City of Columbus Utilities
Columbus, Indiana
In recent years there has been an exponential rise in concern and interest regarding global
warming trends, with the evidence becoming increasingly stronger that climate change is a
result of greenhouse gases (GHGs) emitted largely by human activity. The GHGs of most
concern are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3),
chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), perfluorinated carbons (PFCs), and
sulfur hexaflouride (SF6). By far the most common of the GHGs is CO2, but several of the
other GHGs have considerably stronger effects on global warming potential relative to their
total mass, and at least two of them (CH4 and N2O) are common to wastewater treatment.
Wastewater treatment facilities are not considered to be among the top producers of GHGs
from human activity; however, a more holistic view of wastewater management indicates that
its impacts on GHG emissions spread into other sectors of GHG production. Because of their
engineered nature, wastewater treatment facilities represent significant opportunities to reduce
GHG emissions. It follows that when a municipality is planning new wastewater treatment
facilities, the evaluation of treatment alternatives needs to consider the relative impacts of
those alternatives on GHG emissions. Sustainability principles also need to be incorporated
into the evaluation methodology.
This paper presents a case study evaluation of wastewater management alternatives including
GHG-emissions and overall “carbon-footprint.” This case study is for a future, greenfield-type
wastewater treatment facility in Columbus, Indiana. The evaluation demonstrates how
different wastewater management options present differing impacts on GHG emissions and
carbon sequestration. Consequently, the impacts of GHG emissions and carbon management
need to be part of the wastewater facility planning process.
Using a decision science approach, the evaluation compares potential impacts of wastewater
management alternatives for new wastewater treatment facilities (19-mgd design capacity).
Five different treatment alternatives were evaluated, with three of those alternatives involving
sub-options, for a total of eight treatment scenarios investigated:
This paper summarizes the results of the evaluation and demonstrates how traditional and
non-traditional wastewater management options are affected by their impacts on carbon
management and their potential for reductions in GHG emissions. It is concluded that the
evaluation of the GHG-emission impacts and “carbon footprints” of wastewater treatment can
and should be considered when evaluating alternatives for the design and implementation of
water reclamation facilities.
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Posted: July 29th, 2010 | Filed under: Sanitary Sewer, Stormwater, Waste Water Treatment | Tags: Biosolids Management, Decreased Energy Consumption, Environmental Impact, Plant Sustainability, Reduced Carbon Footprint | No Comments »
The Metropolitan Water Reclamation District of Greater Chicago
Chicago, Illinois
Recently, more and more wastewater treatment plants (WWTPs) are upgrading their conventional solids treatment systems which produce Class B biosolids to produce Class A biosolids. This trend has triggered rapid growth of not only new sludge treatment technologies but also conventional treatment modification technologies. The main focus of this paper is on anaerobic digestion process modification techniques to produce Class A biosolids or enhanced digestion to achieve multiple solids processing objectives. The paper is based on information collected from various WWTPs throughout the US on practices and trends to enhance sludge digestion, worldwide literature review, and from technology vendors. A systematic analysis (case studies) of 4 WWTPs to evaluate and shortlist alternatives to enhance the existing solids thickening-anaerobic digestion-dewatering complex into either Class A or enhanced solids processing system as well as estimation of the operational carbon footprint (OCF) of each of the alternatives are presented in this work. Carbon footprint analysis of all the recommended options showed that Class B systems have smaller footprint than Class A or enhanced digestion systems mainly due to the higher heat and power requirements. Class B conventional anaerobic digestion ratio of OCF footprint to volatile solids loading to digesters (OCF/VSL) for solids processing part of plants is in the range of 0.45-0.55 [mass of CO2/mass of volatile solids]. Class A and enhanced digestion systems OCF/VSL do not vary greatly from each other, being in the range of lowest 0.52 for TPAD in continuous operation mode to 0.6-0.7 for the other modifications. Further heat and energy requirement analysis demonstrated that although all enhanced digestion systems result almost in the same carbon footprint, TPAD and OpenCEL require less electricity and natural gas supply from the outside sources due to higher biogas production and further heat recovery. More detailed analysis of heat and power requirements for each system at each of the plants should be performed in order to identify the most suitable option. This analysis should also include calculations of capital cost, carbon footprint associated with installations and maintenance, estimation of social factors and economic benefits of each of the systems. Source: WEFTEC 2009 Proceedings
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Posted: July 6th, 2010 | Filed under: Waste Water Treatment, Water Treatment | Tags: Biosolids Management, Reduced Carbon Footprint | No Comments »
Alexandria Sanitation Authority
Alexandria, Virginia
The Alexandria Sanitation Authority (ASA) operates a 54 mgd Advanced Wastewater Treatment Facility (AWTF) in Alexandria, Virginia. ASA has been awarded Tier 4 Platinum Certification under the National Biosolids Partnership (NBP) for its Biosolids EMS and under the Virginia Environmental Excellence Program (VEEP) has been awarded E3 (Exemplary Environmental Enterprise) status. This paper provides a case study for merging separate EMS systems including a summary of the process and lessons learned that will be of interest to facilities that currently have or are considering an EMS. It was learned that the following steps are part of a successful merging of management systems at ASA: 1) develop boundary conditions for the merger, such as maintaining certification from external auditors and organizations, and identifying organizational goals, such as streamlining staff efforts and documentation; 2) perform a baseline review of requirements for the MSs to identify similarities and differences; 3) develop alternatives for merging the MS which could range from a full merger into one EMS program, or where that is not practical, to streamlining terminology and documentation; and 4) develop an implementation plan that includes communication and training for all staff and awareness of timing of external audits. Source: WEFTEC 2009 Proceedings
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Posted: July 6th, 2010 | Filed under: 100K-500K, Waste Water Treatment | Tags: Biosolids Management | No Comments »
Encina Wastewater Authority
Carlsbad, California
The Encina Wastewater Authority (EWA) recently upgraded the biosolids and energy management facilities at the Encina Water Pollution Control Facility (EWPCF) in Carlsbad, California. Biosolids processing improvements included replacement of existing dewatering equipment with centrifuges and the installation of a triple-pass, rotary drum heat dryer system to produce Class A biosolids pellets for beneficial reuse. As an integral part of its expansion project, EWA prepared a Biosolids Management Plan (BMP) through a multifaceted process that included formulation of evaluation factors for the decision framework, surveys of potential endusers, evaluation of various reuse/disposal (R/D) options using economic and qualitative analyses, generation of a Financial Model, preparation of a Business Plan, and other related elements. This paper presents an overview of the BMP, focusing on the major planning elements, development process, and several unique features that make the approach used in the BMP a valuable tool for development of EWA’s biosolids distribution and marketing program. Source: WEFTEC 2009 Proceedings
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Posted: July 6th, 2010 | Filed under: 100K-500K, Waste Water Treatment, Water Treatment | Tags: Biosolids Management, Cost Savings, Environmental Impact, Innovative Approach | No Comments »