بررسی طبقه بندی و ارزیابی کیفی آب خروجی از حوضچه های اختیاری دوم تصفیه خانه شهر یزد در ارتباط با مصارف مختلف کشاورزی و جنبه های بهداشتی

To Classify and evaluate the quality of treated wastewater in Yazd wastewater treatment plant, samples of wastewater were collected weekly and microbial tests were used to determine fecal coliform (Fe) and nematode egg (NE) number per each sample. Also the concentrations of P04, N02, N03, NH3, S04, Na, Ca, Mg, K, HC03, C03, B, F~ Zn, Cu and Mn irons and the amounts of pH, TSS, TDS, EC, SAR, were measured using standard methods. Results showed that the outflow wastewater is classified as class B based on Word Health Organization (WHO) guidelines. Therefore, it is suitable for irrigation of cereals, industrial and fodder crops, pastures and trees. The most limiting factor for use of this wastewater in agriculture is high concentration of HC03 which causes precipitation of (Ca-Mg) Carbonates in the soil and it will increases SAR and finally decreases the infiltration rate of soil in long time. Based on some general assumptions, the Gypsum Requirement (GR) to alleviate harmful effects of high SARadj level in wastewater is equal to 8.62 ton/ha. High concentration of macro nutrients in the wastewater made it possible to produce industrial and fodder crops such as cotton, barley and halophytes (with careful considerations) and will save the cost of agricultural inputs. Boron toxicity in the wastewater is not a limiting factor. Concentration of Na and CI in the wastewater is less than the toxicity threshold level of these ions for cotton, sunflower, corn, sorghum, safflower, sesamum, etc. Concentration of Fe, Cu, Zn and Mn in the wastewater is below the toxicity levels that are recommended by F AO, so these elements do not cause any ionic toxicity for plants. Generally, because of the suitable quality of treated wastewater, it can be successfully used for irrigation of some crops considering health care and technical recommendations, However, since plant is in direct contact with the soil solution and physiochemical characteristics of soil can affect it, so accurate study of these parameters in the soil is necessary to present more accurate agricultural management method in the wastewater treatment plant.