Vermifilters: a tool for aerobic biological treatment of herbal pharmaceutical wastewater

Herbal pharmaceutical wastewater possesses high chemical oxygen demand (COD) (21,960–26,000 mg/l) and biochemical oxygen demand (BOD) (11,200–15,660 mg/l) and suspended solids (SS) (5,460–7,370 mg/l). It cannot be directly discharged into surface water bodies, due to its highly biodegradable nature. Herbal pharmaceutical wastewater has been treated by using vermifilter, which is an ecosystem consisting of biosoil with bacteria and earthworms producing vermicastings. In the present studies a cost-effective, eco-friendly and sustainable method has been applied for the treatment of herbal pharmaceutical wastewater using earthworms. Studies were carried out at different organic loadings, ranging between 0.8 and 3.2 kg COD/m³day at three different hydraulic loadings of 1, 2 and 4 days. Vermifilters packed with 1:1:1 ratio of soil, sand and vermicast as media matrix along with the twenty adult earthworms in each reactor was used for the experiments. Treated effluent was colour and odour free. Efficient COD/BOD removals in the range of 85.44%–94.48% and 89.77%–96.26% were obtained respectively at 2 days hydraulic retention time (HRT). Heavy metal removals were also observed and no sludge production problem was encountered, only nutrient rich vermicast from the filters were removed and analysed after the experiments. It showed higher manurial value than control in terms of available nitrogen, phosphorus and potassium (NPK) and were in the range of 178.75–278.75 Kg/hectare available nitrogen, 16.128–50.4 kg/hectare of available phosphorus and 19.3–28.6 kg/hectare of available potassium at maximum HRT and at different organic loadings. This paper discusses in detail the feasibility of vermifilters in herbal pharmaceutical wastewater treatment at different organic and hydraulic loadings.