Enhanced efficiency for better wastewater sludge hydrolysis conversion through ultrasonic hydrolytic pretreatment

© 2016 Taiwan Institute of Chemical Engineers The major requirements for accelerating the process of anaerobic digestion and energy production are breaking the structure of waste activated sludge (WAS), and transforming it into a soluble form suitable for biodegradation. This work investigated and analysed a novel bench-scale ultrasonic system for WAS disruption and hydrolysis using ultrasonic homogenization. Different commercial sonoreactors were used at low frequencies under a variety of operating conditions (intensity, density, power, sonication time, and total suspended solids) to evaluate the effects of the equipment on sludge hydrolysis and to generate new insights into the empirical models and mechanisms applicable to the real-world processing of wastewater sludge. A relationship was established between the operating parameters and the experimental data. Results indicated an increase in sonication time or ultrasonic intensity correlated with improved sludge hydrolysis rates, sludge temperature, and reduction rate of volatile solids (33.51%). It also emerged that ultrasonication could effectively accelerate WAS hydrolysis to achieve disintegration within 5–10 min, depending on the ultrasonic intensity. This study also determined multiple alternative parameters to increase the efficiency of sludge treatment and organic matter reduction, and establish the practicality of applying ultrasonics to wastewater sludge pretreatment

A new hybrid sewage treatment system combining a rolled pipe system and membrane bioreactor to improve the biological nitrogen removal efficiency: A pilot study

© 2018 Elsevier Ltd A new hybrid pilot plant configuration based on a modularized rolled pipe system (RPS) combined with a submerged flat sheet membrane bioreactor (MBR) was investigated to enhance the sewage treatment and membrane performance. The system was operated under actual conditions for more than four months, that is, at a constant flow rate of 30 m³/d and with two internal recycling ratios. The results indicate that the hybrid system produces an excellent effluent quality and considerably mitigated membrane fouling. The average concentrations of SS, COD, TN, NH4+-N, NO3−-N, and PO43--P remained below 2.81, 8.29, 8.77, 0.15, 8.17, and 1.49 mg/L, respectively. It was estimated that the periodic chemical cleaning of the membrane could be extended to approximately six months. The MBR and RPS can virtually complete nitrification and denitrification, respectively. The highest average denitrification rate of the RPS is 116.95 mg NO3-N/(g MLVSS d), with a hydraulic retention time of 1.05 h. Therefore, the RPS–MBR hybrid system has potential to improve the sewage treatability. The emerging RPS technique can obtain high rates of denitrification coupled with a compact design, ease of installation, and small footprint

Thermogravimetric study and evolved gas analysis of new microalga using TGA-GC-MS

The growing concerns over the environmental challenges emanating from the use of fossil fuels continue to generate interest in finding competitive and sustainable alternatives. This study presents physicochemical characteristics, thermal decomposition profile and kinetics of a new Botryococcus sp. of microalga isolated from Endau-Rompin, Malaysia. The proximate and ultimate analyses were carried out using standard analytical techniques. Thermogravimetric study was conducted in nitrogen atmosphere using a thermogravimetric analyser coupled with gas chromatography-mass spectrometer. The result revealed that the feedstock has high volatile matter (86.74 wt%) and calorific value of 17.18 MJ/kg. The thermal decomposition of the alga sample proceeded via dehydration, decomposition of extractives, hemicellulose, other carbohydrates and lipid evaporation. The kinetics of the alga sample evaluated using a distributed activation energy model showed that the model sufficiently described the pyrolysis of the feedstock with activation energy of 52.72–159.16 kJ/mol. The chemical composition of the evolved gas revealed high content of hydrocarbons, products of carbohydrate and protein decomposition. This suggests that the alga sample is a good candidate for production of valuable precursors for biofuel processing and production of biochemicals