Anaerobic digestion of thermal pre-treated sludge at different solids concentrations – Computation of mass-energy balance and greenhouse gas emissions

Anaerobic digestion of ultrasonicated sludge at different solids concentrations - Computation of mass-energy balance and greenhouse gas emissions

This review summarizes the effect of high- and low-temperature thermal pretreatment (TPT) on sludge dewaterability, anaerobic digestion (AD), and biogas production efficiencies. The AD of the TPT sludge has demonstrated the following observations: reduced sludge retention time, increased biogas generation, higher organics degradation, improved dewaterability, and lower digester volume than the conventional AD of sludge. Energy balance of the TPT process was energetically self-sustainable and produced surplus energy at solids concentration greater than 3%. Net energy and energy ratio of TPT and AD revealed that net energy and energy ratio are increased with increase in total solids concentration.

Fenton pre-treatment of secondary sludge to enhance anaerobic digestion: Energy balance and greenhouse gas emissions

Effects of thermal and thermal-alkaline pretreatments on continuous anaerobic sludge digestion: Performance, energy balance and, enhancement mechanism

Predicting the apparent viscosity and yield stress of digested and secondary sludge mixtures

Biosolid Management Options in Cassava Starch Industries of Thailand: Present Practice and Future Possibilities

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Greenhouse gas emissions and energy assessment of modified diesohol using cashew nut shell liquid and biodiesel as additives

Untangling the effect of solids content on thermal-alkali pre-treatment and anaerobic digestion of sludge

Global warming potential and energy analysis of second generation ethanol production from rice straw in India

Greenhouse gas emissions in sludge ultrasonication followed by anaerobic digestion processes

Aerobic composting and anaerobic digestion of pulp and paper mill sludges

The feasibility of aerobic vessel composting and anaerobic digestion for the treatment of pulp and paper mill sludges were studied. The composting studies made use of primary and secondary sludge from a de-inking and paper mill. In six parallely aerated 500 1 vessels with various carbon : nitrogen (C:N) -ratios, the most optimal performance was obtained with C:N -ratios of c. 22–35, while higher and lower ratios delayed the temperature increase. With the optimal ratios, the thermophilic stage was reached within 36 h, and the stage lasted for about seven days. In the scale-up study (18 m3 compost vessel), the thermophilic stage was reached within 24 h. An effective dehydratation of the mass was obtained as the total solids (TS) content of the compost increased from 31.3– to 63.8– within 21 days. The anaerobic digestion of pulp and paper mill sludges was studied using two mesophilic 5 1 digesters, their feed sludges consisting of a mixture of municipal sewage sludge and primary and secondary sludge from a pulp and paper mill. With this feed mixture and with a loading rate of about 1.0 kg volatile solids (VS)/m3d a removal of about 27 to 40– VS and methane production of about 180 1/kgVSadded feed sludge were achieved during the 80 d study period. The study showed that pulp and paper mill sludges are amenable to both aerobic composting and anaerobic digestion.

The present study aimed at investigating the effect of thermal pretreatment of sludge at 70 degrees C on the anaerobic degradation of three commonly found phthalic acid esters (PAE): di-ethyl phthalate (DEP), di-butyl phthalate (DBP), and di-ethylhexyl phthalate (DEHP). Also, the enzymatic treatment at 28 degrees C with a commercial lipase was studied as a way to enhance PAE removal. Pretreatment at 70 degrees C of the sludge containing PAE negatively influenced the anaerobic biodegradability of phthalate esters at 37 degrees C. The observed reduction of PAE biodegradation rates after the thermal pretreatment was found to be proportional to the PAE solubility in water: the higher the solubility, the higher the percentage of the reduction (DEP > DBP > DEHP). PAE were slowly degraded during the pretreatment at 70 degrees C, yet this was probably due to physicochemical reactions than to microbial/biological activity. Therefore, thermal pretreatment of sludge containing PAE should be either avoided or combined with a treatment step focusing on PAE reduction. On the other hand, enzymatic treatment was very efficient in the removal of PAE. The enzymatic degradation of DBP, DEP, and DEHP could be one to two orders of magnitude faster than under normal mesophilic anaerobic conditions. Moreover, the enzymatic treatment resulted in the shortest half-life of DEHP in sludge reported so far. Our study further showed that enzymatic treatment with lipases can be applied to raw sludge and its efficiency does not depend on the solids concentration.

Performance of a forward osmotic membrane bioreactor for anaerobic digestion of waste sludge with increasing solid concentration