Abstract:
Water recycling in a sustainable manner is increasingly being practiced for protection of water resources. Greywater generated from households can be readily used for recycling due to enhanced quality of this source compared to sewage. Vacuum membrane distillation (VMD), was selected in this research which comprises of evaporation and condensation processes that mimic the water cycle in nature. Solar energy was embedded into the VMD process to minimise energy consumption from non-renewable energy sources. The hydrophobic membrane assists the vaporization of greywater at lower temperatures by means of vacuum pressure on the permeate side. However, the membrane distillation (MD) process is rarely used for wastewater treatment due to the membrane wetting phenomenon which features the penetration of the feed water through the membrane pores. This phenomenon results from active surfactants present in detergents that reduces the contact angle between feed water and the surface of the hydrophobic membrane. Active surfactants are measured as linear alkylbenzene sulphonate (LAS). The main aim of this paper is to investigate the feasibility of a pre-treatment unit, electro-coagulation (EC), for removal of LAS in greywater. EC was incorporated to overcome the complexity of pore wetting for greywater treatment. A range of current density and circulation rate of EC unit was performed, and the quality of permeate water was monitored. It has been demonstrated that, after only 12 minutes of EC, the level of turbidity, total suspended solids (TSS), chemical oxygen demand (COD), total organic carbon (TOC), total nitrogen (TN), total phosphorous (TP), electrical conductivity and faecal coliforms were reduced by an average 94.4%, 89.9%, 83.8%, 71.0%, 73.1%, 96.1%, 30.2% and 1.32 log, respectively. Finally, the EC unit was combined with the VMD system. Water quality and energy consumption were evaluated to determine the optimised level of current density and circulation rate for EC.