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Investigating the Feasibility of a Membrane Biofilm Reactor to Achieve Low Nitrogen Levels for Water Reclamation and Reuse

Project: 06-13
Year Released: 2012
Type: Scientific Investigation

Program: Principal
Funding Partners: Bureau of Reclamation, California State Water Resources Control Board
Total Investment: $151,180.88 (Cash)

Principal Investigator: R. Shane Trussell, Trussell Technologies, Inc.

Background

In an effort to satisfy growing water demand in the face of dwindling water resources, many communities throughout the U.S. and the world are turning to water reclamation and reuse. Recycled water is a renewable and drought-proof resource whose availability increases proportionally with increases in potable water use. Recycling water captures a valuable source of water that is increasing with population growth and supplements conventional water supplies. Recycled water is increasingly the most cost-effective means of increasing a municipality’s water portfolio.

Secondary effluent generated by wastewater treatment plants, typically, comprises relatively low COD and TSS content and moderate nutrient concentrations, which may still be too high for discharge to water bodies sensitive to eutrophication and nitrogen contamination. Therefore, there is much interest in implementing tertiary treatment of secondary effluents to produce recycled water with improved water quality that can be reused directly for irrigation and industrial purposes; or indirectly, following a period of storage in surface reservoirs or underground aquifers.

Goals and Objectives

The project explores methods to remove nitrate from secondary effluent to a low level (< 10 mg N/L) for water reclamation purposes using an innovative H2 fueled Membrane Biofilm Reactor (MBfR). This project will comprehensively investigate nitrate removal rate as a function of loading rate, hydraulic retention time, substrate (or H2) utilization rate, and membrane area. Employing a pilot-scale MBfR to treat secondary effluent will be instrumental in establishing the actual design criteria for full-scale facilities and will closely capture the operation and maintenance issues associated with full-scale operation.

Research Approach

This research report presents 9 months of results from the operation of two parallel membrane biofilm reactor (MBfR) pilot plants. The pilot plants were used to evaluate the MBfR’s ability to successfully denitrify a secondary effluent. This MBfR pilot study represents the first commercial application of this promising treatment process in an advanced wastewater treatment train.

Findings and Conclusions

In general, the MBfR process successfully denitrified wastewater to very low nitrate levels and often achieved undetectable concentrations, depending on operating conditions. In contrast to groundwater applications, the high microbial concentrations and wide diversity of microbes in the feed water resulted in an established biofilm process in a relatively short period of time (typically 10 to 14 days). This ability to establish an effective biofilm so quickly also means that following a shutdown or process interruption (i.e., lack of H2), the process is capable of resuming effective nitrate removal within a few days. If an extended shutdown is encountered, the process will re-establish effective nitrate removal in the same time frame as a start-up (10 to 14 days).

The MBfR process design continues to evolve and developments will further reduce treatment costs. It is important to note that the hydrogen market and future hydrogen costs will play a significant role in the overall cost effectiveness of this process.

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