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Published on: September 26, 2016
Coliforms removal in full-scale activated sludge plants in India
A A Kazmi1, V K Tyagi, R C Trivedi
1Department of Civil Engineering, Indian Institute of Technology, Roorkee 247667, India. kazmifce@iitr.ernet.in
Journal of Environmental Management
|April 6, 2007
Summary
Activated sludge plants in India showed moderate removal of total coliforms (TC) and fecal coliforms (FC). High mixed liquor suspended solids (MLSS) and sludge retention time (SRT) in extended aeration (EA) improved removal efficiency.
Area of Science:
- Environmental microbiology
- Wastewater treatment engineering
Background:
- Coliform removal in wastewater treatment is crucial for public health and environmental safety, especially for irrigation use.
- Existing activated sludge plants (ASP) in Northern India face challenges meeting World Health Organization (WHO) standards for coliforms in effluent.
Purpose of the Study:
- To investigate coliform removal efficiency in full-scale activated sludge plants (ASP) in Northern India.
- To identify operational parameters influencing coliform removal.
- To explore the relationship between coliforms and key wastewater quality indicators.
Main Methods:
- Analysis of total coliforms (TC) and fecal coliforms (FC) removal in operating ASP.
- Evaluation of extended aeration (EA) process performance under varying mixed liquor suspended solids (MLSS) and sludge retention time (SRT).
- Correlation analysis between coliform levels, biochemical oxygen demand (BOD), and suspended solids (SS).
Main Results:
- Log2.2 and log2.4 removal rates for TC and FC, respectively, were observed.
- Effluent coliform counts exceeded permissible limits for unrestricted irrigation.
- Extended aeration (EA) with high MLSS and SRT demonstrated superior coliform removal.
- Linear relationships with good correlation were found between BOD, SS, and coliforms.
Conclusions:
- Wastewater microbiological quality improvement is strongly linked to suspended solids (SS) removal.
- Suspended solids (SS) can potentially serve as a regulatory parameter for coliform control in wastewater effluent.
- Optimizing SRT and MLSS in EA processes can enhance coliform reduction.
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