Effects of Sludge Concentration and Disintegration/Solubilization Pretreatment Methods on Increasing Anaerobic Biodegradation Efficiency and Biogas Production

It is urgent to determine suitable municipal sludge treatment solutions to simultaneously minimize the environmental negative impacts and achieve sustainable energy benefits. In this study, different sludge pretreatment techniques were applied and investigated to enhance the sludge solubility and, subsequently, facilitate the anaerobic biodegradation performance of the mixed sludge under different sludge concentrations and pretreatment techniques. The sludge characteristics before and after pretreatment and batch experiments of anaerobic digestion of sludge samples under different conditions were analyzed and discussed. The results showed that the mechanical pretreatment method, alone and in combination with low-temperature heat treatment, significantly improved the sludge solubility, with the highest solubility at 39.23%. The maximum biomethane yield achieved was 0.43 m3/kg after 10 d of anaerobic digestion of a 3% sludge sample subjected to mechanical and thermal pretreatment prior to anaerobic biodegradation. In comparison, it took more than 28 d to achieve the same biomethane production with the unpretreated sludge sample. Mechanical pretreatment and subsequent heat treatment showed a high ability to dissolve sludge and, subsequently, accelerate anaerobic digestion, thereby providing promising prospects for increasing the treatment capacity of existing and new sludge treatment plants.

The effect of free nitrous acid pretreatment on the anaerobic digestibility of thickened waste activated sludge

Sludge pretreatment technologies as an avenue to improve solids handling in a WWTP has gained attention and significant research efforts are being directed towards studying several available techniques. The use of FNA as a chemical pretreatment for the AD has shown the potential to enhance the hydrolysis stage by releasing the internal organic matter of TWAS via its biocidal action. The effect of FNA on improving the biodegradability of TWAS was investigated in this thesis. The effect of the FNA on the TWAS characteristics and the methane production in batch tests was first studied. The optimum FNA dose was determined from the batch tests based on both solubilization and methane yields and then tested in a semi-continuous flow system. As the semi-continuous flow system failed when the optimum FNA dose obtained from the batch study was used, another set of semi-continuous flow experiments were conducted using different FNA doses

The effect of free nitrous acid pretreatment on the anaerobic digestibility of thickened waste activated sludge

Sludge pretreatment technologies as an avenue to improve solids handling in a WWTP has gained attention and significant research efforts are being directed towards studying several available techniques. The use of FNA as a chemical pretreatment for the AD has shown the potential to enhance the hydrolysis stage by releasing the internal organic matter of TWAS via its biocidal action. The effect of FNA on improving the biodegradability of TWAS was investigated in this thesis. The effect of the FNA on the TWAS characteristics and the methane production in batch tests was first studied. The optimum FNA dose was determined from the batch tests based on both solubilization and methane yields and then tested in a semi-continuous flow system. As the semi-continuous flow system failed when the optimum FNA dose obtained from the batch study was used, another set of semi-continuous flow experiments were conducted using different FNA doses

Dissolved organic matter byproducts from combined low-level alkaline and mechanical treatment of sludge: species, and their bioavailability

Low-level alkalinity (pH 9–10) coupled with ultrasonic or mechanical cutting with different energy input for obtaining carbon sources were tested for sludge pretreatment process before anaerobic sludge digestion. The differences between the primary sludge (PS) and waste activated sludge (WAS)-derived DOM species were evaluated for their bioavailability and affinity (in the form of amino acids) to the bio-nutrient removal (BNR) biomass. Soluble microbial by-product-like substances as the predominant DOM components in the raw PS and WAS increased by 23 and 22%, respectively, after low-level alkaline treatment (pH 9–10) and ultrasonication. In addition, the protein components were degraded further as free amino acids (FAAs). The sludge-derived aspartate, glutamate, followed by arginine were most commonly used FAAs by the BNR biomass. The pattern of recovering this special sludge-derived carbon source to enhance P removal and recovery in the BNR process is depicted.