Neeta Thacker

Trihalomethane Formation Potential and Concentration Changes During Water Treatment at Mumbai (India)

The treated water at the outlet oftreatment plants and representative servicereservoirs of Mumbai city have been evaluatedfor trihalomethane formation potential in1995–1996. Chloroform, dichlorobromomethane,chlorodibromomethane and bromoform have beenmonitored during monsoon, winter and summer.The levels of chloroform are found above theregulated WHO guideline value of 200 μg L-1 in final water during postmonsoon atGhatkopar (226 μg L-1), Malbar (210.3 μg L-1) and Tulsi (231.26 μg L-1).

Trihalomethane formation potential in treated water supplies in urban metro city

Trihalomethane (THM) formation potential (TFP) is very useful test to assess the level of the formation of trihalomethanes in worst case scenario. Organics in water have the potential to generate harmful disinfection by-products (DBPs) such as THMs, as a result of their reaction with disinfectant chlorine used in drinking water. DBPs are increasingly recognized as cancerous agents. TFP of postchlorinated treated water were investigated at six water treatment plants (WTPs) in Delhi City (India). The present paper presents the current trends of TFP so that prevention and control measures can be initiated by the regulating agencies responsible for drinking water supply. Liquid–liquid extraction method, followed by qualitative and quantitative estimation by gas chromatograph equipped with electron capture detector, had been used for the determination of THMs in water samples collected at the outlet just before supplying to the consumers during 2000–2007. The TFP values from 2004 onward of all WTPs did not exceed the WHO guideline value of ≤1.

Evaluation of mass-transfer coefficient of free fall: Cascade-aerator

The mass-transfer coefficient of a free-fall cascade-aeratorunit of 15 million litres per day was evaluated for its efficiency in the removal of a class of volatile organics, the trihalomethanes(THMs). These compounds are carcinogenic and occur as a resultof chlorination of natural waters. Due to the volatile nature ofthe THMs, the efficiency of aeration as a potential techniquefor their removal has been studied. The principle behindaeration is gas-transfer, according to which the gas-liquidinterface is hypothesized to consist of a gas and liquid filmthrough which gas is transferred by molecular diffusion untilequilibrium is attained. The overall mass transfer coefficient(KL) of the aerator considering oxygen as the reference compound, was found to be29.3 hr-1 for THMs.

Remediation of Dioxins Contaminated Soil Using UV Radiations in Conjunction with Groundnut Oil

The effect of UV radiations and oil mediated UV radiations in removal of PCDDs and PCDFs congeners was studied. The effectiveness of photolytic degradation using groundnut oil was examined for removing tetra-, and octachlorinated congeners of dioxins and furans from contaminated soil by varying the intensity of UV radiation, exposure period and analyte concentration. All the four congeners tested were successfully degraded. The maximum removal of 50.61–62.3% of 2, 3, 7, 8-TCDD, 44.1–69.24% of 2, 3, 7, 8-TCDF, 35.0–56.03% of OCDD and 37.11–59.64% of OCDF was observed at an initial concentration of 2.5 and 5.0 ng g−1 respectively after an UV exposure period of 24 h. The dioxin congeners in the soil sample showed decrease in concentration with the increase in the exposure time and intensity of UV radiations. More degradation of dioxin was found when the samples were exposed for 34 h using 400 W of UV lamp. The rate of photocatalytic degradation of polychlorinated dioxins was found to decrease with the increase in number of chlorines.