as the energy source, detention time and temperature which affected the reduction rate of the nitrates and dissolved oxygen. These factors are inter-related or are masked sufficiently to prevent the analyses made in this study from showing the relative contribution of each. 18 in O cvj rO CM "O in % 1 c c ^ E J L dUPa pai|D*sui .J UJ 00 ID CD > _i o CO CO X UJ cr Q. UJ UJ Q N39AXO QBAIOSSia - l/0\n 19 Table 3 The Concentrations of the Various Nitrogen Forms, pH, Electrical Conductivity and Temperature of the Supply and Discharge Water, at Various Times During the Deep Trench Experiment. N-Form pH NO3-N NO2-N NH3-N EC mmhos Temp. °C 0.3 0.19 7.4 0.55 23 0.1 0.17 6.9 0.69 21 _ 0.57 7.3 0.63 17 - 0.55 7.6 0.65 16 0.4 0.38 7.9 1.70 10 0.7 0.48 7.9 1.60 10 0.05 0.90 7.6 1.90 17 0.00 0.48 7.4 1.90 17 0.08 1.1 7.8 1.45 22 0.29 0.06 8.0 1.50 22 0.1 1.15 8.3 1.30 30 0.4 0.67 8.3 1.20 27 10-21-67 Supply 14.5 " Discharge 11-13-67 Supply 11.2 " Discharge 2.0 1-03-68 Supply 10.0 " Discharge 2.3 3-06-68 Supply 9.6 " Discharge .1 5-01-68 Supply 18.0 " Discharge 3.0 7-10-58 Supply 15.0 " Discharge 6.2 Detention Time - The calculated theoretical detention time of the entire system for this study ranged from 2 to 6 days. Some generalizations can be made about the effect of detention time on nitrate removal from this system. First, when there were no other limiting parameters almost complete reduction of the nitrates was obtained with a detention time of 3.3 days. With detention times of less than 3.3 days, there was never more than 80 percent reduc- tion of the nitrates. Temperature - The temperature of the discharge water ranged from 27°C in July to a minimum of 8°C in January. Other studies (7) have indicated that 16°C may be the lower limit for efficient denitrif ication. This experiment, however, did not show any correlation between temperature and nitrate reduction or if there was an effect it was masked by other factors. Energy Source Requirements - The theoretical straw require- ment can be calculated using a formula derived from work by P. L. McCarty (10). A quantity of organic waste with an oxygen equiva- lent (Oe) of 2.86 pounds would be required to convert one pound of nitrate-nitrogen into nitrogen gas. However, in the biological 20 process, a minimum of 2 5 percent of the added organic material, is used by micro-organisms for cell synthesis and is therefore unavail- able for denitrif ication. Where the organic source is not easily broken down, such as the barley straw used in this study, probably no more than 50 percent of the material will be available for deni- trif ication. Thus in practice an organic waste with an Oe of 2.86/ .50 or 5.72 pounds is required per pound of nitrate-N. In addition, some organic material must be added to create the anaerobic condi- tions required for denitrif ication. This requires about 1.5 pounds of Oe per pound of dissolved oxygen (DO) in the incoming drainage water. In summary the organic oxygen equivalent required (0^.) for denitrif ication can be expressed as follows: Or - 5.72 (NO3-N) +1.5 (DO) If we assume that there will be 20 milligrams per liter of NO3-N and 8 parts per million of dissolved oxygen in the drainage water theoretical barley straw requirement for denitrification of this water can be calculated from the above formula as follows: Or - 5.72 (pounds of NO3-N per AF) +1.5 (pounds of DO per AF) Or - 5.72 X 54.4 + 1.5 X 21.7 - 343 pounds per acre-foot In a like manner the theoretical barley straw requirement for the pond study can be calculated from the above formula. If we assume that the average NO3-N concentration was 10 mg/1 and the dissolved oxygen content of the water was 8 parts per million the calculations are as follows: Or - 5.72 X 22.7 + 1.5 X 21.7 - 153 pounds per acre foot Using this quantity and the various flow rates during the study period the theoretical daily straw requirement ranged from 41 pounds for the 60 gpm flow and the 2 days detention time to approximately 14 pounds for the 20 gpm and the 6 days detention time. The straw requirements for all of the flow rates and detention times are listed in Table 4. According to these calculations the amount of straw, about 50 pounds per day, actually added to the trench should have been more than adequate to provide energy