3.2. Cost recovery period
Calculated SWU shows the benefit gained by introducing the oil-water separation technology. The difference
between output value (the benefit calculated by SWU) and input value (the cost invested for the wastewater
treatment facilities and oil-water separation technology) indicates the value produced or wasted by introducing oilwater
separation technology into wastewater treatment system. Then, using SWU, and initial and running cost of
facilities, the value produced per month can be clarified and the cost recovery period can be calculated. If the cost
recovery period is shorter than the lifetime of facilities, introducing oil-water separation technology is economically
feasible.
In the case of the food processing factory, the cost of wastewater treatment facilities and oil-water separation
technology was shown in Table. 1. Moreover, the result of SWU simulation of the food processing factory (the
separation ability 99.70%, the oil mixing ratio of wastewater 10%) was calculated as 8377.9 JPY/h. Under the
working condition of 20 days per month and 8 hours per day, SWU was calculated as 1,340,464 JPY/month.
Excluded the running cost, the surplus was used for the cost recovery of the initial cost.
The cost recovery period for the initial cost of the oil-water separation equipment 13 million JPY was calculated
as 12.6 month (1 year) and the cost recovery period for the initial cost of the wastewater treatment facilities 60
million JPY was calculated as 58.1 month (4.8 years). Totally, it took 70.7 month (5.8 years) to recover the initial
cost of the wastewater treatment facilities and the oil-water separation equipment.
The lifetime of the oil-ware separation equipment was not revealed in this research. It was indicated that after
recovering the initial cost (5.8 years), the surplus which was used for recovering the initial cost was gained as profit.