Evaluation of the effectiveness of pervious concrete in the treatment of greywater.

Abstract

Freshwater shortage affects both developing and industrialized nations due to population growth, urbanization, high water consumption, and climate change. This situation requires interventions to reduce reliance on freshwater. Greywater, a low strength wastewater with various reuse possibilities, can replace freshwater for non portable tasks like crop irrigation. However, using untreated greywater can harm crops due to harmful substances, including salts and pollutants. Effective filtration of greywater impurities is essential, with pervious concrete proposed as a potential treatment solution for contaminated water sources. This study aimed to evaluate the effectiveness of pervious concrete in the treatment of greywater and its subsequent application for irrigation purposes. The research was divided into 3 tests (Batch reactor tests, Column tests, and the laboratory-scale greywater treatment system). Column tests were done to determine the long-term performance of the greywater treatment system. The efficiency of pervious concrete in eliminating pollutants from greywater was compared with that of moringa and activated carbon. Greywater was obtained from a student residence at the University of Mpumalanga. Pervious concrete and moringa seeds were used to conduct batch reactor tests with the greywater. The treated greywater's quality was evaluated using physical, chemical, and microbiological parameters. The electrical conductivity (EC) and total dissolved solids (TDS) in the pervious concrete-treated greywater increased from 45.5 mS/cm to 108.6 mS/cm and 252mg/l to 543 mg/L, respectively. The pH increased from 7.4 to 10.89. Values for pH, EC, and TDS fell within the acceptable ranges for irrigation and wastewater discharge into a water source. E. coli, Biochemical oxygen demand (BOD) and turbidity were also reduced following treatment with pervious concrete to levels below the permissible limits for irrigation use and release of wastewater into a body of water. The values of EC (75.8mS/cm-229.3mS/cm), TDS (379mg/l-1147mg/l), E. coli (1CFU/100ml), turbidity (40NTU-122NTU) and BOD (10mg/l-135mg/l) exceeded the maximum limit recommended when the greywater was treated with moringa. Following treatment with pervious concrete and activated carbon for column tests, the values of pH (10.01), EC (37.9 mS/cm), and TDS (190 mg/l) were in the applicable restrictions for the discharge of wastewater after treatment with pervious concrete. BOD (<11), Turbidity (1.1 NTU), and E. coli (<1 CFU) were reduced following treatment with pervious concrete. TDS and EC values exceeded the maximum limit recommended after treatment with activated carbon. Pervious concrete achieved a 90.9% Mg removal, 83% ortho phosphate removal and 79.1% Fe removal, while activated carbon achieved a 77% Ca removal and 90.9% Mg removal. Therefore, the results show that pervious concrete can be a simple and efficient method that can be adopted for treating greywater for use in agriculture and replenishing water resources.