Technology Review of BAT for Removal of Nitrate in Drinking Water

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1 Technology Review of BAT for Removal of Nitrate in Drinking Water The information for this technology review was obtained from the following sources: Section , Title 18, Chapter 4 Ariz. Admin. Code ADEQ s Safe Drinking Water Regulations Water and Wastewater Engineering Design and Principals Professional Edition by Davis, M. Use of agricultural waste for the removal of nitrate nitrogen from aqueous medium Mass Transfer Modeling of Nitrate in an Ion Exchange Selective Resin Kinetic modelling of the retention of nitrates by Amberlite IRA Introduction The purpose of this technology review is to evaluate the Federal and State recommended Safe Drinking Water Regulations (SDWR) Best Available Technologies (BAT) for removal of nitrate in drinking water. The state recommendations will be from Arizona, California, and Nebraska, Departments of Environmental Qualify. BAT means the best technology, treatment techniques, or other means which the regulatory Administration finds, after examination of efficacy under field conditions and not solely under laboratory conditions that are available ("Title 18, chapter," 2008, Page 12). The BATs from the State and Federal Administration will be evaluated using a decision matrix. The constraints used in the decision matrix will be generated to reflect the needs of a small farming community affected by groundwater contaminated with nitrate. The household(s) in the small farming community get there drinking water from a shallow groundwater aquifer and is delivered via a well. The shallow ground water aquifer happens to be contaminated with nitrate. 1.1 Source Description A small community (1 5 households) is one of the many that obtains drinking water from a well. The well is tapping into one of the many aquifers contaminated with nitrate due to fertilizing crops or raising livestock. Table 1 below shows the results from the Current Conditions report whose purpose is to identify common groundwater constituents and co contaminants in areas with aquifers contaminated with nitrate. The small community is assumed to have a water delivery system with 500 gallons of water storage and 75 PSI water pressure per house. The water storage tank is located in a shed that has roughly 64 cubic feet of available space for a new water treatment system to remove nitrate from water. 1.2 BAT Requirements The project will be successful if the selected BAT meets nitrate removal project criteria and constraints. Criteria:

2 Remove Nitrate to Safe Drinking Water Standards (SDWS) Constraints: Must fit in a 4 by 8 by 2 high area per household Must process 0.2 gallons per second of raw drinking water per household Must be capable of a target nitrate concentration of 2 mg/l as nitrogen Must be able to scale design for a service load of 1 to 5 households Must be cost effective due to limited economic support for private water treatment Must require no electricity 2.0 BAT Engineering Analysis The BAT s recommendations from the EPA, Arizona Department of Environmental Quality (ADEQ), and California Department of Environmental Quality (CDEQ) with respect to SDWS for nitrate are considered below. Nitrate removal recommendations from Water and Wastewater Engineering by Mekenzy L. Davis will be used for comparison to State and Federal regulations. The BATs from the 4 government sources point to the same technologies. Table 2 below shows the Best Available Technologies by source. Table 1: BAT Summary Source of BAT BAT option 1 BAT option 2 BAT option 3 EPA Ion Exchange Reverse Osmosis ADEQ Ion Exchange Reverse Osmosis Electrodialysis CDEQ Ion Exchange Reverse Osmosis Electrodialysis Davis Ion Exchange Reverse Osmosis Biological Denitrification 2.1 Identification of Alternative Nitrate Controls The 4 Administrations in the BAT Summary table recommend Ion Exchange, Reverse Osmosis, and Electrodialysis for removal of nitrate from drinking water. Mekenzy L. Davis also recommends Biological Denitrification but due to the small scale of this project, biological denifrication will not be considered. The three technologies will be evaluated with respect to the project evaluation criteria. Evaluation criteria have been generated to be used in the evaluation of the alternative nitrate controls. Each of the alternative controls will be rated with respect to the evaluation criteria from 1 to 5 (1 being low and 5 being high). Evaluation Criteria: Size, the nitrate removal system will have to fit into a somewhat small shed. A score of 1 in this field means that the technology will not fit in the allotted space. A score of 5 in this field means the design will easily fit in the allotted space. Cost, The operation cost and the initial investment cost will be important because the small farming community is expected to have limited economic support. A score of 1 means that that the operation/installation cost of the technology is relatively high with respect to the other technologies being evaluated. A score of 5 means that the