for complete deni- trification of the system. That complete removal did not always take place can probably be attributed to the fact that a readily decomposable form of the straw did not come into the contact area because of the mat of soil and straw floating on the water surface. Electrical Conductivity - The concentration of total dis- solved solids as measured by the electrical conductivity of the 21 water varied during the season from about 300 to 2900 micromhos and was primarily dependent upon the concentration of the supply water rather than any variation as a result of changes within the system. The low concentrations were during the periods of large water releases from the Delta-Mendota Canal into the wasteway and the high concentrations were during periods when all the water in the wasteway was from seepage. Although there were evapotranspira- tion losses they were not large enough to be measured by the con- ductivity method used in this study. Table 4 Flow rates, detention times and straw requirements of deep pond. Detention Straw Flow Time Requirement GPM Days lbs/day g 10 mg/1 NO3-N 60 2.0 41 36 3.3 25 34 3.5 23 30 4.0 20 20 6.0 14 Grass Plot Study The shallow pond investigations were made on an 8.3 acre plot designed to simulate a section that could be incorporated into the Kesterson Reservoir. Methods and Materials - The plot was rough leveled, bordered and checked at . 3 foot contour intervals. A layout of the plot is shown in Figure 1. Water grass, Echinochloa crusgalli , was planted in the plot at the beginning of the study. The grass was to be the carbon energy source for the denitrif ication process. The first year it was mowed and left in the field. The mowing did not appear to increase the denitrif ication rate therefore the practice was discontinued. The water source for this study was the same as that for the deep trench. Supplemental nitrate was added to the supply water in the manner detailed in the previous study. Sodium nitrate rather than calcium nitrate was used as the nitrate source during a part of the study in an attempt to reduce the percolation losses from the plot. 2^ During the greater part of the investigation the plans were to maintain the nitrate -N levels at about 16 mg/1, however, due to variations in the water and supplemental nitrate-N flows the actual concentrations ranged from about 7 to 70 mg/1. In order to evalu- ate the nitrate reduction rate of water of higher nitrate -N con- centration the levels were increased to about 50 mg/1 for about 32 days between April 6 and May 8, 1970. A continuous flow of water through the plot was maintained with an average depth of approximately six inches. The rate of flow of the water was monitored with Parshall flumes as it entered and left the plot. The maximum flow to the plot was limited by the size and gradient of the supply ditch and because of this the average depth of water was not varied. This flow, approximately 400 gallons per minute, was maintained throughout most of the study. As the water moved through the plot there was a reduction in flow due to evapo- transpiration, seepage, and percolation losses. These losses were assumed to be constant through the plot and were taken into con- sideration in calculating the detention times. The outflow varied from about 30 gallons per minute during the peak evapotranspiration period in the summer to about 140 gallons per minute during the minimum evapotranspiration period in the winter. The inflow rates and the theoretical detention time for each check during represen- tative periods in the summer and winter are listed in Table 5. Results - The concentrations of the nitrates in the water at the inlet of the plot, the outlets of checks 2 and 4, and the out- let of the plot are graphed in Figures 4 and 5. The data show that as the water moved through the plot there was a reduction in the nitrate concentration. This reduction continued until it reached the outlet of check 4, after this point generally there was no significant change. During the study the amount of nitrate removal varied from almost complete reduction to only about 50 per- cent reduction. The maximum nitrate -N removal occurred in the summer and early fall months when there was maximum grass growth and during the late winter months