Process Intervention for Water Recovery in Food Manufacture

摘要

A case study has been conducted for the recovery of water from complex wastewater at a soluble coffee manufacturing factory. The study has evaluated separation methods for process intervention based on environmental and economic assessments. Water recovery was identified in two possible wastewater streams at the factory: the overall plant effluent and an intermediate stream before it enters on-site pre-treatment. A novel vibratory field membrane separation was tested at the laboratory scale using real factory wastewater and scaled-up using appropriate design protocols. Recovery of water from the intermediate stream proved the most effective, both environmentally and economically. The full-scale vibratory membrane process recovers 100,000 gallons of water per day that meets specifications for the factory cooling tower. The proposed design reduced the daily well water with draw by 21% and the amount of wastewater discharged from the factory by 28.5%. Annual operating costs were reduced by 22.5% and total life cycle emissions were reduced by 27.8%. These reductions are mainly the result of the reduced volume of wastewater discharged from the factory and the reduced energy requirement of the on-site pre-treatment processes. The vibratory membrane process for water recovery presents favorable economics, even after capital costs are considered. The net present value after 10 years is $485,300, while the payback time is under three years.