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It is a common problem in the wastewater industry for a plant wanting to go from ponding or liquid field application of waste sludge to dewatering followed by drying or land application or haulage to a landfill. In accomplishing this process change the dewatering step is critical. If the discharge moisture is too high the landfill won’t take the waste, the energy balance of a Thermal Dryer is primarily a function of moisture, so the overall economics of the project are significantly impacted by the performance of the dewatering stage. What steps should be taken to insure the dewatering process is achieved?
What is typically done is pilot testing with small scale dewatering units. This article will cover the belt press and screw press options and the analysis to use that based on established filtration theory will develop bid specifications that insure the acquired dewatering equipment will meet the process objectives. A perusal of dewatering bid specifications shows few incorporate the specifications items that should be reference if basing the equipment selection on dewatering theory and the pilot test results.
This article will cover a recent pilot trial for determining equipment sizing on a project and go through an analysis of the test results based on filtration theory so that specifications are written that will insure the desired process objectives are met. What are the equipment specifications that relate to filtration theory and process performance, they are in order of their importance:
1. Filtration Area
2. Feed Distribution
3. Gravity Section Control
4. Cake Pressure / Time Under Pressure
5. Drive System: Speed / Control
The article will go through an analysis of all the filtration data that can and should be taken and demonstrate how using filtration theory the bid specifications can be generated that will insure desired process objectives are met.
Brief Biography and/or Qualifications Education: BS Chemical Engineering, Masters Business Administration
1999 to Present: Director Sales and Marketing BDP Industries.
1985 to 1999: Director of Research / Product Development, Eimco Process Equipment Co
1979 to 1985: Project Manager Getty Minerals
1972 to 1979: Project Engineer: Research and Development Group, Eimco
My entire career has been involved in Filtration Technology.
3:45pm - 4:30pm ID: 308 / Session 07B: 2 Main Technical Program Topics: Wastewater Treatment Processes, Solids, Energy Keywords: anaerobic digestion, solids handling, biosolids, biogas, CHP
City Of Moscow Solids Management Alternative Feasibility Study
University of Idaho, United States of America; , ,
This project investigates an upgrade to the solids handling of the City of Moscow’s Water Reclamation and Reuse Facility (WRRF). Currently, waste activated sludge (WAS) is dewatered and transported to Latah Sanitation where it is composted to achieve Class A biosolids status. This is a costly method of solids handling which has few opportunities to realize resource recovery. Additionally, Moscow forgoes primary clarification – opting to treat all influent wastewater in its activated sludge basins.
In this study, anaerobic digestion is considered due to its ability to produce biogas. Biogas, rich in methane, can be used with combined heat and power (CHP) to provide electricity and heat to the WRRF, with the potential to offset operational costs and contribute to achieving resource recovery. Three different high-rate digestion alternatives were considered: single stage, acid-gas phased, and thermal hydrolysis pretreatment coupled with a single stage digester. Due to the complexity and uniqueness of the Moscow WRRF, using thermal hydrolysis to pretreat WAS before digestion proved the best of the three alternatives. However, when compared to the current operations, the disadvantages outweighed those of the current operations resulting in a final recommendation of a “no-build”.
Brief Biography and/or Qualifications Nicole is a senior from Vancouver, Washington studying Civil Engineering at the University of Idaho.
Kenny is a senior studying electrical engineering at the University of Idaho. He has an interest in biogas as it relates to his passion for renewable energy.
Casey is a graduate student at the University of Idaho working on his master’s under Dr. Coats. His research focuses on resource recovery and process modelling. He is expected to graduate in Spring 2019.
Kirsten is a senior at the University of Idaho studying Civil Engineering and Spanish.
4:30pm - 5:15pm ID: 189 / Session 07B: 3 Main Technical Program Topics: Solids Keywords: Thickening, digestion, capacity, biogas
Unlocking Idle Capacity in Old Digesters
Patricia Tam, Chris Muller, Tadd Giesbrecht
Brown and Caldwell, United States of America;
Increasing digester capacity is one of the costliest capital improvements in a wastewater treatment plant. This could take the form of adding new digester tanks, converting to an enhanced digestion process, or upgrading the thickening process. Of these, thickening process improvements could provide significant capacity gain at a cost much lower than the other approaches. This case study is related to the recent upgrade at the Central Kitsap Treatment Plant (CKTP), which includes upgrades to both liquid-stream and solids-stream processes.
The digestion system at CKTP treats primary and waste activated sludge (WAS) generated at CKTP, as well as secondary sludge generated at three other, smaller plants operated by Kitsap County. The two existing anaerobic digesters were approaching capacity and it was not possible to safely and reliably take one unit out of service for maintenance for extensive periods. In addition, the existing boilers could no longer beneficially use the biogas, so that the biogas was routinely combusted in a flare and wasted to the atmosphere.
As part of a larger plant upgrade, the thickening scheme was changed from co-thickening in two existing gravity thickeners to separate thickening of primary sludge thickening in the gravity thickener and WAS thickening in a new rotary drum thickener (RDT). This results in digester feed sludge at about twice the percent solids compared to that prior to the upgrade and doubling of the solids processing capacity of the digestion process. The thicker digester feed sludge also allowed for a new, more efficient energy strategy for the plant. A new combined heat and power (CHP) system was included in the upgrade, which provides beneficial reuse of the biogas, significantly reduces the use of fuel oil while meeting the system process heating needs and producing power, and reduces greenhouse gas (GHG) emissions.
Brief Biography and/or Qualifications Patricia Tam is a process engineer at Brown and Caldwell with 22 years of professional environmental engineering experience. She has extensive experiences in process design and modeling of biological treatment systems, plant capacity assessment, aeration system design, and facility planning. Ms. Tam also has experience in hydraulic modeling, UV disinfection system, odor control, and predictive fate modeling for air emissions.