Innovative Process Modifications Resolve Consent Order and Initiate a Sustainability Program
Abstract:Faced with a NYSDEC Consent Order at the WWTP and the results of a NYSERDA energy audit, the City of Oneida developed a strategy for sustainability. Elements of the strategy include dealing with compliance to the Consent Order, developing partnerships with the neighboring Town of Verona and Oneida Indian Nation, and capturing the energy production value of a high strength waste from a large dairy products packaging facility. The ultimate goal of the sustainability program is to allow the WWTP to become energy self-sufficient while operating without permit exceedances.
The first phase of the program was the implementation of an innovative two-stage selector activated sludge process. This process allowed the 2.5 MGD City of Oneida Wastewater Treatment Plant to increase its secondary treatment capacity without adding more unit operations or new tankage. A successful full-scale demonstration was conducted over a 10 month period by modifying one of the two trains of secondary treatment tankage. As a result of these improvements, effluent solids exceedances have been non-existent while handling flows as high as 6.8 MGD. The treatment plant results showed improved settleability of 2nd stage MLSS; the sludge volume index (SVI) dropped from an average of 165 ml/g prior to the selector installation to an average of 95 ml/g after the selector installation.
The second phase of the sustainability program was to increase aeration capacity and improve oxygen transfer efficiency. This was accomplished by installing new turbine blowers and new strip aeration fine bubble diffusers. The equipment selection was done using a Life Cycle Analysis approach. The capital cost for these items was not the least expensive alternative, however the life cycle cost had the most value for the City. A 49% reduction in electrical usage during 2006 was experienced following the installation and start up of the new aeration equipment.
The third phase of the sustainability program is on-site pretreatment of a high strength dairy wastewater using anaerobic technology to generate biogas, which will be used for cogeneration of heat and electricity. Pilot testing of this concept was conducted to gather sufficient information for facility planning and full-scale design. The pilot test results showed the highstrength waste and the process wastewater could be effectively treated. The processing scheme developed was to pretreat the admixture of the two streams using a dissolved air flotation (DAF) unit to remove the bulk of the fats, oils and grease (FOG) and suspended solids. The float solids will go direct to the existing anaerobic digesters, while the subnatant (soluble COD fraction) is to be pretreated in the anaerobic Mobilized Film Technology (MFT) reactor. The combined amount of biogas that would be conservatively produced, 78.5 MMBTU/day based on pilot performance of the DAF and MFT, will be enough to run a 250 kW generator.
The City of Oneida has taken a bad situation, imposition of a Consent Order, and created a sustainability program that is expected to allow the WWTP to become energy independent. The innovative two-stage selector activated sludge process provides additional hydraulic capacity, additional BOD5 removal capacity, and the ability to increase sludge age thus decreasing solids yield. The installation of energy efficient aeration equipment has resulted in a significant electrical usage saving. The anticipated anaerobic pretreatment of a high strength dairy wastewater will yield sufficient energy to allow the WWTP to become energy self-sufficient.
Document Type: Research Article
Publication date: October 1, 2007
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