Treatment of domestic wastewater using the combination of porous concrete and phytoremediation for irrigation

Abstract

Phytoremediation method, in combination with porous concrete and some additives, has been examined in order to reduce the contamination of unconventional water resources. This treatment system is economically cost-effective and easy to apply, compared to other treatment methods. The current study was focused on evaluating the effects of arrangement of vetiver grass and porous concrete specimens (four types of grass-specimens arrangements), vetiver grass layout on polystyrene sheets (5 × 5 and 10 × 10 cm spacing), porous concrete mixture (basic design as control, basic design + 5% zeolite, basic design + 10% zeolite, basic design + 5% pumice), temperature of the test room (10 ± 2, 20 ± 2 and 30 ± 2 °C), type of the unconventional water (domestic wastewater effluent and urban runoff) and Portland cement type (2 and 5) on the reduction of biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), and fecal coliforms. Taguchi method (robust design) and Qualitek-4 software were used to optimize the combination of aforementioned factors. Results indicated that temperature was the most effective parameter on reducing the BOD, COD, and fecal coliforms. The vetiver grass layout on the polystyrene sheets and porous concrete mixture design were more effective than vetiver grass-porous concrete arrangement. Effect of vetiver grass roots was significant in reducing the TSS content. The cement type had minimum impact on reducing the qualitative parameters of the wastewater samples. Based on the results, combination of 10 × 10 cm spacing of vetiver grass on polystyrene sheets, third type of vetiver grass-porous concrete arrangement, porous concrete mixture with 10% zeolite, Portland cement Type 2, and room temperature of 30 ± 2 °C was the best for improving the quality of wastewater effluent as compared to urban runoff. The treated effluents can be used with caution for urban green spaces or irrigation purposes, and the difficulties of the proposed combined system should be taken into consideration.