and spring after the grass had died back, as a result of killing frosts and had fallen into the water. The least reduction occurred during the months of November and December. The nitrate -N concentration during the maximum reduction period was reduced from the average 15 mg/1 to less than 2 mg/1. During the periods of lesser reduction the concentration at the outlet at times ranged up to about 4 mg/1 of nitrate -N. The reduction pattern and rates were relatively consistent for the two years that the tests were conducted. The main emphasis of the study was placed on the removal of nitrate, the principle nitrogen form in the drainage water, however, any treatment system must be concerned with the removal of the total nitrogen content of the water. The concentration of other nitrogen 23 1/6W N-31VailN n/6w N-31VdllN 24 l/6lN N-31VH1IN l/f>W N-31VailN 25 forms, nitrite, ammonia and organic N were generally low in both the influent and effluent waters. However, there were periods during the winter months when there was evidence, as noted in Table 9, that the total nitrogen content, especially the organic -N in the effluent was greater than the allowable maximum nitrogen dis- charge rate for the Delta of 2 mg/1. Table 5 Calculated Inflow Rates and Theoretical Detention Times of the Various Checks in the Grass Plot Check No. Area Ave. Flow Rates Detention Time ( Days) Acres GPM Per Check Accumulative Summer Winter Summer Winter Summer ' Winter 1 0.27 400 400 0.1 0.1 - - 2 1.31 370 390 0.4 0.4 0.5 0.5 3 1.26 330 350 0.5 0.4 1.0 0.9 4 2.79 270 310 1.5 1.2 2.5 2.1 5 1.56 140 220 1.5 0.9 4.0 3.0 6 0.86 70 170 1.6 0.7 5.6 3.7 Outlet 30 140 Total 8.05 5.6 3.7 When the supply water in which the nitrate -N concentration had been increased to 40 mg/1 moved through the plot, there was a gradual reduction of the nitrate -N until at the outlet it had been reduced to about 1-4 mg/1. At this time we can only theorize as to the cause of the variation in the removal rates, especially as to the greater reduction in the colder winter months with the diminished grass cover. The best explanation would seem to be that after the grass has died back and lodged, much of the plant matter is deposited in the water near the bottom of the ponds where the material is more rapidly decom- posed thus resulting in a relatively large available carbon source. As the grass decayed there were more open spaces on the water sur- face which might be expected to encourage an increase in algae growth thus accounting for some of the nitrate reduction by an in- crease in organic nitrogen in the algae plant cells. Algal deter- mination made in February 1970 indicated that there was a decrease in the algal count as the water moved through the plot. The genera 26 and the estimated number of cells per milliter at several stations in the plot are listed in Table 6. Tests for nitrite, ammonia and organic nitrogen indicate that, gen- erally, there were small amounts of these N forms present however with the exception of some of the winter months there were no signi- ficant increase in these quantities as the water moved through the plot. Table 6 Algae Count at Several Sampling Sites in Grass Plots - February 26, 1970 Sample Genus Cells/ml Inlet Diatom-Nitschia Diatom-Amphiprora Diatom-Diatoma 2,500 500 3,000 Check 2 Diatom -Diatoma 4,000 Check 4 Diatom-Diatoma 1,000 Outlet Diatom-Diatoma 500 During the months in which there were increases in the total organic N at the outlet as compared to the inflow water these increased amounts were a relatively small portion of the total losses. There was no evidence that at any stage of the study there was a recycling of the lost nitrogen. This would suggest that denitrif ication with its resultant loss of nitrogen gas accounts for most of the nitrates removed. The concentration of various forms of nitrogen at several dates during the study are listed in Table 7. Dissolved Oxygen - The changes in the dissolved oxygen content of the water as it moved through the plot were inconsistent. Generally, during the warmer periods when there was a good cover of grass over the ponds there was a reduction of the dissolved oxygen. During short periods of time when the reduction was at its peak, the DO was reduced from an average of about 8 to about 1 