Theoretical analysis of physicochemical processes occurring during water treatment by ozone and ultraviolet radiation

Author : N.A. Mishchuk, V.V. Goncharuka and V.F. Vakulenkoa

Abstract

The paper presents a kinetic model developed for ozone dissolution in water and taking into account convective and diffusion processes occurring in the vicinity of floating bubbles that contain an ozone-air mixture. It was shown that the gradient of ozone concentration in a convective-diffusion layer and consequently the rate of ozone transfer from bubbles to the solution depended on the rate of ozone decomposition both in its reaction with organic admixtures and in the conditions of exposure to ultraviolet radiation.

The obtained kinetic curves of destruction of organic compounds and changes of ozone concentration in water and ozone-air mixture are compared with experimental data for humic acids. The paper also analyzes additional factors affecting the kinetics of ozone dissolution and the rate of resultant reactions.

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Incorporation of sludge waste from water treatment plant into red ceramic

Author: S.N. Monteiroa, J. Alexandreb, J.I. Margemc, R. Sáncheza and C.M.F. Vieira


Abstract

The influence of the firing temperature on the technological properties of red ceramics made of a kaolinitic clay incorporated with a sludge from water treatment plant was evaluated. The sludge was initially submitted to characterization tests to determine its particle size distribution, chemical composition, mineralogical composition, thermal behavior and morphological aspects. Mixtures were prepared with amounts of 0, 3, 5 and 10 wt% of sludge incorporated into the clayey body. Rectangular specimens were obtained by 20 MPa pressure molding and then fired at 700, 900 and 1100 °C in a laboratory furnace. Ceramic properties related to the bulk density, linear shrinkage, water absorption and flexural rupture strength were determined. The results indicated that the incorporation of the sludge increase the water absorption and reduce the mechanical strength of the clayey fired ceramic. This is a consequence of the changes caused in the porosity by the relatively elevated weight loss during the firing stage.

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Disinfection by-products and their precursors in a water treatment plant in North China: Seasonal changes and fraction analysis

Author: Chao Chena, Xiao-jian Zhanga, Ling-xia Zhua, Jing Liua, Wen-jie Heb and Hong-da Hanb

Abstract

A one-year-long monitoring project was conducted to assay the concentrations of THMs, HAAs and their formation potential along the conventional process in a water treatment plant in North China. Subsequent investigations of organic matter fractionation and the contribution of the algae to the precursor were also conducted to trace the source of the DBPs. The results showed that the concentration of DBPs and their formation potential varied with the seasons. The highest concentrations of THMs and the highest HAAs formation potential, each almost 500 µg/L, were detected in autumn and the lowest were in spring, no more than 100 µg/L. Both organic matter and algae were found to be important DBP precursors. The hydrophobic acid fraction in dissolved organic matter has the highest formation potential for both THM and HAA. Algae contribute about 20% to 50% of the total formation potential during an algal bloom. The efficiency of each unit process for DBPs and precursors was also assayed. Unfortunately, the conventional drinking water treatment process is limited in its efficiency for precursor removal. The pre-chlorination and filtration process had a negative effect on DBP or precursor removal.

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Critical evaluation of wastewater treatment and disposal strategies for Istanbul with regards to water quality monitoring study results

Abstract

Urban Wastewater Treatment and Marine Outfall Facilities are being planned in accordance with Istanbul Water Supply and Wastewater Treatment and Disposal Master Plan prepared for Istanbul Water and Sewerage Administration (ISKI) in 1999. According to the Master Plan, ISKI initiated in 1996 the water quality monitoring program of receiving water bodies conducted by the Istanbul University (IU) Institute of Marine Sciences and Management and Istanbul Technical University (ITU) Environmental Engineering Department. The monitoring program has been carried out for 10 years in 28 stations in the marine environment. In this paper, the results of experimental investigations conducted for parameters including dissolved oxygen, total organic carbon (TOC), particulate organic carbon (POC), Total-N, Total-P, chlorophyll a, structure of benthic community, turbidity and coliforms have been critically analysed taking into consideration the marine outfall and surface water discharges from Istanbul's major wastewater treatment plants together with the transboundary pollution sourced by the Black Sea. The studies reveal that the water quality in the Marmara Sea is deteriorated more than anticipated before, and it is a necessity to develop international cooperation aimed for taking more effective measures in the area.

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