Evaluation of hydrogen sulphide concentration and control in a sewer system.
ABSTRACT This study focused on monitoring hydrogen sulphide (dissolved and atmospheric) generation and wastewater volumetric flow in a 21.4 km sewer line of the City of San Antonio, Texas. The results were used to evaluate daily and seasonal trends of atmospheric and dissolved sulphide, and to better apply sulphide control using ferrous sulphate to prevent odour and sewer pipe deterioration. As part of this study, the evaluation of a cost-effective dosing strategy with ferrous sulphate was performed to better control the sulphide contents in wastewater. Dosing studies were performed in the laboratory to find the required ratio of ferrous sulphate for acceptable sulphide removal. The results indicate a 1.25 mole ratio requirement, to reduce sulphide by 93%. Over a typical daily diurnal cycle, necessary dosing rates to maintain sulphide concentrations below 2mg varied between 0 and 36,777 mold(-1) with a daily average rate of 14,438 mol d(-1). If, instead of dosing at the maximum required rate, dosing was matched over the diurnal cycle, chemical savings would amount to 22,339 mold(-1) while achieving sulphide control. The approximate cost of the ferrous sulphate solution dosed is $0.14 per mol and this amount of chemical savings translates into roughly $2923 per day. Actual dosing cost for the hypothetical average day will be $1889 per day. These cost savings can easily recoup the required instrumentation costs to achieve this diurnal dose matching.
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ABSTRACT: Millions of dollars are being spent worldwide on the repair and maintenance of sewer networks and wastewater treatment plants. The production and emission of hydrogen sulphide has been identified as a major cause of corrosion and odour problems in sewer networks. Accurate prediction of sulphide build-up in a sewer system helps engineers and asset managers to appropriately formulate strategies for optimal sewer management and reliability analysis. This paper presents a novel methodology to model and predict the sulphide build-up for steady state condition in filled sewer pipes. The proposed model is developed using a novel data-driven technique called evolutionary polynomial regression (EPR) and it involves the most effective parameters in the sulphide build-up problem. EPR is a hybrid technique, combining genetic algorithm and least square. It is shown that the proposed model can provide a better prediction for the sulphide build-up as compared with conventional models.Environmental Technology 02/2014; DOI:10.1080/09593330.2014.881403 · 1.20 Impact Factor
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ABSTRACT: Concrete sewer pipes are known to suffer from a process of hydrogen sulfide gas induced sulfuric acid corrosion. This leads to premature pipe degradation, performance failure and collapses which in turn may lead to property and health damage. The above work reports on a field study undertaken in working sewer manholes where the parameters of effluent temperature and pH as well as ambient temperature and concentration of hydrogen sulfide were continuously measured over a period of two months. Early results suggest that effluent pH has no direct effect on hydrogen sulfide build up; on average the effluent temperature is 3.5°C greater than the ambient temperature inside the manhole and also it was observed that hydrogen sulfate concentration increases with increasing temperature.