Computer-aided process design, economic evaluation and environmental impact assessment for treatment of cheese whey wastewater

Efficient software was used for the comparison of five alternative scenarios for the treatment of cheese whey wastewater resulting from a Cheddar cheese factory. Scenario 1 deals with a cheese whey wastewater treatment plant that produces butter, whey protein concentrate and food-grade ethanol. In scenario 2 the butter-making section is similar to the basic process (scenario 1) with some differences in the concentration of whey proteins and in the removal of residual minerals from water. In scenario 3 the plant produces Manouri (a type of cream cheese) instead of butter. In scenario 4 the plant produces two types of whey protein concentrate (WPC), namely, a rich in whey lipids (WPC 2) and the other a highly purified protein concentrate possessing improved functional properties (WPC 1). In addition a process that produces pure lactose has replaced the ethanol section. In scenario 5 the plant produces butter, whey protein isolate (WPI) containing 95% protein and hydrolyzed-isomerized whey permeate syrup (HIPS). The economic comparison has shown that scenario 3 is the most profitable due to its high net present value (NPV) and low payback period as well as to its low production rate (40% of the full production rate) at the breakeven point. The environmental impact assessment demonstrated that scenario 4 is more environmentally friendly than the others due to the absence of biomass in the effluent.

The economic comparison of the five proposed scenarios for the utilization of cheese whey resulting from a 214 tons/d capacity of Cheddar cheese has shown that scenario 3 is more profitable than the others due to its low production rate (40% of the full production rate), the high net present value and the low payback period. It is worthwhile mentioning that the economic comparison was based on the computer output of the evaluation report of SuperPro Designer and not to other additional information, such as fines for environmental damages. The environmental impact assessment demonstrated that scenario 4 is more environmentally friendly in comparison with the other plants due to the negligible quantities of nitrogen and solids in the effluent. The amount of biomass (yeast) that is rejected to the environment is responsible for the high rates of total Kjeldahl nitrogen (TKN), ammonia nitrogen (NH3) and total solids (TS) in the effluent of the plants. The values for the environmental parameters (COD, BOD, etc.) are quite close for the three technological proposals (scenarios 1, 2 and 3) and only the effluent with TDS differs considerably. Furthermore the high amounts of solid wastes distinguish the fifth scenario from the others. The overall evaluation approach resulted in two technological proposals (scenarios 3 and 4) that outweigh the others with regard to environmental and profit factors. Nevertheless, the best choice will be determined by other factors such as the national regulations and the financial demands of the investors. The economic comparison was based on the computer output of the economic evaluation report of SuperPro Designer and not to other additional information, such as fines for environmental damages.