Unit load value of suspended solids (SS) per head of fattening pig per day is important for designing wastewater water treatment plant. Water quality of wastewater was surveyed at 9 swine farms. Ratios of SS and potassium ion concentration (SS/K⁺) of wastewater samples which BOD/N ratio of from 3 to 4 were 7.7 for 50 percentile, 9.0 for 70 percentile and 10.6 for 90 percentile for raw wastewater. The ratios of wastewater after pretreatment with dewatering machine using polyelectrolyte were 0.83 for 50 percentile, 1.2 for 70 percentile and 2.8 for 90 percentile. Unit load values of SS were estimated by multiplying unit urinal excretion value of potassium 9.2 g/head/day to above SS/K⁺ ratios. The unit load values of raw wastewater calculated were 70.8 g/head/day for 50 percentile, 82.8 g/head/day for 70 percentile and 97.5 g/head/day for 90 percentile. The values of wastewater after the pretreatment were 7.6 g/head/day for 50 percentile, 11.0 g/head/day for 70 percentile and 25.8 g/head/day for 90 percentile.

The effect of freeze-thawing and dehydration on water removal and nutrient changes in high-moisture unutilized raw materials and digestibility were investigated using artificial digestion experiments. In this study, the cut lower portions of asparagus stalks, non-standard potatoes and waste tofu were used as typical unutilized raw materials with a high water content. Four treatments were studied: a control treatment - using the raw materials as received; a dehydration treatment - using a dehydrator; a freeze-thawing treatment - thawing after freezing; and a freeze-thawing dehydration treatment - dehydrating after freezing and thawing. For asparagus, the moisture content and rate of moisture removal after the control (raw materials) and dehydration treatments were not significantly different, but after the freeze-thawing and freeze-thawing dehydration treatments, the moisture content was lower and the rate of moisture removal was higher compared with the control (raw materials) and dehydration treatments. In contrast, the moisture content of the potato and tofu was lowest after the freeze-thawing dehydration treatment, followed in increasing order by the freeze-thawing, dehydration and control (raw materials) treatments, with the rate of moisture removal from highest to lowest being in reverse order. The times required for drying in the freeze-thawing and freeze-thawing dehydration treatments were approximately half those required for the control (raw materials) and dehydration treatments. The contents of crude protein and crude ash in the asparagus and potato decreased in the order of control (raw materials), dehydration, freeze-thawing and freeze-thawing dehydration treatments, with the contents of carbohydrate increasing in both asparagus and potato. The crude fat content of asparagus increased in the order of the control (raw materials), dehydration, freeze-thawing and freeze-thawing dehydration treatments, and decreased in potato. There was no difference in the nutrient contents of tofu between the four treatments. There was no difference in digestibility of crude protein measured by the artificial digestion experiments between asparagus, potato and tofu. The dry matter digestibility of asparagus and potato after the freeze-thawing and freeze-thawing dehydration treatments was lower than that after the control (raw materials) and dehydration treatments. The dry matter digestibility of asparagus and potato after the freeze-thawing and freeze-thawing dehydration treatments was lower than that after the control (raw materials) and dehydration treatments, but there was no difference in tofu between the four treatments. These results suggest that freeze-thawing or freeze-thawing dehydration treatments effectively removed water from the raw materials thus shortening their drying times, although these treatments affected the nutrient content and dry matter digestibility.