Coconut husks as a packing media in anaerobic filters for the treatment of septic tank effluent in Tonga

Abstract

Septic tanks can become overloaded overtime due to increases in the size of households or the build-up of sludge. This results in the wastewater spending less time within the tank and therefore a reduced level of treatment. One solution to enhance treatment is to add an anerobic filter after the existing septic tank. The anaerobic filter requires media for the establishment of a biofilm and the use of coconut husks were identified as a possibility due to their abundance. Both green and brown coconut husks were imported from Tonga and tested in laboratory scale anerobic filters treating synthetic wastewater. The treatment performance was monitored in terms of the chemical oxygen demand (COD) which is a measure of organic strength. There was also potential for organic material to leach out of the coconut husks so additional testing was done to evaluate this. It was found that four times more COD was leached from the green coconut husks showing that brown coconut husks were the better choice. The brown coconut husk reactor reduced the COD concentration by 49%. This study has indicated that there is value in examining the feasibility of implementing an anaerobic filter using brown coconut husks to enhance wastewater treatment from septic tanks. Further research should focus on examining whether any nutrients are released from the husk and then practical considerations such as the scale needed for a household and maintenance requirements.