Progress 10/28/14 to 09/30/19

Outputs
Target Audience:Our target audiences include local water agencies and resource conservations districts as well as environmental groups, and state regulatory agencies. To that end, we have made presentations about this work at local conferences as well as publishing in local and national periodicals. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?We have trained two PhD students (one completed, one nearing completion) during this project while providing opportunities for some UG students to prepare reports. How have the results been disseminated to communities of interest?Yes; through regular publications every year of project. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Changing climate conditions and continued salinization of soils and groundwater are persistent threats to irrigated agricultural production and groundwater supplies in the western states. Our goals under this multi-state project were associated with (a) characterizing the bio-physical (soils, crops, hydrology and climate) and socio-economic factors that influence water­ use decisions and related market or non-market outcomes; and (b) developing or enhancing quantitative methods to address related emerging water management issues. Our work followed two general tracks to address these goals including; (a) assessment of salinity and related impacts on crops and groundwater use in the Salinas and Central Valleys of California, and (b) development and evaluation of novel wastewater treatment methods designed to enable treated wastewater reuse in agricultural production. Beneficial use of treated or recycled wastewater is increasing especially that used in irrigated agriculture as a means of alleviating demands on freshwater resources and meeting groundwater sustainability goals and efforts to limit seawater intrusion to groundwater aquifers. We evaluated recycled water use for agricultural production during more than two decades in the Salinas Valley of California using both field monitoring of soils and creation of a soil-water-salinity model to consider the key factors controlling rootzone salinity in the field. We found that improving irrigation efficiency alone, without limiting expansion of irrigated acreage results in increased salinization and water use in the Valley. Including likely climate change conditions, modeled results provided insights into possible regional water management strategies that might be deployed to limit further salinization while maintaining agricultural production at acceptable levels. We also found that previous regulatory and related infrastructure development efforts, while effective in the short term (2-4 years) in reducing groundwater overdraft in the Valley, were ultimately unsuccessful in sustaining that benefit as growers adapted and new water uses developed. Thus new approaches are needed towards achieving sustainable groundwater management that limits environmental and agricultural degradation while enabling agricultural production sufficient to maintain socio-economic conditions in the Valley. With respect to developing relatively low-cost wastewater treatment methods to remove excess nitrates, we adapted a zeolite-aggregate percolation bed under a range of loading, aeration and nutrient conditions to remove the nitrates with minimal energy and management requirements while also reducing greenhouse gas emissions. After demonstrating the relative success, ease of use and low cost of the zeolite-anammox treatment systems, we have been deploying them around the greater San Francisco Bay area and in Oregon to help generate recycled water to be available for other uses.

Publications

• Type: Journal Articles Status: Awaiting Publication Year Published: 2019 Citation: Zikalala, P., I. Kisekka, and M.E. Grismer. 2019. Hydrological processing of salinity and nitrate in the Salinas Valley agricultural watershed. Env. Monitoring & Assessment
• Type: Journal Articles Status: Under Review Year Published: 2020 Citation: Zikalala, P., M.E. Grismer, L.M. Ahiablame, B. Lampinen, B. Chen and I. Kisekka, and. 2020. Quantifying the effects of climate variability on almond yields in California's Central Valley using Dynamic Factor Analysis. Plos1
• Type: Book Chapters Status: Awaiting Publication Year Published: 2020 Citation: Grismer, M.E. 2019. Irrigation Hydrology - Landscape, Scales and Social Context. In: Handbook of Irrigation Hydrology and Management, Ed. By S. Eslamian. Taylor & Francis Press- in-press.
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Zikalala, P., I. Kisekka, and M.E. Grismer. 2019. Calibration and global sensitivity analysis for a salinity model used in evaluating fields irrigated with treated wastewater in the Salinas Valley. Agriculture, 9(2):31. doi:10.3390/agriculture9020031.
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Grismer, M.E. and P.G. Zikalala. 2019. Recycled water use, water demand and infrastructure in the Salinas Valley, CA. ASA California Plant & Soil Conference Proc. pp. 18-28.

