An Eco-Friendly Approach to Purify Reject Water from a Reverse Osmosis Treatment Plant

Abstract

Purifying wastewater rejected from the Reverse Osmosis (RO) treatment plants is one of the challenges faced by industries. Wastewater consists of potential contaminants rejected from the RO treatment, referred as RO reject water. The study focuses phytoremediation technology where aquatic plants are used to absorb contaminants in RO reject water. The water hyacinth (Eichorrnia crassipes) and water lettuce (Pistia stratiotes) were selected as floating aquatic plants. Change in water quality before and after being exposed to plants and phytoaccumulation capacity of plants after eight weeks were investigated in the study. Contaminants of RO reject water were successfully removed by aquatic plants only within first four weeks (phase I). A higher reduction in concentration of total hardness, calcium hardness, alkalinity and ions was identified in the treatment tanks compared to control, filled with RO product. The removal of ions decreased with time within phase I, except for chloride and calcium hardness. Although the removal of total hardness, chloride, iron, magnesium, potassium and sodium in RO reject water was significantly (p < 0.5) greater in treatment tanks after first two weeks, only total hardness, alkalinity, iron and sulphate removal were significantly (p < 0.5) higher with time within phase I. Both aquatic plants accumulated ions in biomass especially with a higher accumulation for magnesium, sodium and potassium. Therefore, the proposed water treatment system can be used to treat RO reject water, with regular harvesting of plants and new replacement at every four weeks to maintain the effectiveness of phytoremediation process.