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| Publication: |
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Operation of Municipal Wastewater Treatment Plants
Manual of Practice-MOP 11 SixthEdition
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| Medium: |
| Download Chapter |
| Pages |
| 69 |
| Publisher: |
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Water Environment Federation (WEF) |
| Year: |
| 2007 |
| Order No: |
| MOP1124 |
| DOI: |
| 10.2175/1-57278-232-3-24 |
Table of Contents
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Index
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Cover Art
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Frontmatter
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| Order Additional Chapters of MOP 11 |
Order a Hard Copy of MOP 11
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Abstract:
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In general, wastewater treatment processes fall into three broad classes: biological, chemical, and physical. Trickling filters, rotating biological contactors, activated sludge, and anaerobic digestion are examples of biological processes. Examples of chemical processes are heavy metal precipitation, phosphorus precipitation, acid or alkali addition for pH control, and disinfection with chlorine or hypochlorite. Processes such as flow measurement, grit removal, primary and secondary clarification/sedimentation, filtration, and centrifugation are examples of physical processes.
At the time of this writing, most wastewater treatment plants in the United States provide preliminary, primary, and secondary levels of treatment to wastewater, where the focus is on reducing carbonaceous biochemical oxygen demand (CBOD) and total suspended solids (TSS) to meet discharge permit parameters. However, to further enhance the quality of receiving waters, regulatory agencies are increasingly targeting reductions in parameters such as nitrogen and phosphorus and pollutants such as metals and non-biodegradable soluble organics, in addition to the conventional BOD,, TSS, and fecal coliform parameters. Another area of regulatory and environmentalist focus is in providing additional (tertiary) treatment to secondary effluent to levels where it can be recycled for applications traditionally served by potable water, such as many types of irrigation and industrial uses. Both of these objectives can be addressed by physical-chemical processes, where either chemical addition can be used to enhance the reduction of conventional parameters such as suspended solids, or new processes can be added to reduce the levels of parameters such as phosphorus and soluble, nonbiodegradable chemical oxygen demand (COD).
Accordingly, this chapter mainly addresses the use of physical-chemical treatment as it relates to (a) enhanced suspended solids reduction in primary treatment, (b) further reduction of solids in advanced treatment processes following conventional treatment, and (c) reductions in parameters such as phosphorus and soluble, nonbiodegradable COD. Other physical, physical-chemical, or chemical treatment methods are discussed extensively elsewhere in this book and the reader is referred to the appropriate chapters. Solids-handling processes that incorporate elements of physical and chemical treatment are also not discussed here, as they too are discussed extensively in other chapters of this book. Advanced biological treatment for nitrogen and phosphorus reduction, which is becoming increasingly more commonplace as opposed to physical-chemical removal, especially at larger wastewater treatment plants, is also discussed elsewhere in this book.
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©2000 Water Environment Federation