Progress 10/01/17 to 09/30/18

Outputs
Target Audience:Our target audiences are largely environmental groups, regulatory and resource agencies and cooperating Wastewater Treatment Plants (WWTPs); in particular we are working with the Monterey Recycled Water Agency in Salinas related to our agricultural water quality impacts assessments and with various Easy San Francisco Bay WWTPs with respect to developing low-cost wastewater treatment strategies directed at increasing water re-use capacity. In addition, we have made presentations related to the Salinas work to UC-ANR and the ANR-Israel workshop in Davis as well as the Sunrise Rotary in Sebastopol. We also have submitted presentation papers for the ASA-Fresno Conference in February 2019 and for the INternational Wastewater Conference in Edinburgh, UK in June 2019. Changes/Problems:Several do not accept that the zeolite-anammox treatment process is actually associated with anammox bacteria so we are obtaining additional DNA analyses of zeolite biofilms and will present that information at an upcoming international Conference. In the Salinas Valley, some data collection continues to be challenging as well due to limited access either physically or politically; we are working with cooperators wherever possible. What opportunities for training and professional development has the project provided?One PhD student completed her dissertation this past year and another PhD candidates is working on these projects. How have the results been disseminated to communities of interest?We have made presentations about the Salinas work to UC-ANR and the ANR-Israel soil salinization workshop in Davis as well as the Sunrise Rotary in Sebastopol. We also have submitted presentation papers for the ASA-Fresno Conference in February 2019 and for the INternational Wastewater Conference in Edinburgh, UK in June 2019. What do you plan to do during the next reporting period to accomplish the goals?We plan to continue our assessments of the zeolite-anammox treatment process at cooperating WWTPs and have joined with researchers at the UC DAvis Genome Center to help us better characterize the biofilm microbial communities. We are also working on a long-term evaluation through modeling and historic assessment of agricultural development and water policies in the Salinas Valley during the past century to better inform practices and policies into the future anticipating changing climates conditions.

