Comparison of Two Membrane Bioreactors and an Activated Sludge Plant With Dual-Media Filtration: Nutrient and Priority Pollutents Removals

Abstract

Two pilot-scale MBR plants were operated at the Los Angeles County Sanitation Districts' Whittier Narrows Water Reclamation Plant (WNWRP) for over a year. The plants were manufactured by Kubota Corporation and Zenon Environmental Inc. The objective of this study was to compare the long-term performance of these systems, with respect to effluent water quality, to that of the WNWRP. Water quality parameters of particular interest were COD, suspended solids, turbidity, nitrogen, priority pollutants, indicator organisms, and N-nitrosodimethylamine (NDMA). Primary effluent from the plant was used as influent to the MBRs. Average COD, total suspended solids (TSS), and ammonia concentrations in the primary effluent were 330, 100, and 24 mg/L, respectively. Key findings from the study include (1) both MBR plants achieved excellent COD (>95%), TSS (> 99%), and turbidity (typical values <0.1 NTU) removals; (2) the Zenon plant was able to achieve excellent nitrogen removal with an average effluent nitrate nitrogen concentration of 5.4 mg N/L and an ammonia nitrogen concentration typically <1 mg N/L; (3) all priority pollutants detected in the primary effluent were removed by the MBRs to levels below the detection limits or to levels equivalent to that of the WNWRP effluent; (4) both MBRs achieved >6-log removal of total coliform and fecal coliform, and >5-log removal of indigenous coliphage; (5) the median NDMA concentration of raw wastewater was 100 ng/L. This concentration was reduced by approximately 80% by the primary sedimentation and biological treatment processes of the WNWRP and Zenon MBR.

Ultrafiltration (UF) Pilot Plant for Municipal Wastewater Reuse in Agriculture: Impact of the Operation Mode on Process Performance

“…Interest in the use of UltraFiltration (UF) membrane processes as an alternative technology to conventional disinfection techniques, designed to achieve the restrictive agriculture wastewater reuse standards, is growing [1][2][3]. To this aim, the application of UF membrane processes has proved to be competitively priced and the possibility of easily installing the UF equipment into the current wastewater treatment facilities is a further key element [4,5].…”

Chlorination Disinfection Requirements for Membrane Bioreactor Permeate

“…In case of a membrane failure, bacteria will break through the process and have to be disinfected. The addition of ML to permeate resulted in total coliform bacteria presence in the mixture and allowed the inactivation of total coliform by free chlorine to be evaluated; total coliform levels in MBR permeate are typically very low or below detection (Mansell et al, 2004). The samples of permeate and/or permeate blended with ML were first analyzed for general water quality parameters including pH, turbidity, total suspended solids (TSS), nitrogen species, chemical oxygen demand (COD), total coliform, and chlorine demand.…”

“…As a result, the MBR process produces permeate with significantly better water quality, with respect to particulate matter and microbial indicators, than effluents from conventional tertiary treatment processes (Mansell et al, 2004). Despite the improved water quality, disinfection of permeate is required for reuse applications to ensure protection of public health.…”

Ex situ treatment of N-nitrosodimethylamine (NDMA) in groundwater using a fluidized bed reactor

“…This system, which utilizes a membrane system to supply hydrogen gas to a suspended growth reactor, was found to reduce influent NDMA concentrations from 800 ng/L to 18 AE 6 ng/L (w97.7% efficiency), which is the most effective design reported to date other than the propane-fed MBR (Hatzinger et al, 2011). NDMA removal by biological means has also been examined at a number of different wastewater treatment plants (WWTP) (Sedlak et al, 2005;Krauss et al, 2009), in MBRs used to treat effluent from those plants (Mansell et al, 2004(Mansell et al, , 2005, and in various processes used in water reclamation plants . The efficiency of these different systems for NDMA removal is highly variable.…”

“…Moreover, NDMA removal in individual plants was inconsistent, ranging from 18% to 96% at a facility in Switzerland (Krauss et al, 2009), and 0% to 75% at a U.S. WWTP (Sedlak et al, 2005). Removal in the MBR systems treating WWTP effluent, which had an average influent concentration of w100 ng/L averaged 80% (Mansell et al, 2004), and an average of 70% removal was observed during the biological treatment phase at a wastewater reclamation plant in Los Angeles County, CA from 80 ng/L to 26 ng/L .…”