Enhancing sludge biodegradability and volatile fatty acid production by tetrakis hydroxymethyl phosphonium sulfate pretreatment.

A new pretreatment method based on tetrakis hydroxymethyl phosphonium sulfate (THPS) biocide was tried to enhance sludge disintegration, and improved sludge biodegradability and subsequent volatile fatty acid (VFA) production. Sludge activity decreased to less than 10% after 2 days pretreatment using 20mg/g-TSS THPS, which also obviously destroyed EPS and cell membrane, and dissolved more biodegradable substances (48.8%) than raw sludge (19.7%). Moreover, 20mg/g-TSS THPS pretreatment shortened fermentation time to 4days and improved VFA production to 2778mg COD/L (4.35 times than that in control). Therein, the sum of n-butyric, n-valeric and iso-valeric acids unexpectedly accounted for 60.5% of total VFA (only 20.1% of that in control). The more high molecular weight VFAs (C4-C5) than low molecular VFAs (C2-C3) resulted from THPS pretreatment benefited to subsequent medium-chain volatile acids (C6-C12) generation to realize the separation and recovery of organic carbon more efficiently.

Enhanced volatile fatty acid production from excess sludge by combined free nitrous acid and rhamnolipid treatment.

VFA production from excess sludge (ES) was greatly enhanced by a low-cost and high-efficient treatment: 0.67mg/L free nitrous acid (FNA) pretreatment combined with 0.04g/g TSS rhamnolipid (RL) addition (FNA+RL), which significantly shortened fermentation time to 3days and increased VFA production to 352.26mgCOD/g VSS (5.42 times higher than raw ES). Propionic and acetic acids were the two leading components (71.86% of the total VFA). Mechanism investigation manifested FNA+RL improved the biodegradability of ES, achieved positive synergetic effect on solubilization, hydrolysis and acidification efficiencies, and inhibited methanation. Microbial community distribution further explained the above phenomena. The bacteria related to polysaccharides/protein utilization and VFA generation, including Clostridium, Megasphaera and Proteiniborus, were mainly observed in FNA+RL, whereas gas-forming bacteria Anaerolineae and acid-consuming bacteria Proteobacteria were assuredly suppressed. Besides, Propionibacterineae associated with propionic acid generation was exclusively enriched in sole RL and FNA+RL.

Removal of cephalosporin antibiotics 7-ACA from wastewater during the cultivation of lipid-accumulating microalgae.

The aim of this study is to evaluate the feasibility of using lipid-accumulating microalgae to remove cephalosporin antibiotics 7-amino cephalosporanic acid (7-ACA) from wastewater with the additional benefit of biofuels production. Three isolated microalgal strains (namely, Chlorella sp. Cha-01, Chlamydomonas sp. Tai-03 and Mychonastes sp. YL-02) were cultivated under 7-ACA stress and their biomass productivity, lipid production and N-NO3- consumption were monitored. It was found that 7-ACA had slight inhibition effects on the microalgal growth at the ratio of 12.0% (Cha-01), 9.6% (YL-02), 11.7% (Tai-03). However, lipid accumulation in the three microalgae was not influenced by the presence of 7-ACA. The investigation on the 7-ACA removal mechanisms during microalgal growth shows that 7-ACA was mainly removed by microalgae adsorption as well as hydrolysis and photolysis reactions. This study demonstrates that using microalgae to treat antibiotic-containing wastewater is promising due to the potential of simultaneous antibiotic removal and biofuel production.

Enhancement of volatile fatty acid production by co-fermentation of food waste and excess sludge without pH control: The mechanism and microbial community analyses.

The study provided a cost-effective and high-efficiency volatile fatty acid (VFA) production strategy by co-fermentation of food waste (FW) and excess sludge (ES) without artificial pH control. VFA production of 867.42mg COD/g-VS was obtained under the optimized condition: FW/ES 5, solid retention time 7d, organic loading rate 9g VS/L-d and temperature 40°C. Mechanism exploration revealed that the holistic biodegradability of substrate was greatly enhanced, and proper pH range (5.2-6.4) was formed by the high buffering capacity of the co-fermentation system itself, which effectively enhanced hydrolysis yield (63.04%) and acidification yield (83.46%) and inhibited methanogenesis. Moreover, microbial community analysis manifested that co-fermentation raised the relative abundances of hydrolytic and acidogenic bacteria including Clostridium, Sporanaerobacter, Tissierella and Bacillus, but suppressed the methanogen Anaerolineae, which also facilitated high VFA production. These results were of great guiding significance aiming for VFA recovery from FW and ES in large-scale.

Sulfamethoxazole degradation by ultrasound/ozone oxidation process in water: kinetics, mechanisms, and pathways.

In this research, sulfamethoxazole (SMX) degradation was investigated using ultrasound (US), ozone (O3) and ultrasound/ozone oxidation process (UOOP). It was proved that ultrasound significantly enhanced SMX ozonation by assisting ozone in producing more hydroxyl radicals in UOOP. Ultrasound also made the rate constants improve by kinetics analysis. When ultrasound was added to the ozonation process, the reaction rate increased by 6-26% under different pH conditions. Moreover, main intermediates oxidized by US, O3 and UOOP system were identified. Although the main intermediates in ozonation and UOOP were similar, the introduction of ultrasound in UOOP had well improved the cleavage of S-N bond. In this condition SMX become much easier to be attacked, which led to enhanced SMX removal rate in UOOP compared to the other two examined processes. Finally, the SMX degradation pathways were proposed.