Calcium hypochlorite

Abstract: Contaminated water causes an estimated 6 to 60 billion cases of gastrointestinal illness annually. The majority of these cases occur in rural areas of developing nations where the water supply remains polluted and adequate sanitation is unavailable. A portable, low-cost, and low-maintenance solar unit to disinfect unpotable water has been designed and tested. The solar disinfection unit was tested with both river water and partially processed water from two wastewater treatment plants. In less than 30 min in midday sunlight, the unit eradicated more than 4 log10 U (99.99%) of bacteria contained in highly contaminated water samples. The solar disinfection unit has been field tested by Centro Panamericano de Ingenieria Sanitaria y Ciencias del Ambiente in Lima, Peru. At moderate light intensity, the solar disinfection unit was capable of reducing the bacterial load in a controlled contaminated water sample by 4 log10 U and disinfected approximately 1 liter of water in 30 min. Contaminated water causes an estimated 6 to 60 billion cases of gastrointestinal illness annually. The majority of these cases occur in rural areas of developing nations where the water supply is polluted with a variety of microorganisms, including viruses, fecal coliforms, and protozoa, and adequate sanitation is unavailable. The need for a low-cost, low-maintenance, and effective disinfection system for the improvement of water quality is high. Conventional technologies used for disinfection of unpotable water include ozonation, chlorination, and artificial UV radiation. These technologies are capital intensive, require sophisticated equipment, and demand skilled operators (1, 16, 22). At the household level, boiling water for about 10 min or the use of certain chlorine compounds available in tablets (halazone or calcium hypochlorite) or solutions (sodium hypochlorite at 1 to 2 drops per liter) is commonly used to disinfect

Abstract: Epidemiologic investigations of the Latin America cholera epidemic have repeatedly implicated untreated drinking water and water touched by hands during storage as important vehicles for disease transmission To prevent such transmission, we provided a new narrow-mouthed, plastic, water storage vessel and 5% calcium hypochlorite solution for home disinfection of stored water to a Bolivian Aymara Indian community at risk for cholera We evaluated acceptance of this intervention and its effect on water quality Each of 42 families in the study obtained water from a household well; fecal coliform bacteria were found in water from 39 (93%) of 42 wells and 33 (79%) of 42 usual water storage vessels One group of families received the special vessels and chlorine (group A), a second received only the special vessels (group B), and a third served as a control group (group C) Water samples collected every three weeks from group A special vessels had lower geometric mean fecal coliform colony counts (P < 00001) and lower geometric mean Escherichia coli colony counts (P < 00001) than water from group B or C vessels Adequate levels of free chlorine persisted in these vessels for at least 5 hr The special vessels and chlorine solution were well accepted and continued to be used for at least six months Use of the vessel and chlorine solution produced drinking water from nonpotable sources that met World Health Organization standards for microbiologic quality

Abstract: The objective of this study was to determine the effectiveness of chlorine, chlorine dioxide, ozone, and hydrogen peroxyacetic acid (HPA) treatments on the degradation of mancozeb and ethylenethiourea (ETU) in apples. This study was based on model experiments at neutral pH and temperature. Fresh apples were treated with two different levels of mancozeb (1 and 10 microg/mL). Several of the treatments were effective in reducing or removing mancozeb and ETU residues on spiked apples. Mancozeb residues decreased 56-99% with chlorine and 36-87% with chlorine dioxide treatments. ETU was completely degraded by 500 ppm of calcium hypochlorite and 10 ppm of chlorine dioxide at a 1 ppm spike level. However, at a 10 ppm spike level, the effectiveness of ETU degradation was lower than observed at 1 ppm level. Mancozeb residues decreased 56-97% with ozone treatment. At 1 and 3 ppm of ozone, no ETU residue was detected at 1 ppm of spiked mancozeb after both 3 and 30 min. HPA was also effective in degrading the mancozeb residues, with 44-99% reduction depending on treatment time and HPA concentrations. ETU was completely degraded at 500 ppm of HPA after 30 min of reaction time. These treatments indicated good potential for the removal of pesticide residues on fruit and in processed products.