3 operational/installation cost is relatively high with respect to the other technologies being evaluated. Waste Stream, it is important to have a waste stream that is easily managed. A score of 1 in this evaluation criteria means the waste stream generated by the technology will be hard to dispose of. A score of 5 means the waste stream is easily disposed of. Complexity, the complexity of the technology will be evaluated to required time necessary to evaluate technology in the lab. A technology will receive a score estimate of 1 if that technology is very complex and requires hard to use equipment to analyze. A technology will receive a score estimate of 5 if that technology is simple and requires relatively simple equipment to analyze. Resource Demand, the amount of resources (electricity or other) required to operate the technology will be estimated. A score of 1 will reflect a system that uses a lot of resources to operate. A score of 5 will reflect a system that requires very few resources to operate. Efficiency, the efficiency of the system will be considered to be the resource demand in kilograms per nitrate as nitrogen removed in kilograms. A score of 1 means that the efficiency as stated above is relatively high when compared to the other technologies. A score of 5 means that the efficiency is relatively low when compared to the other technologies Ion Exchange Ion Exchange is a reversible reaction in which a charge ion (nitrate in our case) in solution is exchange for a similarly charged ion. The charged ion in solution will then be stuck to an immobile solid particle called a resin. Ion exchange is generally used for water softening but can be used to remove salts like nitrate. Ion exchange technology is used in individual homes and wastewater treatment plants (Davis, P. 333, 2011). All of the Administrations recommend ion exchange for removing nitrate from drinking water. Add stuff about study Membrane Filtration Reverse Osmosis and electrodialisis are membrane processes that use the difference of the permeability of water constituents as a separation technique. In reverse osmosis the water migrates across the membrane due to a concentration gradient generated by a power supply leaving a concentrated form of the contamination on one side and clean water the other side. In electodialis an electrical current is used in conjunction with a membrane to desalinated water by separating the ions in the water. The process produces a desalinated water stream and a concentrated salt waste stream. In our case the concentrated salt stream would be nitrate (Davis, P. 369, 2011). Figure x below shows a sample process diagram of reverse osmosis.

4 Figure 1: Reverse Osmosis Schematic (Davis, P.371, 2011) Add stuff about a study Biological Denitrification Denitrification consists of a sequence of enzymatic reactions leading to the evolution of nitrogen gas. Biological denitrification occurs naturally when certain bacteria uses nitrate as there terminal electron acceptor in the repertory system in the absence of oxygen (SOARES, P. 2, 2000). The process involves the formation of a few nitrogen intermediates presented below. Treatment of the water can take place in the aquifer or above ground in large reactors. The denitrifying bacteria require suitable carbon and energy source to thrive. The bacteria may be difficult to stabilize. 2.2 Evaluation of Alternative Nitrate Controls Table 2: Decision Matrix of Nitrate Controls Technology Ion Exchange Membrane Filtration Biological Denitrification Size Cost Waste Stream Complexity Resource Demand Efficiency Totals:

5 3.0 BAT Recommendation Basic Requirements for Ion Exchange to work: Strongly Basic Nitrate Selective Anion Exchange Resin like IND NSSR. The fixing of nitrates could be best described by the pseudo second order and the intraparticle diffusion models. Amberlite IRA 410 is specifically suited for use in two column water demineralization

6 Reference List cdn.com/s /1 s2.0 S main.pdf?_tid=56cd595c 196e 11e aab0f01&acdnat= _081297c25b59fb86093c98257fb634c5 Arizona Department of Environmental Quality, (2008). Title 18, chapter 4, ariz. admin. code adeq's safe drinking water regulations. Retrieved from website: Code of federal Regulations, (2004). 40 cfr variances and exemptions from the maximum contaminant levels for organic and inorganic chemicals.. Retrieved from Legal Information Institute website: California Code of Regulations, (2013). California regulations related to drinking water. Retrieved from California Department of Public Health website: pdf Davis, M. (2011). Water and wastewater engineering. McGraw Hill Professional. SOARES, M. I. M. (2000). Biological denitrification of groundwater. Kluwer Academic Publishers, 123, Retrieved from