WASTEWATER TREATMENT IN DESICCATED COCONUT INDUSTRY
DOI:
https://doi.org/10.31357/fesympo.v0i0.1613Abstract
Coconut products are the second largest agricultural export product in Sri-Lanka after tea.Desiccated Coconut (DC) accounts for almost 40010of the total export revenues from coconutproducts. Sri Lanka is the second largest producer of desiccated coconut in the world (after thePhilippines) and the production is 3tillgrowing rapidly. Sri Lanka is estimated to produce 50,000tonnes of desiccated coconut per year accounting for 40% of the world production
Most of coconut plantations and its related industries are located in the triangle of the three citiesof Colombo, Kurunegala and Puttalam, Presently there are 64 DC mills in operation, of whicharound 50 are large-scale factories, processing over 100,000 coconuts per day. The remainingmills are medium scale; processing around 50,000 coconuts per day.
mills are medium scale; processing around 50,000 coconuts per day.Some of the existing DC industries significantly contribute to the deterioration of the quality ofthe environment. According to the 1993 report of Central Environmental Authority (CEA),desiccated coconut industry is the third major water polluter in Sri Lanka after natural rubberindustry and concentrated latex industry.
One coconut gives approximately 0.15 I of coconut water. Combined with wash water andsterilizing water, a factory processing 50,000 nuts/day discharges about 50m3 of wastewater perday. A characteristic waste water cocktail from a DC mill comprises COD 8000mgll, BOD4000mg/L, SS 300mg/l, Nitrogen (nitrate, nitrite and ammonia) 50mgll and PhosphorousIOmg/1.ThepH value is around 5.0.Most factories discharge their untreated or poorly treatedeffluent to general watercourses .creating significant pollution and problems for downstreamusers.
In some DC mills some treatment is attempted, using physical treatment methods like screeningand oil separation. Since the strength of the waste stream is very high, physical treatment aloneis not enough. Chemical treatment methods will cerate large amounts of sludge, which also hasto be treated. Therefore the possibility of biological treatment was investigated and an aerobicbacteria mix named EM (effectivemicroorganisms) was selected.
The treatment process sequence identified in this study is screening, oil separation, aeration,sedimentation, secondary aeration, secondary sedimentation and filtration. EM is added to bothaeration tanks. The optimum volumes of EM to be added to the tanks are currently underinvestigation. Batch testing with EM shows 75% COD reduction by one aerator. With twoaerators in tandem, it can reduce the COD values to comply with the Sri Lankan Standard forDischarge of Industrial Effluents in to Inland Surface Waters (1990). The treatment processdeveloped in this research overcomes the odour problem. To ensure the effluent will not havefree EM, it is chlorinated before discharge into the polishing filter for the final treatment step.