Impacts
What was accomplished under these goals? Beneficial use of treated or recycled wastewater is increasing in California especially that used in irrigated agriculture as a means of alleviating demands on freshwater resources and meeting groundwater sustainability goals. Recycled water use for agricultural production began some two decades ago in the Salinas Valley of California as part of efforts to limit seawater intrusion to groundwater aquifers while exploring the possibility of alternative water supplies for agriculture in the Valley. Concerns remain about rootzone salinity accumulation and salt loading to groundwater and surface water resources. Meanwhile, at least three other key interacting drivers affecting water resources availability and quality in the Valley are in play. These include evolving water agency policies and infrastructure, and grower shift towards greater vegetable/lettuce production to meet market demands and adoption of more efficient irrigation technologies leading to greater irrigated acreage across the Valley. Water resources (surface and subsurface) availability and deterioration, as well as rootzone degradation, remain the major factors limiting the environmental sustainability of irrigated agriculture in the Valley. Typically, increased soil salinity occurs during the growing season as crop water demand leaves irrigation applied salts in the soil followed by winter rains that leach the soil profile salts to deeper depths. Excess rootzone salinity is managed by adjusting irrigation applications using leaching requirement concepts that rely on applied water and existing soil salinity (Letey et al., 2011). Salinity risks increase when using saline water for irrigation and when poor fertilizer and poor irrigation management are combined. Adoption of more efficient irrigation application methods alone at the farm-scale may not address the salinization problem of soil rootzones or subsurface water supplies if there is not an associated decreased total water/salt application at the regional or Valley scale (Grafton et al., 2018). However, growers may have limited trust in the agencies promoting particular water policies and tend to doubt that these policies or practices lead to improved water quality or availability (Drevno, 2018). These trade-offs suggest a need to develop new irrigation guidelines for adaptation to these changes within the context of sustainable water use (including groundwater) across the basin. Surface runoff and leaching are two major transportation pathways for applied salts to degrade surface and subsurface water resources. Groundwater salinization associated with leaching and seawater intrusion diminishes groundwater quality in several water supply aquifers along the California coast (Konikow and Rielly, 1999) and in the Salinas Valley the lower Salinas River from Gonzales to the estuary is listed (EPA 303d) as impaired for salinity and this salinity threatens both water supply and sensitive riparian and estuarine ecosystems. Among several previous actions directed at sustaining groundwater and developing surface water resources in the Valley, the Monterey County Water Resources Agency (MCWRA) passed an ordinance in 1995 prohibiting groundwater extraction due to ongoing problems of seawater intrusion into the two major aquifers below Salinas and Castroville. In 1998, Monterey County Water Recycling Projects (MCWRP) began delivering recycled water (tertiary-treated wastewater) to 12,000 acres in the northern Salinas Valley. By 2010, the agency had also completed the Salinas River Diversion Facility enabling greater access to surface water rights and reduced groundwater pumping. Similar such efforts continue and are largely directed at maintaining the key economic driver in the Valley. Irrigated crop production in the Salinas Valley is a valuable output (growing from $2.7 to $3.6 billion from 1997 to 2017) while the associated saline water drainage and runoff are key liabilities recognized by water resources managers. Crop values in 2017 alone for leaf lettuce and berries were $830 and $686 million, respectively (Monterey County Crop Reports, 2017). Here, we are interested in the interplay between market-driven crop production, adoption of more efficient irrigation technologies and various water policies and infrastructure adopted or constructed in the Salinas Valley and their effect on the long-term sustainability of groundwater resources and rootzone salinity. As we described previously, use of treated wastewater for irrigation is emerging reality that depends largely on the availability of low-cost treatment processes capable of removing both pathogens and nutrients. We continue to explore use of the zeolite-anammox process for wastewater treatment under a variety of conditions that include wastewater strength, aeration and iron supplementation. Further, we are obtaining greater DNA characterization of the biofilm microbial communities in this process to better understand how we might be able to improve process performance. More specifically, we consider a zeolite-anammox system to remove ammonia and nitrate from secondary-treated wastewater at ambient temperatures (12 -30 °C). Until now, use of anammox bacteria has been largely limited to treatment of high-ammonia content wastewater at warm temperatures (30 -40 °C). Specifically, we investigate upscaling the zeolite-anammox system to nitrogen removal from relatively low-ammonia content (~35 NH3-N mg/L) effluent using gravity-fed 0.7 m wide and 0.17 m deep linear-channel reactors within pilot plants located at either the WWTP or some eight kilometers away. Following establishment, we monitored ammonia and nitrate concentrations along one reactor bi-weekly and only inflow -outflow concentrations at the other for more than a year. We found nearly complete ammonia removal within the first 22 m of reactor consistent with the theoretical 89% nitrogen removal capacity associated with the nitrogen-conversion stoichiometry of anammox bacteria. We also determined degradation parameters of a constant 1.41 mg NH3-N/L per hour in the first 15 m, or 20.7 g NH3-N/m3/day for overall reactor volume. At the higher flowrate of the second reactor, we achieved a removal rate of 42 g NH3-N/m3/day. Overall, the linear-channel reactors operated with minimal maintenance, no additional energy inputs (e.g. for aeration) and consistently achieved NH3-N discharge concentrations ~1 mg/L despite fluctuating temperatures and WWTP effluent concentrations of 20 -75 mg NH3-N/L. Further, we consider the upscaling of the zeolite-anammox process treatment to nitrogen removal from relatively high-ammonia content (~500 NH3-N mg/L) anaerobic-digester (AD) filtrate to facilitate reductions in WWTP nitrogen discharge. First, by operating a 210 L barrel reactor as a trickling filter with a 10% by volume initial bio-zeolite seeding fraction, we found that 6 -8 weeks elapsed before the anammox activity became apparent. Moreover, the 10-mm zeolite aggregate reactor achieved an 89% ammonia-N removal compared to the 85% achieved by the 20-mm aggregate. We then evaluated the performance of the trickling-filter design in a 68 m3 Baker tank nearly filled with 20-mm zeolite aggregate seeded with bio-zeolite at about 1.5% by volume. At an average inflow of 42 m3/day, about one year elapsed before achieving adequate anammox activity and acceptable treatment. Unfortunately, inadequate suspended solids pre-treatment of the AD filtrate resulted in clogging problems in the Baker tank reactor, so we evaluated aerobic-anaerobic cycling within the tank and then operated it (anaerobically) as a nitrate-scavenging tank. In the final anaerobic operational stage, nitrate effluent concentrations were <1 mg/L, perhaps due to dissimilatory nitrate reduction to ammonium by the anammox process, but ammonia removal fractions were only about 47%.

