ABSTRACT
Introduction: One of the methods for disposal of sludge is its usage as fertilizer on agricultural. The purpose of this study was to analyze the possibility in the application of sludge to agricultural, according to environmental standards
Methods: This descriptive-analytic study was conducted for 12 months on dried sludge wastewater treatment plant in Yazd. Monthly sampling and tests were performed on samples in all four seasons of winter, spring, summer, and fall, thus, totally 24 samples were collected. The physical, chemical, fertilizer values, microbiological characteristics, and metal of the sludge were measured and their mean were compared with EPA standards
Results: The results showed that the mean of pH, TS, moisture, and organic material in the sludge were 6.58%, 58.31%, 11.37 %, 33.09 % respectively and they were in a normal range. The mean of carbon, nitrogen, phosphorus, sodium and potassium, were 61.5%, 5.47%, 4.34%, 0.43%, 0.42%, respectively which only sodium was in the range and the rest exceeded it. The mean of coliform and fecal coliform were 15062 and 2655[MPN/g], respectively and the mean of parasite eggs per 4 g/dry sludge in the four seasons was 3. The mean of metals, namely lead, iron, zinc, manganese, and copper were 19.64, 47.57, 864.23, 89.06, and 146.26 mg / kg.dry solid, respectively
Conclusion: Results of the study showed that the sludge wastewater treatment in Yazd was in the range of EPA standards for Class B
ABSTRACT
Background: Investigating the performance of naturally operated treatment plants may be due to the fact that they cannot be operated as desired, or that they should be modified to achieve good performance e.g. for nutrients removal. The advantage of kinetic coefficient determination is that the model can be adjusted to fit data and then used for analyzing alternatives to improve the process. This study investigates the efficiency of subsurface artificial wetland and determines its kinetic coefficients for nutrient removal
Methods: The present study investigated the kinetics of biological reactions that occurred in subsurface wetland to remove wastewater nutrient. Samples were taken from 3 locations of wetlands for 6 months. The nutrient content was determined through measuring Total Kjehldahl Nitrogen [TKN], ammonium, nitrate, and phosphate values
Results: Average levels for TKN, ammonium, nitrate, and phosphate in effluent of control wetland were 41.15, 23.59, 1.735, and 6.43 mg/L, and in wetland with reeds were 28.91, 19.99, 1.49 and 5.63 mg/L, respectively. First-order, second-order, and Stover-Kincannon models were applied and analyzed using statistical parameters obtained from the models [U[max], K[B]]
Conclusion: The nutrients removal at Yazd wastewater treatment plant was remarkable, and the presence of reeds in wetland beds was not very efficient in improving system performance. Other more efficient plants are suggested to be evaluated in the system. Stover-Kincannon kinetic model provided predictions having the closest relationship with actual data obtained from the field