A comparative study on the use of activated carbon from rice husk and sugarcane bagasse as a low-cost adsorbent in greywater treatment

Abstract

Treated and untreated wastewater is reused both directly and indirectly in developed and less developed countries. In Uganda, grey water is about 50-80 % of residential waste water and onsite sanitation provisions rarely prioritize greywater management. Hence, it is mainly disposed of in existing stormwater drains and open spaces without treatment causing both long term and short- term harm to animals and plants while also wasting a potential source of reusable grey water if treated. In recent years, low-cost agricultural waste by-products such as sugarcane bagasse, sawdust, coconut husk and many more have been discovered to be used as alternative sources of activated carbon used in waste water treatment. This study was undertaken to create an understanding of the characteristics grey water from a household and also to assess and compare the performance of activated carbon from rice husks and sugarcane bagasse as adsorbents in the removal of impurities in grey water. Both activated carbon from rice husk and sugarcane bagasse were used in two designed filter columns simultaneously in this study to get comparative conclusion on the two materials. The effect of pH, temperature, total solids, turbidity, Biochemical Oxygen Demand, Chemical Oxygen Demand and adsorbent source in removal of pollutants present in grey water was evaluated. The studies show that Rice Husk Activated Carbon (RHAC) is generally more effective than Sugarcane Bagasse Activated Carbon (SBAC) but the difference is not as significant as they possess similar surface characteristics on activation. The removal of pollutants from household grey water was based on the National Environment Management Authority (NEMA) wastewater discharge standards. The COD removal is (kitchen: 47 %; laundry: 86 %; bathroom: 18 %) for RHAC and (kitchen: 83 %; laundry: 81 %; bathroom: 78 %) for SBAC and maximum turbidity removal is 97 % in RHAC and 98 % in SBAC. Bathroom water had the least improvement in BOD with 8 % removal in RHAC column and 14 % removal in SBAC column. For the rest, the removal efficiency of BOD in RHAC column was 43 % for Kitchen and 94 % for Laundry water. For the SBAC column it was 70 % for Kitchen and 18 % for Laundry. The materials are also relatively cheap and available hence Sugarcane Bagasse and Rice Husk conversion to activated carbon minimizing the cost of waste transfer and gives cheap resources for generation of activated carbon. Recommendations, however, have been made to look into increase in the sample size to give a conclusive report on the two materials and to add a tertiary treatment step to further improve the effluent from the filter columns. The activated carbon columns can also be looked at as garden fertilizers instead of just disposing of.