Publications

• Type: Journal Articles Status: Published Year Published: 2018 Citation: Collison, R.S. and M.E Grismer. 2018. Upscaling the Zeolite-Anammox Process: Treatment of secondary effluent. Water, 10(3):236. http://www.mdpi.com/2073-4441/10/3/236/pdf.
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Collison, R.S. and M.E Grismer. 2018. Upscaling the Zeolite-Anammox Process: Treatment of high-strength anaerobic digester filtrate. Water 10(11):1553. https://doi.org/10.3390/w10111553.
• Type: Journal Articles Status: Awaiting Publication Year Published: 2019 Citation: Zikalala, P., I. Kisekka, and M.E. Grismer. 2018. Calibration and global sensitivity analysis for a salinity model used in evaluating fields irrigated with treated wastewater in the Salinas Valley. Agriculture - in-press.
• Type: Conference Papers and Presentations Status: Awaiting Publication Year Published: 2019 Citation: Grismer, M.E. and P.G. Zikalala. 2018. Recycled water use, water demand and infrastructure in the Salinas Valley, CA. ASA Conference Proc.- in-press.

Progress 10/01/16 to 09/30/17

Outputs
Target Audience:Our target audiences are largely environmental groups, regulatory and resource agencies and cooperating Wastewater Treatment Plants (WWTPs); in particular we are working with the Monterey Recycled Water Agency in Salinas related to our agricultural water quality impacts assessments and with various Easy San Francisco Bay WWTPs with respect to developing low-cost wastewater treatment strategies directed at increasing water re-use capacity. Changes/Problems:Several do not accept that the zeolite-anammox treatment process is actually associated with anammox bacteria so we are obtaining additional DNA analyses of zeolite biofilms. In the Salinas Valley, some data collection continues to be challenging as well due to limited access either physically or politically; we are working with cooperators wherever possible. What opportunities for training and professional development has the project provided?We currently have two PhD candidates working on these projects. How have the results been disseminated to communities of interest?We have presented results to the WWTP staff and made a preliminary presentation to the Monterey Recycled Water Agency staff as we further develop this project. The primary work has been submitted for publication as noted above. What do you plan to do during the next reporting period to accomplish the goals?We plan to continue our assessments of the zeolite-anammox treatment process at cooperating WWTPs and are working on a long-term evaluation of agricultural development and water policies in the Salinas Valley during the past century to better inform practices and policies into the future anticipating changing climates conditions.

