Research On The Limits Of Water Quality Guideline Of Reclaimed Water For Green Land Irrigation

This research is a part of China national 863 project ---Water Quality and SafetyEvaluation of Urban Reclaimed Wastewater for Green Land Irrigation. Green landirrigation is a main aspect of reclaimed water. Effects of reclaimed water for greenland irrigation on growth of turf grasses and public health become more important.Four essential limits of reclaimed water: total dissolved solids (TDS), chlorides,residual chlorine and suspended solids (SS) were acquired by hydroponics andpint-size potted experiments of seedling Festuca arundinacea (TF) and Poa pratensis(KBG). Field experiment results and capabilities of two kinds of turf grasses underreclaimed water stresses were analyzed. Considering safety of reclaimed wastewater,primary public health risk assessment was also analyzed. These offered references tothe establishment of water quality guideline of reclaimed water for green landirrigation in China.Negative correlations were observed between physiological, biochemical index ofKBG and the concentrations of essential values of reclaimed water. The adaptivecapability to stresses of TF increased markedly to a certain extent. The activity ofcatalase of TF reached peak under medium concentration. Water quality of reclaimedwastewater for TF irrigation should be met to the following limits: TDS< 1900mg/L,chlorides < 800 mg/L, residual chlorine< 1.0 mg/L, SS < 30 mg/L;for KBG: TDS <1500 mg/L, chlorides <500 mg/L, residual chlorine< 0.75mg/L, SS< 30 mg/L. In fieldexperiments, irrigation with reclaimed wastewater boosted the growth of TF. However,TDS of reclaimed water affected KBG distinctly after six-month irrigation. Understresses, TF had notable advantage over KBG. The amounts of soil bacteria and fungiincreased significantly compared with that of original soil, which showed thatreclaimed wastewater for green land irrigation promoted the growth of soilmicroorganisms.According to the health risk analysis, the total lifetime carcinogenic risk of bodypoison Mn and NH3 of reclaimed wastewater was about 10^-10.The infection probabilityof Salmonella species was about 10^-5. The heath risk limit ratified by USEPA is 10^-4.Therefore, reclaimed water for green land irrigation in this research could be safe.