Upgrading VFAs bioproduction from waste activated sludge via co-fermentation with soy sauce residue

Conditioning of extra carbon sources has been widely reported to facilitate fermentation of waste activated sludge (WAS). Soy sauce residue (SSR) was a relatively untapped carbon source for sludge conditioning. This batch study aimed to evaluate the possible implementation of SSR for volatile fatty acids (VFAs) production from WAS. To upgrade the bioavailability of feedstock, three typical pretreatment methods were conducted, i.e., ammonium hydroxide (AH), sulfuric acids (SA) and thermal assisted alkaline (TA). AH pretreated test (AH-PT) outperformed due to a relatively strong structure decomposition of cellulosic materials as revealed by infrared spectroscopic analysis and crystal index. As a result, performed a high hydrolysis rate of 4449 mg COD/d, 1.12-1.23-fold higher than that in TA and SA pretreated tests (TA-PT and SA-PT), and 7.8-fold higher than that in the Control test. Meanwhile, a volatile fatty acids (VFAs) contribution of 401.2 mg COD/g SSR L and a maximum acidification rate of 3.59 d was recorded, with a high sum proportion of mall molecular acetic and propionic 82.2%, 11%-70% increase over the other three tests. Besides, speciation process characterized with functional genus differentiation was identified by microbial diversity and distribution investigation and canonical correspondence analysis (CCA). Finally, a potential market value of 0.49-0.65 Billion €/year was preliminary estimated, showing promise of resource recovery from both WAS and SSR instead of extensive disposal.

Acceleration of the particulate organic matter hydrolysis by start-up stage recovery and its original microbial mechanism

To address the availability of carbon sources for denitrification,the accelerated hydrolysis of the most abundant but low-availability fraction of particulate organic matter(POM)was investigated.Mesh sieves with different pore sizes were used as primary pretreatment at the start-up-stage of the biological process to separate some POM from the liquid system.The changes in soluble carbohydrates and proteins were monitored to investigate the hydrolysis performance of the sieved POM,with waste activated sludge(WAS)as the control test.The results showed that an average of 35%POM could be entrapped before filtrate mat development.In addition,benefiting from the high polysaccharides concentration,as well as the high availability due to the relatively loose physical structure,a 23%hydrolysis efficiency of POM was obtained,in contrast to that of WAS(3.4%),with a hydrolysis constant of 0.39 h^(−1).The prominent performance was also attributed to the unique microbial communities having been domesticated at a lower temperature,especially the cellulose-degrading bacteria Paraclostridium and psychrophile Psychrobacter,making up 6.94%and 2.56%,respectively.Furthermore,the potential benefits and application of improved POM hydrolysis by start-up stage recovery via mesh sieves combined with anaerobic fermentation were evaluated,including selective POM entrapment,alleviation of blockage and wear,and a reduction in aeration energy.By the proposed strategy,carbon availability for biological nutrient removal(BNR)processes is anticipated to be improved more economically than that can be achieved by primary clarifier elimination.