Wastewater sludge is rich source of nutrients; collected from different sections of wastewater treatment plant. Because of high proportion of nutrients; sludge can be used in farmlands to enhance soil characteristics1. On the other hand; pollutants present in sludge should be managed properly because mismanagement in this regard can leads towards harsh damages to the environment, human health, animals and plants.
In most of the developing countries procedures like anaerobic digestion, aerobic digestion, chemical treatment, air drying, heat treatment, composting and lagoon fermentation are being used to manage municipal wastewater sludge and converting it into an organic fertilizer. But it requires couple of months and less finance and amenities could lead to contamination of farming land through pathogens. In this regard ATAD system is the most reliable technique to treat municipal wastewater sludge. It is an aerobic procedure to digest sewage treatment plant’s sludge. The ATAD does not require any external energy sources, conducts the digestion process in a very short time and the output product meets the class A sludge standards of US EPA2,3.
In recent investigations;4,5,6 scientists have focused on single-stage ATAD system, whereas the dual-stage ATAD provides the quick adjustment of thermophilic microorganisms. Accordingly, Reza Shokoohi and colleague conducted a research to assess the potential of Autothermal Thermophilic Aerobic Digestion (ATAD) system as one of the low-cost and biocompatible techniques of sludge treatment. In this exopriment, the reactor consisted of two polyethylene tanks with a final capacity of 100 L for each tank. Both tanks with all fittings were installed on a metal frame. The variables of research were temperature, dissolved oxygen, pH, volatile organic compounds, total solids, COD and the number of Ascaris eggs and fecal coliforms per gram of dry matter of the sludge. Scientists measured the temperature hourly and the pH and dissolved oxygen were calculated and controlled twice a day. Moreover, results were analyzed by employing One-way ANNOVA.
Scientists noted increment in temperature of sludge from 11.7-61.2°C by biological reactions. Pathogen organisms were decreased from 80×106 to 503 during 72 hours. After 6 days; pathogens and Ascaris eggs were removed completely. While, reduction in volatile organic compounds 42% and COD 38.3% was observed during six days. Scientists concluded that the performance of ATAD in removing organic compounds from wastewater sludge was effective. Moreover, resulted sludge from stabilization process was suitable for use x as a soil supplement and met the indexes of class A sludge according to EPA’s standards (CFR 40 Part 503).
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17 November, 2019