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Non-Fouling Water Reuse Technologies


OBJECTIVE: Develop a non-fouling water reuse technology to achieve field-potable water quality from gray water influent. DESCRIPTION: Supply of water for potable and non-potable uses at contingency operating bases (COBs) represents a significant logistical and economic burden for the Army. To help alleviate this burden, on-site water treatment with reverse osmosis (RO) membrane technology has been applied for tactical water production and more recently for water reuse. Benefits of RO membrane technology include its ability to remove a wide variety of contaminants and drastically reduce total dissolved solids (i.e., salts) in a single treatment step. However, RO membrane technology is susceptible to foulants that decrease water production and energy efficiency. As a result, pretreatment systems such as conventional treatment processes (coagulation, flocculation, sedimentation, and filtration) or low-pressure membrane filtration (microfiltration, ultrafiltration) are required. While generally effective when applied with careful operator attention, these processes are not ideally suited for the variability in influent water quality and operational schedule in contingency operating environments. Many of the systems also require routine maintenance, such as cleaning of foulants from membranes, and replacement of critical system components, which represents additional operational burden. To support the Army"s goal of reducing water demand at contingency operating bases (COBs) by 75%, under Science & Technology Challenge Area 4a, SBIR proposals are sought that will further improve water reuse capabilities at COBs. Specifically, the development of water reuse technology that is not susceptible to performance degradation due to fouling, regardless of influent water quality or system operation schedule, is desired. Innovative systems that use alternative approaches to reverse osmosis technology but still produce the same quality of product water are of interest. Systems should not require extensive pretreatment (beyond roughing filtration), nor should they require extensive post-treatment (beyond granular activated carbon polishing and chlorination). Systems should be designed and tested against the following metrics: 1) Ability to produce field potable quality water from gray water sources. 2) Ability to produce water with less than 500 mg/L total dissolved solids. 3) Non-fouling (operator-mediated cleaning frequency greater than monthly, and no need for replacement of components due to fouling). 4) Autonomous operation. 5) Maintenance requirement of less than 30 min/week. 6) Energy consumption less than 20 kWh/kgal product water. 7) Water recovery of 90% or more. 8) Physical footprint of less than 1 cubic meter per 1 kgal/day product water. While the intended reuse application would likely not be human consumption, potable water quality levels are still desirable for other human-contact reuse applications such as showering. Current Army field policy allows for the recycling of gray water from laundry and shower facilities for shower use.1 PHASE I: Phase I should include a bench scale demonstration of the water treatment performance and a detailed engineering estimate of the energy efficiency, maintenance requirements, and physical footprint at design scales. Water treatment performance testing shall be performed over a period of at least 3 months in a manner consistent with published gray water treatment testing standards.2 Challenge water formulations shall be designed using a standard base formulation and augmented to reflect water quality conditions expected in contingency operating environments. Engineering estimates of energy efficiency, maintenance requirements, and physical footprint shall be made for design case of 10 and 20 kgal/day. Phase I metrics shall include: 1) Demonstration of sodium chloride removal efficiency>99% 2) Demonstration of BOD reduction to levels below 10 mg/L 3) Demonstration of total coliform bacteria removal to 0 cfu/100 ml 4) Projected energy efficiency of<20 kWh/kgal at 10 kgal/day design scale 5) Projected footprint of less than 10 cubic meters at 10 kgal/day design scale PHASE II: Phase II should include design, assembly, and testing of a 1 kgal/day system. The first year should focus on design and assembly of the prototype. Designs shall be fully drafted using professional grade drafting software, with all parts specified in terms of size, material, and source. Systems shall be assembled and flow tested using clean water by the end of the first year of Phase II funding. The second year of Phase II should focus on testing the system at 1 kgal/day in a simulated relevant environment. Systems should be tested over a 6-month period using a test protocol consistent with the NSF 350 testing standard.2 Challenge water formulations and system operation schedule shall be representative of contingency operating environments. Water treatment performance, energy consumption, and maintenance requirements shall be documented in detail. Phase II products shall include: 1) A water purification system that is less than 10 cubic meters in size and produces 10 kgal/day, along with detailed specifications and drawings 2) A report detailing water treatment performance, energy consumption, and maintenance requirements over a 6-month test period Phase II metrics include: 1) Demonstration of maintenance intervals of at least one week and less than 30 minutes in duration (each). 2) Demonstration of sodium chloride removal efficiency>99%, BOD reduction to levels below 10 mg/L, and total coliform removal/inactivation to less than 2 cfu/100 ml. 3) Demonstration of energy efficiency of<20 kWh/kgal. PHASE III: Military applications for a system that meets the metrics described herein may include water reuse in contingency operating environments; water reclamation at installations; distributed water reuse systems at installations; and aquifer recharge at installations. Additional commercial markets may include: household water purification and reuse systems; municipal water and wastewater treatment; recovery of water during oil and gas production operations, such as fracking; and industrial water treatment. REFERENCES: 1) U.S. Army Public Health Command (formerly USACHPPM). Non-potable Water Substitution and Reuse in the Field. TIP NO. 32-002-0111. December 2008. Available online at: 2) National Sanitation Foundation. Onsite Residential and Commercial Reuse Treatment Systems. July 2012.
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