This study aimed at the application conditions of environmental materials in sweet potato starch wastewater by hydrolysis acidification process. The removal rates of COD and soluble protein were investigated to find suitable natural setting time, the quantity of acidic steeping liquor and pH. The results showed that traditional fermentation not only consumes time but also scarcely removal efficiency in short time. 40% acidic steeping liquor was added as an optimum dosage for effective treatment. In addition, the effort of pH (3.0-9.0) on the hydrolysis acidification of wastewater was investigated. The removal rates of COD and soluble protein reached 26.9% and 76.3% respectively at pH4.0. Therefore, pH was adjusted to isoelectric point that can effectively reduce the burden of subsequent wastewater treatment.

Under the static condition, researching zeolite 4A to the chromium ion's adsorption characteristic, discussing the influence of different adsorption factors. The results indicated that: When the wastewater temperature was 30°C, at pH 3-4,adsorbed 30min,dosing 3g/L of zeolite 4A adsorption chromic wastewater(100mg/L), the chromium ion elimination rate may reached above 99%. At the same time, the zeolite 4A conforms to Langmuir and the Freundlich isotherm to the chromium ion's adsorption, the correlation coefficient respectively was 0.9997 and 0.9753, obtained the zeolite 4A to the chromium ion saturated adsorptive capacity was 50.25mg/L.Obviously, zeolite 4A as a new inorganic ions exchange material for the treatment of chromic wastewater, has the broad prospects for development.

This study aimed at, pre-treatment of sweet potato starch wastewater and acquisition the application conditions of environmental materials though coagulation precipitation. The removal rates of COD and turbidity were investigated by process to find kind and quantity of suitable coagulant, quantity of coagulate aids, pH and setting time. The results showed that poly aluminum ferric chloride (PAFC) was chosen as an optimum coagulant for effective treatment. The optimal coagulation precipitation conditions were determined as follows: pH8, dosage of PAFC 1200mg/l, PAM100mg/l, sedimentation time 30 min. At optimum conditions of coagulation precipitation stages, the removal rate of COD and turbidity reached 25.8% and 67.5%, respectively. Therefore, coagulation process reduced the burden of subsequent wastewater treating.

In order to improve sweet potato starch production technique of small-scale plant and decrease the discharge of pollutant in production wastewater, the yielding water of starch production was treated efficiently by the new environment materials and technology. Subsequently, the treated wastewater was circulated and reused in starch producing process. The results showed that the quantity of starch wastewater was decreased. When the recycle ratio is below 30%, the starch quality was hardly influenced. When the recycle ratio is above 50%, the pollutants in wastewater increased significantly, starch yield dropped nearly to 50% and starch acidity exceeded the national standard. Finally, wastewater reuse ratio should be controlled below 30%.