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Report sorted into three groups: established systems (proven and in practice), emerging systems (partially proven, limited full- scale application), and innovative concepts (new ideas that show promise). Key treatment technologies from the emerg- ing treatment systems category recommended to be carried forward for Phase II research included: anaerobic MBR and full-stream anammox process. A few other processes were also recommended for testing. These processes are: next step for the anaerobic MBR is to build on this research by designing and operating a larger-scale system to analyze the ability to meet stringent reclaimed water standards with subsequent disinfection. This larger system would be fully automated and use full-scale components. Full-Stream Anammox Figure 2. Planning-level comparison of energy use for UV disinfection compared to hypochlorite generation (Kansas City 2008, Dallas Water Utilities 2010). [Note: This is a comparative figure only, as disinfection for these projects were not to reuse standards.] Anaerobic MBR The anaerobic MBR has now been proven as an effective treatment process by different research groups and with variations of the MBR technology. Kim et al. (2011) used a fluidized bed MBR with GAC to produce a high quality effluent (5 mg/L BOD and zero TSS) with minimal membrane fouling. The same research estimated a decrease in second- ary process energy use of ~50% and estimated an increase of methane production of 75%. While promising, this research was done on a very small scale, in a warm climate, used syn- thetic wastewater, and did not address long-term membrane fouling concerns. Researchers at the University of Michigan12 have been con- ducting anaerobic MBR research with the testing of a small- scale reactor (5L) on both synthetic wastewater and munici- pal wastewater at temperatures as low as 15°C. This work was done without the GAC scour- ing, instead relying upon biogas sparg- ing to minimize membrane fouling. For the municipal wastewater work, effluent BOD of less than 30 mg/L was achieved for extended periods of time. Treatment Level Activated Sludge Activated Sludge With Nitrifi cation MBR With Nitrifi cation The proposed 24 Water Online The Magazine, Wastewater Edition ■ wateronline.com Energy (kW-hrs/1,000 gallons) UV Secondary Process -0.50 -0.90 -1.20 Energy Recovery +0.72 +0.65 +0.60 -0.50 -0.26 -0.21 Table 1. Approximate energy use/energy generation for select processes at a WWTP when treating a flow of 12-15 mgd. [Notes: Energy use for UV is reduced compared to other secondary processes due to increase water quality and reduced regulated dose. Secondary Process: Energy values are strongly correlated to process SRT, aeration efficiency, and nutrient removal. Energy Recovery: Not normally done for plants smaller than 8-10 mgd because of economic considerations. The different energy recoveries shown for the listed treatment levels are due to different biodegradable fractions of the waste activated sludge resulting from different sludge ages. The anammox process is applied as a side-stream treatment system on digested sludge returns or waste streams with high ammonia and low carbon contents3. Since the anammox pro- cess requires approximately equal parts of ammonium and nitrite, it is often implemented as a nitritation-anammox, or deammonification, process in series to accumulate nitrite for use by the anammox bacteria as the electron acceptor3. If the anammox is preceded by nitrification, only part of the ammo- nia needs to be nitrified to nitrite, which helps to reduce cost compared to nitrifying all of the ammonia6. There are advantages to using the anammox process over conventional nitrification-denitrification processes for removal of nitrogen from high ammonium content waste streams. For one, nitritation-anammox requires 57% less oxygen and 86% less carbon than conventional nitrification-denitrification. In addition, it is completely autotrophic so nutrients and trace elements are not required. The low biomass yield means low sludge production. External carbon addition is not required and methanol is even toxic to the anammox bacteria. Energy costs are also low because oxygen is not required for the anammox process and only limited oxygen is required for the partial nitritation3, i.e., aeration is not required. The anam- mox process also has disadvantages. A pre-partial nitritation is required for converting part of the ammonia stream into nitrite prior to the anammox process1. Anammox bacteria also have a slow growth rate with a doubling time of 11 days at 32-33°C9. This has the benefit of a low biomass yield but requires efficient sludge retention (long SRT) and means long start-up times to get sufficient biomass concentrations4. Conditions for anammox accumulation include long SRTs, stable operation, presence of nitrite, lack of oxygen, and lack of donors causing denitrification of nitrite8. The competition between anammox bacteria and other denitrifiers makes the start-up process difficult because denitrification is a faster pro- cess. This becomes a bigger problem when carbon is present1. The predominant application for anam- mox processes has been for treatment of digester reject water or industrial anaerobic wastewater treatment in streams that have limited organic carbon content13. However, the application could