Feasibility of short-term fermentation for short-chain fatty acids production from waste activated sludge at initial pH10: Role and significance of rhamnolipid

Abstract

Short-term fermentation for SCFAs production from WAS had been proposed. RL pretreatment enhanced WAS hydrolysis/acidification under alkaline conditions. Role and significance of EPSs had been investigated. The cumulative SCFAs were better fitted with pseudo-first-order kinetic model. RL + initial pH 10 caused positive synergies on anaerobic fermentation process. a r t i c l e i n f o b s t r a c tShort-chain fatty acids (SCFAs), preferred carbon source for enhanced biological nutrients removal system, can be produced from anaerobic fermentation of waste activated sludge (WAS). Hydrolysis is known as the rate-limiting step for SCFAs production. This study presents a novel technology using rhamnolipid (RL) pretreatment connected alkaline anaerobic fermentation to enhance SCFAs production. Experiment results showed that the integration treatments performed significant enhancement of SCFAs production, and the fermentation time was remarkably shortened. The maximum SCFAs production, 378 mg COD/g VSS (volatile suspended solid), reached at 72-h fermentation time under 0.2 g RL/g TSS (total suspended solid) and initial pH 10 treatment, which was 4.31, 1.32 and 1.24 times higher than that of control, initial pH 10 and 0.2 g RL/g TSS treatment, respectively. The mechanism study showed that integration treatments could enhance the release of constituents from the cells and/or extracellular polymeric substances to suspension, and hydrolysis rate constant was improved greatly in integration treatment, 8.68, 2.14 and 1.55 times higher than that of control, sole RL and initial pH 10 treatments, respectively. The results suggested that positive synergy led to improvement of WAS solubilization and SCFAs production under integration conditions. The pseudo-first-order model was successfully built to present the SCFAs accumulation. Therefore, the integration method in this work was a promising technology for SCFAs production enhancement from WAS.

Clarification of phosphorus fractions and phosphorus release enhancement mechanism related to pH during waste activated sludge treatment

“…Based on the findings obtained in this work and referenced the previous study (He et al, 2016a), a new door may be opened for WAS and WW treatments. As shown in Fig.6, an alternative and potential outline for both resource recovery from WAS and CS supplementation for WW treatment in situ in WWTPs is proposed.…”

“…S5 (B)). As well known, the available biodegradable COD in influent, cannot meet the carbon source (CS) demand for nutrients removal in biological WW treatment process, especially EBPR process (He et al, 2016a). Considering that chemically synthesized CS (e.g., acetate, propionate and glucose) is neither cost-effective nor sustainable (He et al, 2016a), it is of great significance if the SCFAs produced during P release process can be recovered as the external CS in situ in full scale WWTPs.…”

Pre-treatments to enhance the biodegradability of waste activated sludge: Elucidating the rate limiting step

“…The latter method fosters the endogenous enzyme (or enzyme-producing microorganisms) (S. Yu et al, 2013). Recently, surfactants that can be biologically produced by many different microorganisms, such as rhamnolipids, have been used for pre-treatment (He et al, 2016;Kavitha et al, 2016, Kavitha et al, 2014Zhou et al, 2013). According to Zhou et al (2013), rhamnolipids increase the solubility of compounds and provoke the EPS to detach from the attached cell surface.…”

Volatile Fatty Acids Production from Codigestion of Food Waste and Sewage Sludge Based onβ-Cyclodextrins and Alkaline Treatments

“…It was obvious that good agreement was achieved between calculated and experimental results, with strong correlation coefficients ( R 2 : 0.962–0.999), low ARE (%) (0.024–0.900 < 1), and Δ q  (%) (1.553–9.490 < 10) (Table 2), suggesting that the hydrolysis of protein/polysaccharides from the mixture (FW and SS) obeyed the PFO model. In terms of sludge, both PFO and first-order models have been successfully used to fit the hydrolysis of polymeric substances [15, 28]. The highest hydrolysis rate constants of protein and polysaccharides were obtained in combined tests, 2.13 (protein) and 3.45 (polysaccharides) times higher than control test.…”