Impacts
What was accomplished under these goals? Water quality in San Francisco Bay is reportedly adversely affected by nitrogen loading from the wastewater treatment plants (WWTPs) discharging around the periphery of the Bay. Here, we consider use of zeolite-anammox systems to remove ammonia and nitrate from secondary-treated wastewater at ambient temperatures (12-30 C) as well as high ammonia content anaerobic digester filtrate at different WWTPs. Until now, use of anammox bacteria has been largely limited to treatment of high-ammonia content wastewater at warm temperatures (30-40 C). Specifically, we investigate upscaling the zeolite-anammox system to nitrogen removal from relatively low-ammonia content (~35 NH3-N mg/L) effluent using gravity-fed 0.7 m wide and 0.17 m deep linear-channel reactors within pilot plants located at either the WWTP or some 8 km away. Following establishment, we monitored ammonia and nitrate concentrations along one reactor bi-weekly and only inflow-outflow concentrations at the other for more than a year. We found nearly complete ammonia removal within the first 22 m of reactor consistent with the theoretical 89% nitrogen removal capacity associated with the nitrogen-conversion stoichiometry of anammox bacteria. We also determined degradation parameters of a constant 1.41 mg NH3-N/L per hour in the first 15 m, or 20.7 g NH3-N/m3/day for overall reactor volume. At the higher flowrate of the second reactor, we achieved a removal rate of 42 g NH3-N/m3/day. Overall, the linear-channel reactors operated with minimal maintenance, no additional energy inputs (e.g. for aeration) and consistently achieved NH3-N discharge concentrations ~1 mg/L despite fluctuating temperatures and WWTP effluent concentrations of 20-75 mg NH3-N/L. Treating the high-ammonia content (~500 NH3-N mg/L) anaerobic-digester (AD) filtrate will facilitate reductions in WWTP nitrogen discharge. First, operating a 210 L barrel reactor as a trickling filter with a 10% by volume initial bio-zeolite seeding fraction, we found that 6-8 weeks elapsed before anammox activity became apparent. Moreover, the 10-mm zeolite aggregate reactor achieved 89% as compared to 85% ammonia-N removal by the 20 mm aggregate. We then evaluated performance of the trickling-filter design in a 68 m3 Baker tank nearly filled with 20-mm zeolite aggregate seeded with bio-zeolite at about 1.5% by volume. At an average inflow of 42 m3/day, about one year elapsed before achieving adequate anammox activity and acceptable treatment. Unfortunately, inadequate suspended solids pre-treatment of the AD filtrate resulted in clogging problems in the Baker tank reactor, so we evaluated aerobic-anaerobic cycling within the tank and then operated it (anaerobically) as a nitrate scavenging tank. In the final anaerobic operational stage, nitrate effluent concentrations were <1 mg/L likely due to dissimilatory nitrate reduction to ammonium by the anammox bacteria, but ammonia removal fractions were only about 47%. Beneficial use of treated, or recycled wastewater is increasing in California, especially that used in irrigated agriculture. As growers in the northern Salinas Valley have been using recycled water since 1998, a significant concern remains about rootzone soil salinity accumulation, and salt loading to groundwater and surface water resources. Accumulation of rootzone and groundwater salinity is a primary concern associated with regular use of reclaimed water. We use data from a long-term field experiment (2000 to 2013) considering application of a range of blended fractions of recycled water and groundwater on different field crops using surface and pressurized irrigation systems to calibrate a rootzone salinity model to then evaluate accumulation trend and distribution of soil salinity across a 91.4 cm soil profile. The model results are used to describe the long-term salt transport and transformation in the soil accounting for meteorological daily records, crop evapotranspiration (ET), soil textural parameters, crop type, irrigation system and irrigation water quality. As with many distributed hydrologic models, model application requires determination of several input parameters that have varying levels of uncertainty. Two techniques were used to guide model parameter estimation, relative sensitivity and eventually validation of the salinity model. First, the Method of Morris, or Elementary Effect test is used to identify the input factors that have negligible influence on the output. Subsequently, a more time-consuming variance based method of Sobol' was used for factor fixing. Of the 33 parameters requiring specification, the sensitivity analysis indicated that only 7 were critical to the model output results and these were used for model calibration and validation. While model simulations successfully captured long-term trends in soil salinity, model predictions underestimated soil water electric conductivity (ECsw) for high ECsw samples. The model prediction error for the validation case ranged from 2.6% to 39%. Model fitting is improved by accounting for chemical addition to the soil as well as plant uptake of fertilizer and solutes. Salinity addition associated with fertilizer application add to prediction problems over time. As well, the complex spatial variability in the salinity field resulting from localized leaching in drip-irrigated fields contributes to modeling error. Application of the global sensitivity analysis with this model indicates that this method will help with field application and adoption of this salinity model within water management planning. Calibration and validation results also suggest that this approach could to evaluate long-term salinity trends and reference, or benchmark salinities for fields managed with treated wastewater to preserve soil health accounting for the seasonal, annual and decadal hydrology of the region. Next, we use the previously developed model to benchmark effects of recycled wastewater irrigation practices on the long-term dynamics of average seasonal root zone salinity (ECeS), drainage salt load (Sd) and surface runoff salt load (Sr). Simulation scenarios are based on cropping patterns over 13-years from 2000 to 2012 at the six field sites in Castroville in the Salinas Valley considered previously. The numerical simulation of long-term field scale variably saturated subsurface flow and transport is conducted using a modified, calibrated Isidoro & Grattan salinity model validated for the study area. This one-dimensional flow and transport model describes the long-term salt transport and transformation in the soil accounting for meteorological daily records, crop evapotranspiration (ETc), soil textural parameters, crop type, types of irrigation, irrigation water quality and capillary rise from shallow groundwater. Model simulations included determination of benchmark scenarios for fields irrigated with a range of recycled- and ground-water blends. Simulation results show that the seasonal root zone salinity remains below stress thresholds for all crops grown in this region including relatively salt-sensitive crops. Rainfall and applied water EC predominantly effect the accumulation of salts in the root zone profile, however, for two sites the types of crops selected (thus ETc) had a significant effect on soil EC. Annual runoff salt load was an order-of-magnitude greater than drainage salt load. Cumulative salt loads as drainage ranged from 0 to 368 kg/ha and those as runoff ranged from 2,834 to 8,068 kg/ha. Of the crops in the area (artichokes, broccoli, cauliflower, lettuce and strawberries), artichoke cropping results in the least salt loading. This study concludes that the potential for the salinization of the Salinas River from surface salinity accumulated in field runoff at the end of the growing season is an important threat in fields irrigated with saline waters, especially for fields irrigated with drip and/or sprinkler systems.