mg/1. Normally the reduction was at a lesser rate, with the maximum removal about 60 percent of the total. After December when there was very little grass still standing in the ponds the reduction was negligible. There was a fair correlation between the percent removal of DO and nitrates during the warmer months. At other periods there was no obvious correlation between the two parameters. During the late winter and early spring months there was almost complete removal of the nitrates but there was no significant reduc- tion in the measured DO content. This fact would appear to be a 27 ^^l^o^^OQ0^^O^O^ ,o~*-*~*^'^ r-inO(Ni-j-jrsiooooo^-»mt7v-o^ OoO^Joo-oooct^O-OOct^O momoooooooomu-iinoo OOOOOmmoOOOO OO-O-a-CM ****0~*0r-inr~-o0r^ iiiiiiii 00 -o o OOOO"— »•—<•— 'U^CT^O i^oOii^r>i(Ni OOC10aOO<^"^'AO--~JO 0030 m^ -jom— ■ <->J<.i< aiuj^j^ VUj^Jd «uj-IOO0l-IOCJ0l-lOO0>-40 3 cxx3Cj:x:3Cxj:3 O i-iUOOi-" 0.2 lbs. - ave. daily N release from decomposition of plant material « 16 X 1.8 X 2.72 + .2 - 78.5 pounds (a) No - Ni Nq » 78. 5 pounds (c) No - Ds + Dp -t - Pd +1 + D + Dp + I - Pd - Cnd Qd 1^ Where C^d ^ N concentration of deep pecolation Qd ^ Quantity of deep percolation Pd Check # 1 - 15 X .11 X 2.72 ^4.5 pounds Check H 2 - 13 X .16 X 2.72 » 5.7 pounds Check # 3 - 10 X .19 X 2.72 - 5.2 pounds Check # 4 - 5 X .42 X 2.72 » 5.7 pounds Check # 5 - 3 X .23 X 2.72 »= 1.9 pounds Check # 6 - 2 X .14 X 2.72 » .8 pounds Pd » 23.7 pounds - 1 X .38 X 2.72 - 1.0 pounds Dg + Dp +1 - 78.5 - (23.7 +1.0) "= 53.8 pounds per day The 53.8 pounds per day calculated here is that amount removed from the surface water. In addition to these losses, the studies indi- cate that the greater portion of the nitrogen in the water that percolates into the soil is also removed by denitrif ication. If time permits later studies will be designed to delineate that portion removed by each of the parameters; denitrif ication in the water, denitrif ication by plant decay and immobilization in an organic form. A water balance can also be calculated for a system such as the grass plot using the formula: Qi " Qp+ Qe + Qc + Qo Where Qi - total inflow (A.F.) Qp » deep percolation (A.F.) Q^ »= surface evaporation losses (A.F.) Qc ■= consumptive use (A.F.) Qo " surface outflow (A.F.) 32 In the shallow grass plot investigations all of the items except Op can be measured or calculated, therefore, if we want to solve for this factor for an average 24-hour period, the formula becomes; Qp - Qi - (Qe + Qc +Qo) Where Q^ - 1.90 A.F./day Qe - .1 A.F./day Qc - -07 A.F./day Qo - .38 A.F./day Qp - 1.80 - (.1 + .07 + .38) « 1.25 A.F./day 33 SECTION VI COST ANALYSES Preliminary cost analyses were prepared of the two methods studied in this investigation to gain some concept of the cost of these methods in comparison to those studied in other phases of the pro- gram. The requirements were based on data obtained from the plot study and may be subject to revision upon more complete investiga- tion. The reconaissance design and cost estimates were prepared by the Bureau of Reclamation Regional Engineer's office. The values listed include design, construction, materials, contingencies and all indirect costs. The land values were based upon the costs of unimproved, native pastures within or near the Grasslands area. The determinations of the costs of treatment by the two systems were based on the premise that the ultimate maximum drainage out- flow from the San Luis Service Area had been reached and all treatment facilities were in operation. The maximum daily flow which the systems must treat will be 300 cubic feet per second and the total annual output will be about 155,000 acre feet. It is estimated that this maximum flow will be reached about thirty years after the start of operations. In actual practice, it may prove more economical to construct the facilities in stages as the drainage flows builds to maximum. The land requirements for the treatment systems were based on criteria derived from the deep pond and grass plot studies. The deep pond system required approximately .09 acres to remove the nitrogen from .15 acre feet of drain water per day. This would be equivalent to 337 acres to treat the ultimate maximum drain flow of 300 cubic feet per second. As the nitrogen concentration of the water