NEW NITRIFIER BIOAUGMENTATION PROCESS CONFIGURATION TO ACHIEVE YEAR ROUND NITRIFICATION AT LOW SRTs
Abstract:This paper presents a new process configuration, which is based on the concept of nitrifier bioaugmentation (or seeding), that allows complete nitrification to be achieved at low solids retention times (SRTs) on a year round basis for plants that have a minimum of two activated sludge treatment trains. The new process couples a membrane bioreactor system as the second stage to a non-nitrifying activated sludge system. The membrane bioreactor is used to optimize the growth of these autotrophs by achieving complete nitrification of ammonia derived from the influent wastewater and the anaerobic digester recycle stream. The mixed liquor of the membrane bioreactor, containing an enriched culture of nitrifying bacteria is used as the augmentation source for the remainder of the plant. To allow the other treatment train(s) to nitrify, the waste sludge from the membrane bioreactor is directed or “donated” to the “Receiver” plant(s). Steady-state and dynamic simulations are performed to allow comparison of this new process configuration to a traditional nitrification upgrade, as well as an upgrade based upon the process reported in Kos (1998). Modelling results indicate that the new process is generally more robust in terms of nitrification performance during dynamic flow and loading situations. Based on the design criteria and operation conditions presented in this paper, a nitrification upgrade with the new bioaugmentation process would require 23 and 26 percent of the tankage than a comparable traditional nitrification upgrade and an upgrade based on the process described in Kos (1998), respectively. Further investigative work is required to determine the flux that could be achieved in the bioaugmentation membrane bioreactor system, which would operate on secondary effluent at relatively low solids concentrations (i.e. ∼1,500 mg/L).
Document Type: Research Article
Publication date: January 1, 2001
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