Disinhibition of excessive volatile fatty acids to improve the efficiency of autothermal thermophilic aerobic sludge digestion by chemical approach

Determination of the optimal dosing time of ferric nitrate on disinhibition of excessive volatile fatty acids in autothermal thermophilic aerobic digestion for sewage sludge

“…The dosage of Fe(NO 3 ) 3 $9H 2 O was 3.16 g per L sludge, which was calculated at the ideal molar ratio of 1 : 3 in order to form Fe(CH 3 COO) 3 to reduce acetic acid of 1500 mg L À1 with the decreased amount of sludge by sampling counted. 7 Dened amounts of sodium hydroxide were added into digesters in order to eliminate the inuence of chemicals additions on pH. The dosing time of the different treatments were 3rd day (T9), 6th (T6), 9th (T9) and 12th (T12), respectively, and the one without Fe(NO 3 ) 3 dosed was designated as the control (T0).…”

“…4 Nevertheless, the concerns about issues of poor dewaterability, foaming, disadvantageously excessive concentrations of ammonia and volatile fatty acids (VFAs) generating in the ATAD process for sewage sludge still existed. [5][6][7] Especially, the super-uous VFAs concentration in ATAD system causing by limited aeration and retention time as well as high waste load have aroused more and more attentions. [8][9][10] Although the VFAs are most important intermediary substances for microorganisms 11 and drawn great interests in applications of producing biodegradable plastics, bioenergy and biological nutrient removal processes, 12 the product inhibition resulted from the accumulation of VFAs should be taken into consideration in acidication process.…”

“…Usage of ferric nitrate was conrmed to be a feasible method to remove the inhibition of excessive VFAs and enhance the efficiency of sludge stabilization in one-stage ATAD process lately. 7 Optimal dosage of ferric nitrate on disinhibition of superuous VFAs in one-stage ATAD system was also denite. 21 However, the proper dosing time of ferric nitrate is not determined until now.…”

Evaluation of the Digestibility of Attached and Suspended Growth Sludge in an Aerobic Digester for a Small Community

“…Aerobic digestion is popular for smaller treatment facilities due to its low investment cost, simpler operation and ease of management and control [17,19,20]. Aerobic digestion is the biochemical oxidative stabilization of waste sludge under endogenous conditions; when there is insufficient external substrate available, heterotrophic microorganisms are added to begin to digest their own cellular mass [3,21]. The aerobic digester works on a similar principle as the activated sludge process [21].…”

The effect of phosphate buffer on improving the performance of autothermal thermophilic aerobic digestion for sewage sludge

“…8,9 Especially, accumulation of volatile fatty acid (VFA) would occur when the sludge digestion started with limitation of dissolved oxygen, which would reduce the pH value of the digestion system and then be unfavourable for the digestion process. 10 Furthermore, the over-produced VFA would also inhibit the dominant microbial population in the one-stage ATAD system.…”