Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Chemical and Biochemical Engineering

Supervisor

Ray, A.

Abstract

Combined sewer overflows (CSOs) contain a highly variable, wide range of contaminants, both in particulate and soluble form, making conventional water treatment processes unable to offer adequate public health protection. To date, no study proposed an efficient and cost-competitive treatment able to remove a broad spectrum of CSO pollutants. This research demonstrated that a chemical pre-treatment, followed by micro-sieve filtration and UV disinfection is an efficient and cost-competitive treatment for CSOs. Pollutant removal was achieved by first adsorbing soluble pollutants on zeolite and powdered activated carbon, and subsequently applying filtration carried out by polymer-enhanced microsieving. Optimal treatment condition, consisting of 1.1 mg/L of the cationic polymer, 250 mg/L of zeolite, and 5 mg/L of powdered activated carbon, was identified. Under this condition, expected performance would be reductions of 72%, 56%, 35%, and 75% for turbidity, total Kjeldahl nitrogen, total chemical oxygen demand, and total phosphorous, respectively. The efficiency of UV disinfection with and without chemical pre-treatment was investigated and a microbial inactivation kinetic model was developed. Experimental results reported that 4-log removal of FC was achieved at fluence 10 mJ/cm2 when the UV disinfection was enhanced by chemical pre-treatment and microsieving filtration using a 32 µm mesh size. Under these conditions, the TSS removal achieved was 73% and the UVT increase of 32%. These findings demonstrate the possibility to quickly and effectively treat CSOs by reducing equipment and operating costs, providing municipalities with viable and low footprint treatment options where the issues of CSO and nutrient management are simultaneously tackled.

Summary for Lay Audience

Combined sewer overflows (CSOs) contain a highly variable, wide range of contaminants, making conventional water treatment processes unable to offer adequate public health protection. Treating combined sewer overflow discharges is necessary to reduce the amount of pollutants discharged into rivers, lakes, or seas. To overcome CSO impacts, new and adaptable multifunctional treatment schemes need to be developed. To date, to the best of our knowledge, no study proposed an efficient and cost-competitive treatment able to remove a broad spectrum of CSO pollutants. This research demonstrated that a chemical pre-treatment, followed by micro-sieve filtration and UV disinfection is an efficient and cost-competitive treatment process able to simultaneously remove combined sewer overflow pollutants (i.e. suspended solids, chemical oxygen depends, turbidity, and fecal bacteria) in conjunction with nutrient (nitrogen and phosphorus). The removal of particulates, as well as dissolved nitrogen and phosphorus, was achieved by first adsorbing soluble pollutants on zeolite and powdered activated carbon, and subsequently applying filtration carried out by polymer-enhanced microsieving. An optimal treatment condition, consisting of 1.1 mg/L of the cationic polymer, 250 mg/L of zeolite, and 5 mg/L of powdered activated carbon, was identified by Pareto analysis. Under this condition, expected performance would be reductions of 72%, 56%, 35%, and 75% for turbidity, total Kjeldahl nitrogen, total chemical oxygen demand, and total phosphorous, respectively. Moreover, the efficiency of UV disinfection with and without chemical pre-treatment was investigated and a microbial inactivation model able to predicts the inactivation of fecal coliform (FC) bacteria was developed. Experimental results reported that 4-log removal of FC was achieved at fluence 10 mJ/cm2 when the UV disinfection was enhanced by chemical pre-treatment and microsieving filtration using a 32 µm mesh size. Under these conditions, the TSS removal achieved was 73% and the UVT increase of 32%.

The findings presented in this thesis demonstrate the possibility to quickly and effectively treat a large amount of wastewater flow by reducing equipment and operating costs, providing municipalities with viable and low footprint treatment options where the issues of combined sewer overflow and nutrient management are simultaneously tackled.

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