used in this study was only about 50 percent of the 21 mg/1 projected to be in the San Luis Drain water, the pond area requirement was increased to 545 acres to make the costs equivalent to actual conditions. An additional 20 percent or 125 acres, was added to the land requirements for ditches, levees, roads and working areas. The total area requirement for this method would be approximately 800 acres. The shallow ponds required approximately 5.5 acres to treat 1.57 acre feet. This would be equivalent to about 2,080 acres required to treat the maximum flow of 300 cubic feet per second. Assuming an additional 20 percent of this area would be required for supplemental land uses, the total land require- ment for the grass plots method will be approximately 2,500 acres. Additional criteria used to estimate the costs of the two systems were as follows: 1. All costs were based upon January 1970 dollar values. 35 2. Capital and land costs amortized over 50 year period at 5% interest. 3. Capital costs include an engineering and contingency factor of approximately 56 percent. 4. All lands were purchased at start of the project at $500 per acre. 5. Electric power costs were calculated at 1<:/KWH. 6. Replacement costs were calculated on all material items on a sinking fund basis over a 50 year period at 5 1/8 percent interest. 7. Post treatment for algae removal would be required. 8. Based on costs of rice production as modified to fit specialized requirements. 9 . Costs per acre foot treated were determined by dividing the total annual costs by the projected ultimate annual flow. Based on the above criteria it was estimated that the deep pond denitrification would cost approximately $14.00 per acre foot or $43.00 per million gallons. The shallow grass pond method would cost about $6.50 per acre foot or $20.00 per million gallons. Lists of the various cost items appear in Tables 10 and 11. If it is determined at a later date that post treatment of the water for algae removal is not necessary the cost can be reduced by approxi- mately $2.00 per acre foot or $6.00 per million gallons. Also if the operation of the systems is found to be compatible with the proposed use of Kesterson Reservoir additional savings in land acquisition and preparation costs may be realized. Schematic layouts of portions of the systems are presented in Figures 6 and 7. 36 Table 10 Estimated Cost for Removal of Nitrogen by Deep Pond Method Number Item Cost Capital Costs Nitrogen Removal 1 Materials, Installations, Contingencies and Engineering $22,800,000 2 Land Costs (800 acres g $500/acre) $ 400,000 Subtotal $23,200,000 Post Treatment 3 Algae Separation Facilities $ 5,370,000 Total Capital Costs $28,570,000 Annual Costs 4 Ammortization of Capital Costs (50 yrs. @ 5%) Nitrogen Removal $ 1,270,000 Algae Separation $ 290,000 5 Replacement Costs (Sinking Fund @ 5-1/8% Interest) $ 10,000 6 Operation, Maintenance and Administration $ 200,000 [y^ 7 Power Costs @ Ki/KWH $ 30,000 8 Material Costs (Barley Straw % $15.50/ton) $ 400,000 Total $ 2,200,000 Cost per acre foot $ 14.00 Cost per million gallon $ 43.00 37 Table 11 Estimated Costs for Removal of Nitrogen by Shallow Grass Plot Method Number Item Cost Capital Costs Nitrogen Removal 1 Materials, Installations, Contingencies and Engineering $ 7,240,000 2 Land Costs (2,500 acres @ $500/acre) $ 1,250,000 Subtotal $ 8,490,000 Post Treatment 3 Algae Separation Facilities $ 5,370,000 Total Capital Cost $ 13,860,000 Annual Costs 4 Ammortization of Capital Cost Nitrogen Removal Algae Separation 5 Replacement Costs (Sinking Fund @ 5-1/8% Interest) 6 Operation, Maintenance and Administration 7 Power Costs 1<:/KWH Total Cost per acre foot Cost per million gallons $ $ 470,000 290,000 $ 10,000 $ 200,000 $ 30,000 $ 1,000,000 $ 6.50 $ 20.00 38 '^TJ -I LEGEND I ¥ L L ! ^1 I- StU LUIS 0»JH»l^ '"»' rni u 14" !• }0* «M l=^i 4 '\ 1^ TYPICAL 1200' UNIT FIGURE 6 — DEEP TRENCH NITRATE REDUCTION PONDS 39 LEGEND 4* ^trf »••••« m** 9 KM' C*H«ct*r Drew (CtM*< »««l «' •• 14* B« Mata C«l)*ct«ri ( 0«Wi ■nil*** I OH*l c«l W MO cfl P«M| «.