Publications

• Type: Journal Articles Status: Published Year Published: 2017 Citation: Grismer, M.E. and R. S. Collison. 2017. The Zeolite-Anammox Treatment Process for Nitrogen Removal from Wastewater --A Review. Water, 9(11), 901; doi:10.3390/w9110901
• Type: Journal Articles Status: Under Review Year Published: 2018 Citation: Collison, R.S. and M.E. Grismer. 2018. Upscaling the Zeolite-Anammox process: Treatment of secondary effluent. Water.
• Type: Journal Articles Status: Under Review Year Published: 2018 Citation: Collison, R.S. and M.E. Grismer. 2018. Upscaling the Zeolite-Anammox process: Treatment of high-strength anaerobic digester filtrate. Water.

Progress 10/01/15 to 09/30/16

Outputs
Target Audience:Our target audiences include local water agencies and resource conservations districts as well as environmental groups, and state regulatory agencies. To that end, we have made a couple presentations about this work at local conferences as well as publishing in local and national periodicals. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Two PhD candidates completed their Qualifying Exams and are working on aspects of this project. How have the results been disseminated to communities of interest?We have contacted the Water Agency partners and are in the midst of the lab and field research this past year, though we completed one more related Drought tip that was recently published What do you plan to do during the next reporting period to accomplish the goals?Work is underway by both PhD students to complete the soil-water modeling effort and to characterize the properties of biochars developed from two different agricultural waste streams under different formation conditions. Similarly, we are preparing papers from our WWTP work on the zeolite-anammox process and considering its use in possible constructed wetland treatment with direct discharge to the Bay area estuaries.

Impacts
What was accomplished under these goals? We focused on the first two objectives of this project during this period, the first considering "physical factors affecting water use" and the second considering developing "methods to address emerging water management issues". By combining field measurements of rootzone leaching and soil-water computer modeling, we expect to develop the practical knowledge necessary for growers in the Monterey region and elsewhere across the state to determine acceptable applied water salinity levels associated with long-term recycled water use on soils and crop production. We are using preliminary information from long-term field studies underway (reported on previously) about acceptable levels of applied water salinity and minimum rainfall needed to help determine whether or not continued use of the recycled water, or salt-affected groundwater for irrigation over the decadal time period is acceptable. We are currently preparing the soil-water modeling needed to describe the changes in soil-salinity, the leaching fractions to groundwater associated with rainfall, rainfall plus irrigation and irrigation alone for a range of recycled water blends. This modeling effort will be used in conjunction with the field studies to help guide water agency managers and growers in the use of recycled waters for irrigation. Our work towards the second objective centers on two different approaches towards water conservation and development of recycled water resources. The first approach is considering development of biochar soil amendment strategies directed at increasing soil -water holding capabilities as well as nutrient (e.g. nitrate) retention in soils, thereby decreasing leaching. This idea was derived from terra preta de indio soils within the Amazonian rainforest where soils were anthropogenically altered for crop production by the successive incorporation of charred remains in soils. However, biochars can be produced from several different feedstocks, processes and formation maximum temperatures that all presumably affect their characteristics for use as a soil amendment. Thus, few recommendations are available describing the desirable biochar properties and the biochar application rates and period of application appropriate for different soils to achieve the desired effects. Thus far, the primary interest in biochar has been as possible carbon sequestration tool within soils. This research seeks to understand the sustained effect of biochars on the water and nutrient retention properties of various textured soils in both field agricultural and for nursery or hydroponic systems. The second approach to the project second objective is to develop greater nitrogen removal efficiencies at wastewater treatment plants (WWTPs) to improve recycled water quality for possible direct discharge to estuaries, or use as irrigation to be part of a broader water management strategy for the region. Previously, we developed a zeolite-anammox process to remove nitrogen species in small constructed wetland systems and are now upscaling that effort to regional WWTP application. The zeolite-anammox process uses zeolite to provide the media for a fixed film reactor. The zeolite particles can be sized to accommodate biofilm growth and provide a long-lived system that is not prone to clogging. The first stage was the pilot plant project using six 55-gallon drum reactors to test different methods of aeration and different sizes of zeolite media using actual WWTP anaerobic digester discharge. The second stage employed an intermediate-scale 20,000 gallon Baker tank that treated approximately 10% of the WWTP concentrate, or about 11,000 gallons per day of influent containing about 500 mg/L of ammonium. The Baker tank project included three stages of testing including (a) a preliminary establishment period, during which time anammox bacteria gradually colonized the whole tank, (b) a short-circuiting and flood/drain aeration phase, and (c) a partial media clogging of the aerated layer that included a greater anammox production period, with effluent nitrate concentrations less than 0.1mg/L. Our preliminary results released to the WWTP operated resulted in recognition by the California Water Environment Association with a Research Achievement Award.

