The
electrochemical (EC) combined with hypochlorite (ClO–) pretreatment has been proven to be effective in improving disintegration
of waste-activated sludge (WAS) and enhancing anaerobic digestion
recently. The ClO– dosage had a significant impact
on the performance of WAS solubilization and biogas production in
terms of the disintegration degree (DDCOD), release of
proteins (PNs) and polysaccharides (PSs), soluble nitrogen and phosphate,
and subsequent anaerobic digestion. The results showed that a higher
ClO– dosage was favorable to WAS solubilization
and EC–ClO– pretreatment was able to rupture
the floc structure and break cells apart. According to batch anaerobic
digestion tests, the optimum ClO– dosage for EC–ClO– pretreatment was 0.6% (v/v), with up to 61.1% higher
methane production compared to the unpretreated sludge after mesophilic
anaerobic digestion for 40 days. Model-based analysis suggested that
EC–ClO– pretreatment could enhance the hydrolysis
process as well as methane potential. Moreover, EC–ClO– pretreatment at the ClO– dosage
of 0.6% was economically feasible based on the economic evaluation.
Waste activated sludge (WAS) requires a long digestion time because of a rate-limiting hydrolysis step - the first phase of anaerobic digestion (AD). Pretreatment can be used prior to AD to facilitate the hydrolysis step and improve the efficiency of WAS digestion. This study evaluated a novel application of electrochemical (EC) technology employed as the pretreatment method prior to AD of WAS, focusing on the effect of process conditions on sludge disintegration and subsequent AD process. A superior process condition of EC pretreatment was obtained by reaction time of 30 min, electrolysis voltage of 20 V, and electrode distance of 5 cm, under which the disintegration degree of WAS ranged between 9.02% and 9.72%. In the subsequent batch AD tests, 206 mL/g volatile solid (VS) methane production in EC pretreated sludge was obtained, which was 20.47% higher than that of unpretreated sludge. The AD time was 19 days shorter for EC pretreated sludge compared to the unpretreated sludge. Additionally, the EC + AD reactor achieved 41.84% of VS removal at the end of AD. The analysis of energy consumption showed that EC pretreatment could be effective in enhancing sludge AD with reduced energy consumption when compared to other pretreatment methods.
In this article, the stabilisation problem is considered for a wireless networked control system. A new model is constructed by integrating the wireless network protocols in IEEE802.11 with control systems. All the possible delays and dropouts are considered in the new model for the packets to be transmitted on both the sensor-to-controller side and the controller-to-actuator side of the WNCS structure. A linear state feedback controller is designed to stabilise the model. The results are given in the form of linear matrix inequalities. Finally, simulations are performed to show the effectiveness of the proposed method.
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