*M 9>4* FICURE 7 -SHALLOW NITRATE REDUCTION PONO TYPICAL ««. MILE tfCTIOM 40 SECTION VII Discussion These investigations were initiated as empirical studies to deter- mine if denitrif ication could be induced by utilizing facilities somewhat similar to the San Luis Drain and the Kesterson Reservoir and using agricultural waste products or plants grown in place as the organic carbon source. When it was determined that it was possible to reduce the nitrate concentration by these means, the investigation was extended and refined to more precisely define parameters such as denitrif ication rates, optimum operating con- ditions, design criteria and costs. Because of the problems in- herent in quantifying data from a relatively large field-size study the results were not always conclusive. However, although the many ramifications of the processes could not always be explained, it was evident that substantial percentages of the nitrates can be removed by these methods. Air pollution control recpulations in Fresno County (12) designed to promote environmental enhancement place restrictions on burning of stubble. These regulations will undoubtedly become more restric- tive with time and will force growers to find other means to dispose of their straw. The use of the straw in a denitrif ication process would serve as one means of disposal. Cost of the straw to the project should be no more than baling, transportation expenses, and residue removal after oxidation. When the estimated peak drainage flow of 300 cubic feet per second is reached the daily straw requirement would be approximately 100 tons per day. The ultimate annual requirement for the estimated 155,000 acre-feet per year outflow will be about 26,000 tons. This would be equivalent to the straw yield from approximately 13,000 acres of grain. Denitrification by the grass plot method or variation of this method shows considerable promise. Although the lack of suitable controls prevented precise evaluations of all causes and effects in the system, the empirical results indicate that the denitrifica- tion process will take place under the conditions studied. In the simple system in which water flowed across a grass covered field, it was demonstrated that the nitrate concentration during part of the year can be reduced to less than 2 mg/1 nitrate -N. This level would meet the minimum standards for discharge into the Delta. At other times it would be necessary to store and recycle the water or treat the effluent with a more precisely controlled method. The investigations indicated that water could be treated in shallow grass plots at the rate of .15 cubic feet per second per acre. At this rate approximately 2,000 acres of ponds would be required to service the 300 cubic feet per second of ultimate peak flow in the San Luis Drain or approximately 6,000 acres to treat an outflow of 1,000 cubic feet per second, the projected ultimate drainage outflow from the San Joaquin Valley. These estimates were based on the 41 assumption that the experimental criteria derived from the test site can be extrapolated to a large scale system. In addition to the land required for the ponds additional areas will be required for ditches, roads and other service areas. The total land require- ment to treat the flow from the San Luis Service Area would be approximately 2,500 acres. Several variations of this plan might be implemented. At this time the most feasible method would seem to be to incorporate the shallow ponds into the Kesterson Reservoir area. This would permit many of the facilities and structures, already designed into the Reservoir to be used in the denitrification plan and yet not essentially change the main purposes for which the Reservoir was designed. Some supplemental facilities would have to be installed such as additional contour checks, flow control structures, ditches, and pumps. A layout of a typical section of ponds is shown in Figure 7. If no satisfactory arrangement can be worked out to use the Kester- son facilities, it would be necessary to purchase additional lands for the denitrification. The most logical location for these would be in the Grasslands. A variation of this plan would be a system in which denitrification of surface flows was supplemented by denitrification in percolating waters through the soils. In this plan a drain system would be installed beneath the ponds. at a depth near 42 inches. These drains would be designed so that they would be submerged at all times. Infiltration