Annexure - VI EFFLUENT TREATMENT FOR A CASHEW NUT PROCESSING INDUSTRY
1.0
PREAMBLE
As part of MINAS, CPCB desires to establish norms for wastewater treatment of a typical Cashew Nut processing discharging 200 litre/day at a BOD of 5000 mg/l, COD of 10000 mg/l and Oil & Grease (Extractable, mostly in the form of phenolics compounds) at 2000 mg/l. Obviously, wastewater of this magnitude can not be handled in conventional manner. The suggested Mini ETP reclamation system alternatives, viz, a) Pre-engineered Rotating Biological Contactor and b) Sequential Batch Reactor are easy to operate and maintain, complying to BETNEEC (Best Environmental Technology Not Entailing Excessive Cost) approach. 2.0
PLANT DIAGNOSIS – EVOLUTION OF INPUT DATA
The Cashew Nut processing unit involves deployment of employees, food preparation or prepared food supply in the complex etc, besides generating process wastewater. Domestic Effluent: The entire water used for WC/Urinal, Dining Hall will re-appear as sewage. @ 45 LPCD and allowing 10% floating population the total sewage flow can be estimated for domestic sewage/sullage, knowing the connected population. Trade Effluent: 200 litre/day @ BOD of 5000 mg/l, equivalent to 22 to 25 Population Equivalent. The required treatment system: A mini Effluent treatment with reclamation mode, so that the treated water can be used for Landscaping (to be applied @ 2.5 to 3.5 litre/sqm/day) and the WC/Urinal wastewater after septic tank or raw wastewater as such be mixed with trade effluent for combined treatment. Drainage and other Infrastructure: The plot allotted for the factory has to have an organized drainage system around and water requirement has to be met from ground water resources or through procurement strategy. The sewer network and common collection system will result in terminal manhole at some invert level. Based on this, the post pumping or gravity flow requirement has to be decided. 3.0
INNOVATIVE MINI ETP RECLAMATION SYSTEM EVOLVED FOR SITE SPECIFIC SITUATION
DESIGN FORMULATION Flow : The design wastewater flow will be 200 litre/day BOD : The wastewater will be collected in a terminal collection cum buffer tank. At 5000 mg/l, the BOD load is 1000 grams/day. Being a reclamation project, the entire wastewater has to be collected in a central place and treated to meet the good quality BOD norm of < 20 mg/l. The wastewater will be treated to render the following treated effluent quality:
