A "green" score method for asset management is presented which encompasses short-term and long-term economics, risk of asset failure, and long-term environmental impact.The concepts in this paper are built upon recent EPA Region 3 workshops which introduced a spreadsheet model to project 20-year expenditures based on economics and risk of asset failure. Adding a "green" score to the spreadsheet rankings changes the asset management decision paradigm from strictly economical to include both economical and environmental considerations. This allows one to capture items that are more difficult to represent by cash numbers such as environmental sustainability and quality of life factors.
Early in 2005 General Electric Water & Process Technologies (GE) began supplyingCraftMaster Manufacturing, Inc. (CMi) with water treatment chemicals and expertise. A GE/CMi team, composed of operations, technical and management personnel, was established to uncover and address immediate and long term wastewater system problems and issues. The combination of experience and troubleshooting expertise allowed for collaborative work to continuously improve operations, increase reliability and reduce overall costs.
OVERVIEW OF WASTEWATER TREATMENT PROCESSThe main wastewater treatment plant consists of screening, primary and secondary treatment operations, and dewatering. CMi processes 1 -1.5 MGD (158 -237 m 3 /hr) of mill process wastewater and storm runoff water. Figure 1 shows a general schematic of the wastewater treatment system and recycle loop. CraftMaster operates a "zero wastewater discharge" system. Wastewater is treated, then stored in lagoons for recycle to the mill as makeup process water. Some water is purged to sprayers to irrigate fields.
To comply with benzene NESHAP (National Emission Standards for Hazardous Air Pollutants) and MON (Miscellaneous Organic NESHAP) regulations, in 2009 a midwestern chemical plant WWTP was modified and expanded and restarted with two new above ground covered equalization tanks and two new above-ground recirculated aeration tanks. Use of all unlined earthen basins, including a primary sedimentation basin, was discontinued, which resulted in significant hydraulic storage capacity reduction as well as loss of primary treatment. Following startup of the new plant there were several wastewater system upsets resulting in solids carryover from secondary clarifiers. Loading from continuous and batch chemical plant process operations is highly variable. This paper describes two low cost innovative operational and system changes that were enacted in order to reduce occurrences of denitrification and solids carryover in secondary sedimentation clarifiers.
The solid bowl centrifuge has emerged as a dewatering machine of choice in many treatment plants processing biological or mixed sludges. The high G forces promote the formation of highly compacted, dry sludge cake. Other advantages include a small footprint, and an enclosed system that reduces odor. The operating costs include maintenance of a precision-balanced high speed machine, cost of electrical power, and flocculant aids (polymers). This paper will demonstrate how Quality tools from the Six Sigma body of knowledge can be employed to optimize overall sludge processing costs when using a centrifuge. Perhaps many operating centrifuges could increase reliability and reduce overall costs by 25% or more, using these techniques!
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