would be encouraged and the percolating waters collect- ed in the field drains and returned to main collector system. This plan would require additional construction expenses for the drain installations, however, the present studies indicate that this method gives more consistent and complete nitrate removal than any other type investigated. Another alternative of this plan would be to reach an agreement with the Grasslands Soil Conservation District to cooperate in their "Master Plan for Land and Water Use in the Grasslands of Western Merced County California" (13). This agency has authorized a series of studies to investigate the feasibility of a program to enhance the wildlife program of the area. The major objectives of this plan are to import sufficient water of reasonable quality to provide a year round program to assist in developing a grazing plan consistent with wildlife and livestock and improve the migratory waterfowl habitat vital to the maintenance of the Pacific Flyway. Studies have indicated that the area could use approximately 400,000 acre-feet of water during the peak use months of June, July and August (14). The Grassland Soil Conservation District presently 42 has a contract with the water districts of the area to the affect that it will accept drainage water with total dissolved solids up to 3,000 parts per million (14). If the waters in the San Luis and master drain could meet these standards it might be advantageous to seek an agreement with the Grasslands to deliver these waters to that area. The nitrates in the water moving through the native and pasture grasses on these lands should be reduced in essentially the same manner as in the grass plots study. After the water has moved through these grasslands any runoff water could be collected into the Kesterson Reservoir. The northern (lower) boundary of the Grasslands Water District joins the southwest boundary of the Kesterson Reservoir, therefore, it would be relatively easy to collect the excess and presumably denitrified runoff water into Kesterson Reservoir. At this point such a plan is purely speculative and may be in conflict with some of the purposes of the drainage program, however, it would appear to have sufficient merit to warrant further investi- gation whenever all parties have firmed up their plans. 43 SECTION VIII ACKNOWLEDGEMENTS Mr. Robert J. Pafford Regional Director Region 2 Bureau of Reclamation U.S. Department of Interior Board of Directors Mr. Paul De Falco, Jr. Regional Director Pacific Southwest Region Water Quality Office Environmental Protection Agency Program Coordinator Mr. John Teerink Deputy Director State of California Department of Water Resources Resources Agency John Maletic Chief, Land Resources Branch Engineering and Research Center, USBR, Denver Conducted By John Williford Research Soil Scientist, USBR, Fresno Under Direction Of John Bailey. . . Doyle R. Cardon. Chief, Land Resources Branch, USBR, Sacramento Head, Land Use, Drainage, and Economic Section, USBR, Fresno Assisted By Joseph Cummings Natural Resources Specialist Ben Nakamura Soil Scientist Nels Edquist Natural Resources Specialist Dave Smolen Natural Resources Specialist George Theiss Soil Scientist John Wessies Soil Scientist Don Nelson Physical Science Technician Maryellen Ceja Typist Gerry Smith Typist Buddy Smith Cartographic Technician USBR USBR USBR .USBR USBR USBR USBR USBR USBR USBR John Williford John A. McKeag Report Prepared By . .Research Soil Scientist, USBR, Fresno Special Acknowledgement To Drainage Specialist (Retired), USBR, Sacramento 45 SECTION IX REFERENCES (1) Johnston, W. R. , Ittihadieh, F., Daum, Richard M. , Pillsbury, Arthur F. , "Nitrogen and Phosphorous in Tile Drainage Efflu- ent," Soil Sc. Soc. Ameri. Pro., Vol. 29, p. 287-289, 1965. (2) State of California, Department of Water Resources, "San Joaquin Valley Drainage Investigations, San Joaquin Master Drain," preliminary edition. Bulletin No. 127, Jan. 1965. (3) Goldman, Joel C, Arthur, James F. , Oswald, William J., Beck, Louis A. "Combined Nutrient Removal and Transport System for Tile Drainage from the San Joaquin Valley", Agricultural Waste Water Treatment Center, Firebaugh, Calif., Dec. 1969. (4) Nightingale, Harry, Personal Communication, ARS, U.S.D.A., Fresno, California, Sept. 