The effect of suspended solids during UV/hydrogen peroxide advanced oxidation of municipal wastewater

As wastewater and water reuse practices evolve to meet changing effluent requirements, the capabilities of various technologies to achieve treatment objectives merit investigation. This work examines the influence of suspended solids on the efficiency of the UV-H2O2 advanced oxidation process to affect oxidation of organic contaminants in biologically wastewater effluents. Effluent samples from two conventional activated sludge plants were used to produce microfiltrates with 0.2 mum nylon filters. Para-chlorobenzoic acid (pCBA) was used as a probe compound to indirectly quantify the steady state OH concentration in samples spiked with H2O2 and irradiated using a bench-scale UV collimated beam apparatus. An effluent sample from a membrane bioreactor was also evaluated. No significant difference in steady state OH concentration was observed between unfiltered and microfiltered samples, suggesting that suspended solids may not significantly contribute to hydroxyl radical scavenging in such effluents. Implications to the role of filtration are discussed

Drinking water quality management progress in Ontario, two decades after Walkerton

Following the waterborne disease outbreak in Walkerton, Ontario, the province made significant efforts to implement recommendations of the public inquiry that resulted. As Ontario reformed its drinking water sector, other jurisdictions were advancing risk-based quality management frameworks for drinking water, including the World Health Organization (WHO) through its water safety plan (WSP) framework. Two decades after the Walkerton tragedy, this paper seeks to: (i) evaluate alignment of Ontario’s Drinking Water Quality Management Standard (DWQMS) with the WSP framework (ii) review readily available data for evidence that Ontario’s DWQMS implementation has improved drinking water safety and promoted a preventive approach through risk-based quality management. Our study found strong alignment between the Ontario DWQMS and WSP frameworks, with supporting programmes and risk assessment procedures present. Analysis of available regulatory data revealed abundant reporting of water quality and adverse incidents in municipal water systems. However, performance data were publicly available, the use of percentage scores for water quality testing obscures the details of system performance and water safety. Reports describing the DWQMS plan and audit results were difficult to obtain and not standardized. There is a need to develop mechanisms to ensure continual improvement of the DWQMS

The use of 185 nm radiation for drinking water treatment

The treatment of water via 185 nm radiation allows for the oxidative degradation of trace organic contaminants without the need for chemical addition. Critical information required for the practical application of such a process has been lacking. Carbamazepine was determined to be an ideal probe compound for study of the 185 nm regime due to negligible direct photolysis at 254 nm. An increase in probe degradation rate due to 185 nm is observed with increasing temperature when water is the only significant absorber of photons. A comparison with the temperature dependence of the 254 nm - H₂O₂ process is made and a fundamental explanation proposed. Experimental evidence reveals that probe degradation rate is strongly influenced by anionic composition at environmentally relevant concentrations, particularly chloride. Evidence for the role of the chlorine radical is obtained by kinetic studies involving select probes, radical scavengers, and ionic strength. Interactions between the major organic and inorganic solutes indicate that resulting degradation kinetics are highly sensitive to the composition of the water matrix, a fact that has been neglected from the literature. A method to quantify molar absorption coefficients is developed that is not prone to errors due to stray radiant energy or wavelength inaccuracies. A method to quantify the 185:254 nm output of a low pressure mercury lamp is presented with results in agreement with values reported in the literature. In addition to the hydroxyl radical (*OH), other radical species such as chlorine (C1*) and sulphate (SO₄*¯) are proposed to be involved in oxidative degradation of trace organics in the 185 nm regime. This suggests that the degradation rate of a given target contaminant depends on the composition of the water matrix, the second-order rate constants with the relevant radicals, and the relative reaction rate constants of the target and the matrix.Applied Science, Faculty ofGraduat

Drinking water quality management progress in Ontario, two decades after Walkerton

Following the waterborne disease outbreak in Walkerton, Ontario, the province made significant efforts to implement recommendations of the public inquiry that resulted. As Ontario reformed its drinking water sector, other jurisdictions were advancing risk-based quality management frameworks for drinking water, including the World Health Organization (WHO) through its water safety plan (WSP) framework. Two decades after the Walkerton tragedy, this paper seeks to: (i) evaluate alignment of Ontario's Drinking Water Quality Management Standard (DWQMS) with the WSP framework (ii) review readily available data for evidence that Ontario's DWQMS implementation has improved drinking water safety and promoted a preventive approach through risk-based quality management. Our study found strong alignment between the Ontario DWQMS and WSP frameworks, with supporting programmes and risk assessment procedures present. Analysis of available regulatory data revealed abundant reporting of water quality and adverse incidents in municipal water systems. However, performance data were publicly available, the use of percentage scores for water quality testing obscures the details of system performance and water safety. Reports describing the DWQMS plan and audit results were difficult to obtain and not standardized. There is a need to develop mechanisms to ensure continual improvement of the DWQMS. HIGHLIGHTS The Ontario DWQMS aligns with the World Health Organization's WSP framework for risk-based drinking water management.; Ontario's DWQMS is a unique example in North America's water industry as a comprehensive and regulated WSP framework.; Existing system performance data are abundant but predominantly focused on regulatory outcomes.; Third-party auditors review QMS systems, but available standardized conformance data are limited.