MBR vs SBR for Ammonia Removal in High Strength Wastestreams

Several considerations enter into determining whether a Membrane Bioreactor or Sequencing Batch Reactor is more suitable for nitrification of a high strength wastewater. Landfill leachate is a very common high strength wastewater found throughout the US and across the globe that is comparable to many industrial wastes. High COD, extremely high ammonia levels, and significant total dissolved solids (TDS) concentrations are seen at many landfills. Traditionally in most of the US, these wastes have been hauled or pumped to POTWs for disposal. Permit nutrient limitations on POTW discharges have tightened, requiring many landfills to employ pretreatment for indirect discharge or secondary treatment (or more) for direct discharge. The selection of the proper treatment technology for these types of wastestreams requires careful consideration.In the past decade or two, Sequencing Batch Reactors (SBRs) and Membrane Bioreactors (MBRs) have become popular activated sludge technologies. When applied to treating unusual strength wastewaters like leachates, the strengths and weaknesses of these treatment approaches provide opportunities for designers. SBRs are simpler and have a longer track record, but MBRs provide an answer to sludge quality and biomass inventory issues that often arise.This paper presents some of the key considerations and lessons learned from designing and operating single-sludge systems that nitrify high strength wastes based on more than a decade of experience with numerous landfill leachates. This experience nitrifying leachates can be applied to other high strength wastewaters just as experience nitrifying high strength industrial wastewaters can be applied to leachates.