1959. (5) Cole, R. C, et al, "Soil Survey, The Los Banos Area, Califor- nia", U.S.D.A., p. 58, 1952. (6) Instruction Manual, Nitrate Ion Electrode Model 92-07, Orion Research Inc., Cambridge, Mass., 1967. (7) "Standard Methods for the Examination of Water and Wastewater", American Public Health Association, Inc., New York, N.Y., 12th Ed. 1965. (8) Reclamation Instructions, Release No. 577-1 U.S. Department of the Interior, Bureau of Reclamation, Office of Chief Engineer, Denver, Colorado, 1967. (9) Connel, W. E., and Patrick, W. H., Reduction of Sulfate to Sulfide in Waterlogged Soils, Soil Sc. Soc. Amer. Pro. Vol. 33, 1969. (10) State of California, Department of Water Resources, "Field Evaluation of Anaerobic Denitrif ication in Simulated Deep Ponds", Bulletin No. 174-3, May 1969. (11) Mikkelson, D. S., Finfrock, D. C, Miller, M. D. , "Rice Fertilization", California Agric. Exp. Sta. University of Calif., Davis, Leaflet 96, June 1958. (12) Fresno County Air Pollution Control District, Rules and Regulations, Fresno, Calif., June 2, 1969. 47 (13) M & L Engineering "Master Plan for Land and Water Use in the Grasslands of Western Merced County, California, "Phase III, Los Banos, Calif., 1967. (14) Dickey, G. L., "Master Plan for Land and Water Use in the Grasslands of Western Merced County, California", Phase I, U.S. Soil Conservation Service, Fresno, California, Unpublish- ed Data. I'EBNMENT PRINTING OFFICE 1972— 484-484/140 48 u Accession Numbc ry I Subject Field tc Group 05-D SELECTED WATER RESOURCES ABSTRACTS INPUT TRANSACTION FORM ^ Organization Department of Interior — I Bureau of Reclamation Fresno Field Division Fresno. California TECHNIQUES TO REDUCE NITROGEN IN DRAINAGE EFFLUENT DURING TRANSPORT JQ ]Author(s) Williford, John W. Cardon, Doyle R. tj: Project Designation I3O3OELYO6/TI-IO 21 22 Agricultural Wastewater Studies, 1971 Report No. REC-R2-71-ia Pages 48 Figures 7 Tables 11 References 14 •\'\ I Descriptors (Starred First) *Waste Water Treatment, *Nitrates, *Denitrification, *Agricultural Waste, Algae, Anaerobic Bacteria, Dissolved Oxygen, Dissolved Solids, Cost Analyses ?5 (Starred First) *San Luis Drain, California, *Kesterson Reservoir, *Nitrogen Reduction, Detention Times ^ A bstrac t Three methods to remove nitrates from the agricultural drainage water from the San Luis Service Area were investigated. One method was a theoretical evaluation of nitrate removal by algae during the transport of the drainage water in the San Luis Canal or- during storage in the Kesterson Reservoir. The other methods were designed to promote anaerobic bacterial denitrification in a continuous flow of drainage water. One method used barley straw and the other water grass grown in shallow ponds as the carbon energy source. The barley straw was placed in a trench about 10 feet deep and the nitrate removal rate determined under various flow and detention rates. The water grass was grown in ponds under a continuous flow of water of about 4 to 5 inches depth. Under optimum conditions both methods reduced the nitrate -N concentration of the drainage water from a maximum of about 30 mg/1 to less than 2 mg/1. The~ cost of nitrogen removal by the shallow grass plot systems, the most economical and feasible method investigated, was estimated to be $6.50 per acre foot or $20.00 per million gallons. U. S. Bureau of Reclamation RCES SC'£> >lGTO^^: D. C. 20J4 I ric tN FO^^ l9«»-33>-33 A> M H-* rt »^ g-B.^ (5 ►^ < o o o «*• c 2, i *' ^ o. ft. O o — n a 08 J" >>; D. " is ^ tj 3 tn r» It ° s °8 S- 3 f5 - c. W " -2. a. cr S. e- g. 2 « n • s v> S J- W » s- B K" a "i S " n U s- u z 3) 3D TJ < » c 3) c CT (O* (D 0' Z 3- 00 Q) §: m 0" W z -1 «^ CD X 3 (A Z H > r- c _i to "0 (0 o> 3) 5' 0) * O" (D X c H (A i •-» m CO 5* •< 0' a> 3 H N) tn ■sj (D Z 0> i > Nj a> (0 3 m Z -< i® 87^4 3} -D Z W 2 H m > z H m > > r- Z -0 3} m H m m C/) H TJ > Z > m Z -< THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW BOOKS REQUESTED BY ANOTHER BORROWER ARE SUBJECT TO RECALL AFTER ONE WEEK. RENEWED BOOKS ARE SUBJECT TO IMMEDIATE RECALL T n use i ^ ^%h f^"^^ JAN 1983 t.ov 2 ma LIBRARY, UNIVERSITY OF CALIFORNIA, DAVIS Book Slip-Series 458 3 1175 00499 7766 TC California. 82I4 Biaietin. C2 A2 A^ /7¥ ^VJ PHYSICAL SCIENCES LIBRARY Dept. of Water Heaources,