Many wastewater utilities are developing or have recently developed biosolids management
plans (BMP) that provide a strategy for 20 to 25 years into the future. In developing BMPs,
wastewater utilities are faced with many challenges, such as satisfying the customer base,
satisfying internal and external stakeholders and developing a BMP that is affordable,
sustainable for the future and meets regulations. Traditionally, small, medium and some largesized
wastewater utilities have land applied anaerobically digested Class B biosolids either as
liquid or dewatered cake, while several of the larger wastewater utilities have thermally oxidized
their biosolids. With growing public pressure to reduce or cease land application, there has been
renewed interest in thermal oxidation as a management strategy, often raising the question: is it
sustainable? If the wastewater utility has existing digestion, is thermal oxidation compatible with
digestion or should digestion be stopped?
This paper presents a comparison of six different thermal oxidation process schemes with respect
to their economic, energy and carbon footprints for undigested and digested solids. The results of
the comparison provide wastewater utility staff and engineers with the positive answer to the
question “Is thermal oxidation of biosolids with energy recovery sustainable?”
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Posted: May 20th, 2011 | Filed under: Waste Water Treatment, Water Treatment | Tags: Cogeneration, Energy Recovery, Environmental Impact, Green Infrastructure, Plant Optimization, Plant Sustainability, Reduced Carbon Footprint, Reduced Greenhouse Gas Emissions, Thermal Oxidation | No Comments »
Northeast APCF
Clearwater, Florida
The City of Clearwater, Florida maintains and operates three wastewater treatment plants. The 5 mgd East Advanced Pollution Control Facility (APCF), the 13.5 mgd Northeast APCF, and the 10 mgd Marshall Street APCF. Both Northeast APCF and Marshall APCF use anaerobic digesters for biosolids handling. The biosolids from East APCF is hauled and processed at Northeast APCF. During the early 2000’s the city experienced poor results from their digesters, due to deteriorated heating and mixing equipment. Consequently the City embarked on an initiative to invest in a rehabilitation program for all their digester facilities. The purpose of this paper is to provide data on increased gas production and reduced hauling cost savings after the digesters were rehabilitated in late 2006. The data from the Northeast APCF is presented. The intent of the Clearwater Anaerobic Digester Improvements Project is to improve biosolids treatment processes at the APCFs, to enhance and improve disposal options and operational flexibility, to promote biosolids reuse and energy recovery, and to reduce operating costs as feasible at the facility. Placing the anaerobic digesters back into service reduced approximately 40 percent of the residuals volume. By rehabilitating and utilizing the anaerobic digesters over the past five years WPC has generated O&M savings of $1,711,000. If nothing had been accomplished to reduce the volume of biosolids hauled, the present day annual cost would be $1,424,700. Another added benefit is the reduction in fossil fuel not hauling 14,210 wet tons per year. This equates to 63 truckloads annually. It is also rare to be able to have the opportunity to roll back and reduce costs to a rate lower than they were six years ago while dealing with an increase in unit cost. Source: WEFTEC 2009 Proceedings
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Posted: August 27th, 2010 | Filed under: Waste Water Treatment | Tags: Cost Savings, Energy Recovery, Improved Disposal Options, Reduced Carbon Footprint | No Comments »