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Bacterial removal during electrocoagulation (EC) was investigated employing samples from four different water/wastewater sources, namely, greywater, river water, secondary treated sewage and tap water spiked with Escherichia coli. Effects of current density and electrolysis time on the bacterial removal with aluminium electrodes were evaluated. For greywater, river water and secondary treated sewage, total coliform and E. coli removal efficiencies were not significantly different for the tested samples and varied in the range of 2.22-2.53 log10 units at a current density of 1 mA/cm² and electrolysis time of 30 min. Higher removals up to 3.80 log10 units could be obtained at higher current density of 5 mA/cm². Heterotrophic bacterial removals were higher compared with coliforms for the tested samples. Further, higher removal was obtained with spiked E. coli in tap water compared with naturally occurring coliforms in other samples. A comparison of bacterial removal by chemical coagulation (CC) employing alum at optimum dose with that by EC with 1 mA/cm² current density and 30 min electrolysis time showed significantly higher removal by EC (2.22-2.53 log10 removal) compared with CC (1.40-1.80 log10 removal) for the three tested samples. Upon storage up to 48 h, no significant regrowth/decay of organisms was observed in the EC-treated samples. [ABSTRACT FROM AUTHOR]

In recent years, response surface methodology (RSM) has been used for modelling and optimising a variety of water and wastewater treatment processes. RSM is a collection of mathematical and statistical techniques for building models, evaluating the effects of several variables, and obtaining the values of process variables that produce desirable values of the response. This paper reviews the recent information on the use of RSM in different water and wastewater treatment processes. The theoretical principles and steps for its application are first described. The recent investigations on its application in coagulation-flocculation, adsorption, advanced oxidation processes, electrochemical processes and disinfection are reviewed. The limitations of the methodology are highlighted. Attempts made to improve the RSM by combining it with other modelling techniques are also described. [ABSTRACT FROM AUTHOR]