Nutrient removal using spent coconut husks

Wastewatermanagement posesmajor environmental and economic problems inmany small island developing states (SIDs), such as Trinidad and Tobago. Conventional wastewater treatment using activated carbon (AC) from charcoal is very costly. However, using spent coconut husks can be a cheap, environmentally friendly alternative source of AC for removing nitrogen and phosphorus in the secondary effluent. This study considered thermal and non-thermal, chemical activation methods to create four different AC treatments. The treatments considered included: virgin AC (thermally activated only) and subsequent acid treatments. Acid treatments were considered as an acidic environment, optimized nitrate and phosphate removal and reduced hydroxyl ion competition. Although all treatments were effectively removed nitrates, virgin AC was ineffective in PO4 3 -P removal when concentrations were less than 10 mg/L. This was probably due to naturally occurring PO4 3 -P leaching from the coconut husk. The differences in removal efficiencies andadsorption capacitieswere not significantly different between treatments. Thermal activation was sufficient to remove NO3 -N and PO4 3 -P greater than 10 mg/L in experiments with batch stock solutions and the secondary effluent. Virgin AC can therefore be used as a potential substitute for conventional AC.