Effect of Sulphate on Fermentative Sludge Hydrolysis Cum Biodegradation of Waste Activated Sludge
01 Jan 2019-pp 639-650
TL;DR: In this paper, the effect of fermentative sludge hydrolysis cum biodegradation of WAS in the presence and in the absence of sulphate was investigated in a sequential batch reactor (SBR) at room temperature (31-33 °C) in an orbital shaker at 120 ± 2 rpm with cycle time of 7 days.
Abstract: The waste activated sludge (WAS) from the activated sludge process needs an appropriate sustainable sludge treatment and management. The sludge treatment and the management cost around 60% of the capital cost and 50–60% of the operating cost of a wastewater treatment plant. Anaerobic digestion is the dominant process for the sludge reduction and/or stabilization of WAS. Though many physico-chemical techniques are developed as a pre-treatment to enhance the hydrolysis of sludge prior to biomethanation, most of the techniques are very expensive and therefore not practical to apply in the field scale. This work shows the effect of fermentative sludge hydrolysis cum biodegradation of WAS in the presence and in the absence of sulphate. Sequencing batch reactor (SBR) operation at room temperature (31–33 °C) in an orbital shaker at 120 ± 2 rpm with cycle time of 7 days was adopted to compare the performance of fermentation in the presence and in the absence of sulphate. The fermentation in the absence of sulphate was conducted in the presence of externally added COD (sucrose) varied as 500, 1000, 1500 and 2000 (in mg/L). The sulphidogenesis reactors were maintained at a COD/SO42− ratio of 1.0 and varied the concentration of both sulphate and COD as 500, 1000, 1500 and 2000 (in mg/L). An abiotic control was also maintained to evaluate the processes. The percentage sludge reduction varied between 27 and 98%, where the maximum reduction of about 96% was observed in the fermentative reactor in the presence of 500 mg/L of COD, whereas 98% solid reduction was observed in the sulphidogenesis reactor at 2000 mg/L of COD and sulphate. The other parameters such as pH, oxidation–reduction potential (ORP), VFA, alkalinity, soluble and total COD, and turbidity were analysed, and the results are discussed in the paper.
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TL;DR: In this paper, the authors evaluated the effect of three different rates of municipal biosolids produced in Qatar on plant characteristics and soil texture and its potential impacts on groundwater, including electrical conductivity, pH, macro and micronutrients and heavy metals.
Abstract: This study was conducted to evaluate the effect of three different rates of municipal biosolids produced in Qatar on plant characteristics and soil texture and its potential impacts on groundwater. Petunia atkinsiana, was used in this study. The experiment took place in a greenhouse in pots with soil mixed with 0, 3, 5, and 7 kg/m2 biosolids. Pelletized class A biosolids from the Doha North Sewage Treatment Plant were used. Results revealed significant differences in all measured parameters, which were affected by biosolid treatments compared to the control treatment. Electrical conductivity, pH, macro and micronutrients and heavy metals were significantly affected by biosolid treatments. The comparison of the discovered levels against the international acceptable ceilings of pollutants indicated the advantages of utilizing class A biosolids, as they were well below the international acceptable levels and showed the best test rates, indicating that the product is a sustainable and efficient organic fertilizer for ornamental plants. Furthermore, the results highlight no potential significant impacts on groundwater due to trace presence of heavy metals, owing to the nature of deep groundwater in Qatar and the usage of modern irrigation devices that fulfil the exact needs of plants in a harsh climate and high evaporation rate.
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