Publications

• Type: Other Status: Published Year Published: 2016 Citation: Grismer, M.E. and D.L. Haver. 2016. Use of treated wastewater for crop productions. UC - ANR Drought Tip Publication 8534.

Progress 10/28/14 to 09/30/15

Outputs
Target Audience:Our target audiences include local water agencies and resource conservations districts as well as environmental groups, and state regulatory agencies. To that end, we have made a couple presentations about this work at local conferences as well as publishing in local and national periodicals. Changes/Problems:Though not surprised, the paucity of directly applicable data has been limiting towards coding the soil-water to groundwater interactions model that we currently envision. We have adapted the groundwater portion using a simplified methodology that requires only driller log information that Grismer developed earlier for the Antelope Valley of CA. We expect this modification in addition to simplifications of the soil-water model to help us develop the first generation of the overall model so as to enable development of the guidelines we anticipate creating. What opportunities for training and professional development has the project provided?Currently, one PhD student together with an undergraduate McNair Honors scholar are working on this project. The PhD student has completed her research proposal (January 2016) in anticipation of her Qualifying Exam in February 2016. She has also established relationships with a couple water districts with whom we hope to work more closely. How have the results been disseminated to communities of interest?In this first year, we are just setting up the modeling and basic information requirements and have submitted abstracts for presentations at conferences later in the spring of 2016. What do you plan to do during the next reporting period to accomplish the goals?We are planning to code these insights outlined above into a soil and groundwater impact model so as to better advise growers, water agencies and the public about appropriate use of recycled water for fruit and vegetable crop production and possible associated impacts on groundwater supplies. Later, we hope to establish pricing structures for the recycled water use that encourage its use rather than groundwater pumping that exacerbates sea-water intrusion problems in the regional aquifers.

Impacts
What was accomplished under these goals? We have focused on the first two objectives of this project during this period; the first considering "physical factors affecting water use" and the second considering developing "methods to address emerging water management issues". We expect to develop the practical knowledge necessary for growers in the Monterey region and elsewhere across the state to determine acceptable applied water salinity levels associated with long-term recycled water use on soils and crop production. Wehave developed preliminary information from field studies about acceptable levels of applied water salinity and minimum rainfall needed to help determine whether or not continued use of the recycled water, or salt-affected groundwater for irrigation over the decadal time period is acceptable. Through a combination of long-term field monitoring of soil salinity parameters subjected to irrigation using a range recycled water blends with groundwater, and soil-water modeling to determine the actual leaching fractions associated with rainfall, rainfall plus irrigation and irrigation alone, realistic insights will be obtained to guide recycled water managers and growers. These insights can be used to develop water pricing schemes that limit groundwater usage while providing an incentive for recycled water use in the broader region. Such an approach for the relatively salt-sensitive crops grown in the Monterey region should provide guidance elsewhere in the State and West as to the use of recycled water crop irrigation. Meanwhile, we also developed a simple, real-time field monitoring methodology to determine irrigation surface advance cut-off times directly for each irrigation.

Publications

• Type: Journal Articles Status: Published Year Published: 2014 Citation: Platts, B. and M.E. Grismer. 2014. Chloride levels increase after 13 years of recycled water use in the Salinas Valley. California Agriculture. 68(3): 68-74.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Platts, B. and M.E. Grismer. 2014. Rainfall leaching is critical for long-term use of recycled water in the Salinas Valley. California Agriculture. 68(3): 75-81.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Arnold, B.J., S. K. Upadhyaya, W. W. Wallender, and M. E. Grismer. 2014. Sensor-based cutoff strategy for border-check irrigated fields. ASCE J. Irrig. & Drainage Engr. 141(7), 04014081.
• Type: Other Status: Published Year Published: 2015 Citation: Grismer, M.E. 2015. Use of shallow groundwater for crop production. UC - ANR Drought Tip Publication 8521. June.
• Type: Other Status: Published Year Published: 2015 Citation: Grismer, M.E. and K.M. Bali. 2015. Use of saline drain water for crop productions. UC - ANR Drought Tip Publication 8554. October