Abstract:

The pollutants in raw sewage, once-treated and double-treated ground water were tested and biological effects on floating lettuce were analyzed to alleviate pollution issue of surface water in vegetable garden, which resulted in irrigation water under proof. The results showed, the content of suspended solids in raw sewage was 78 mg/L, exceeding the warning level, BOD5, COD three fecal coliforms were 11.5 mg/L, 42 mg/L and 700 /100 mL, respectively, failing to meet the clean water standard. Most of pollutants were reduced to some extent after once or double treated. The suspended solid amount was decreased to 13 mg/L and 10 mg/L, respectively, qualified for agronomical irrigation. BOD5 and COD, fecal coliforms were up to scratch. Once-treated water and tap water were used in lettuce floating transplant system to test its biological effects on vegetable growth. Results demonstrated that compared with tap water treatment, no biological abnormal phenomenon on development and yield was observed, indicating once-treated water can be used in vegetable irrigation.