Abstract
The present study aims to optimize the operational conditions in surface water coagulation/flocculation and sedimentation step, besides evaluating the association between seeds ofMoringa oleiferaLam. (M. oleifera) and the synthetic coagulant aluminium sulphate for surface water treatment. The assays were performed in Jar Test using surface water from Pirapó River basin, Maringá, PR. It was observed that the operational conditions affect the coagulation/flocculation and sedimentation process efficiency. Optimal operational conditions for coagulants association are as follows: rapid mixing velocity (RMV) of 105 rpm, rapid mixing times (RMT) of 1 min, slow mixing velocity (SMV) of 30 rpm, slow mixing times (SMT) of 15 min, and sedimentation time (ST) of 15 min; this enables an improvement in the process, contributing to a reduction in synthetic coagulant aluminium sulphate demand of up to 30%, combined with an increase inM. oleiferadosage, not affecting the coagulation/flocculation and sedimentation process efficiency, considering the water pH range between 7 and 9.
Highlights
Millions of people are exposed to dangerous levels of chemical pollutants and biological contaminants in drinking water due to the inadequate handling of urban population and industrial or agricultural wastewaters [1]
Aluminium sulphate (Al2 (SO4 )3 ⋅18H2 O) stands out as the most used synthetic coagulant in Brazil when it comes to water treatment of public supplies as a result of its high efficiency in suspended solids removal and low cost [3]
Its effect is strongly dependent on pH, especially in the range from 5.5 to 8 [4], and at the end of the treatment there is the possibility of a high concentration of residual aluminium remaining in water [5], which can be associated with the acceleration of degenerative processes of Alzheimer’s disease [6,7,8]
Summary
Millions of people are exposed to dangerous levels of chemical pollutants and biological contaminants in drinking water due to the inadequate handling of urban population and industrial or agricultural wastewaters [1]. It is necessary to carry out physical, chemical, and/or microbiological processes in order to remove the impurities present in water and coagulants have been widely used in this way in conventional processes of water treatment [2]. Aluminium sulphate (Al2 (SO4 )3 ⋅18H2 O) stands out as the most used synthetic coagulant in Brazil when it comes to water treatment of public supplies as a result of its high efficiency in suspended solids removal and low cost [3]. There is the problem of the reaction between aluminium and the natural alkalinity present in water, which leads to a pH reduction [9]. It is interesting to propose alternatives to reduce the quantity of the synthetic coagulant, such as the utilization of natural coagulants in water treatment
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