Integrating waste activated sludge (WAS) acidification with denitrification by adding nitrite (NO2−)

Wang, Bo; Wang, Shuying; Li, Baikun; Cui, Peng; Peng, Yongzhen

doi:10.1016/j.biombioe.2014.05.015

Cited by 33 publications

(15 citation statements)

References 34 publications

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“…Apart from FNA, it was obvious that nitrite and pH in these integrated reactors were also different from those in the sole pH 10 reactor. It was reported that nitrite can be removed via denitrification in both acidic and alkaline fermentation systems (Wang et al, 2014a), and nitrite reduction was also observed in all nitrite added reactors in this study (Table S1, Supporting Information). Thus, it is necessary to confirm whether nitrite and pH 6 in the pretreatment step make contributions to the increased SCFA production.…”

Section: 2mentioning

confidence: 55%

“…To date, however, the effect of FNA pretreatment on SCFA production from sludge anaerobic alkaline fermentation has seldom been reported. Although some scientists pointed out that WAS with FNA treatment could increase sludge particulate release (Wang et al, 2014a), the underlying mechanisms are still needed to be elucidated. Moreover, whether FNA pretreatment integration with alkaline fermentation causes positive synergies on SCFA production also remains unknown.…”

Section: Introductionmentioning

confidence: 99%

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Free nitrous acid serving as a pretreatment method for alkaline fermentation to enhance short-chain fatty acid production from waste activated sludge

et al. 2015

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Alkaline condition (especially pH 10) has been demonstrated to be a promising method for short-chain fatty acid (SCFA) production from waste activated sludge anaerobic fermentation, because it can effectively inhibit the activities of methanogens. However, due to the limit of sludge solubilization rate, long fermentation time is required but SCFA yield is still limited. This paper reports a new pretreatment method for alkaline fermentation, i.e., using free nitrous acid (FNA) to pretreat sludge for 2 d, by which the fermentation time is remarkably shortened and meanwhile the SCFA production is significantly enhanced. Experimental results showed the highest SCFA production of 370.1 mg COD/g VSS (volatile suspended solids) was achieved at 1.54 mg FNA/L pretreatment integration with 2 d of pH 10 fermentation, which was 4.7- and 1.5-fold of that in the blank (uncontrolled) and sole pH 10 systems, respectively. The total time of this integration system was only 4 d, whereas the corresponding time was 15 d in the blank and 8 d in the sole pH 10 systems. The mechanism study showed that compared with pH 10, FNA pretreatment accelerated disruption of both extracellular polymeric substances and cell envelope. After FNA pretreatment, pH 10 treatment (1 d) caused 38.0% higher substrate solubilization than the sole FNA, which indicated that FNA integration with pH 10 could cause positive synergy on sludge solubilization. It was also observed that this integration method benefited hydrolysis and acidification processes. Therefore, more SCFA was produced, but less fermentation time was required in the integrated system.

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Section: 2mentioning

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Free nitrous acid serving as a pretreatment method for alkaline fermentation to enhance short-chain fatty acid production from waste activated sludge

et al. 2015

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“…It is worthwhile to note that compared with T‐VFAs in the blank test (with neither SDS nor nitrite addition), they were much higher at SDS dosage of 0 g/g (with initial nitrite concentration of 100 mg N/L) during the experiment, indicating that denitritation reaction enhanced sludge acidification as previous studies reported . Further comparison between T‐VFAs at SDS dosages of 0.02–0.1 g/g blank test samples (SDS = 0) showed that T‐VFAs improved by 1.8 times compared to blank test after 4 h. However, it kept almost the same at SDS dosages of 0.15–0.2 g/g (Fig.…”

Section: Resultsmentioning

confidence: 58%

“…A novel‐integrated WAS fermentation and denitritation (WASFD) process was put forward in which denitritation occurred by using organic compounds produced from in situ sludge fermentation . Due to the feeding or generating of NO 2 − , oxidation‐reduction potential (ORP) is thus increased in this process .…”

Section: Introductionmentioning

confidence: 99%

Enhancement of Integrated Waste Activated Sludge Fermentation and Denitritation by Addition of Sodium Dodecyl Sulfate

Wang

et al. 2016

CLEAN Soil Air Water

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Integrated waste activated sludge fermentation and denitritation (WASFD) is an efficient energy-saving approach to treat wastewater and sludge at the same time. This study aimed at simultaneously promoting WASFD by adding sodium dodecyl sulfate (SDS). The batch-mode tests showed that total volatile fatty acids (consisting of VFAs consumed for denitritation and VFAs observed) increased significantly at SDS dosages of 0.02-0.1 g/g dry sludge at room temperature. After 12 h, the released ammonium nitrogen reached the peak value at 0.1 g/g SDS, and decreased by 75.1% at 0.02 g/g SDS. Released phosphorus decreased by 63.1% at 0.02 g/g SDS compared to the peak value at 0.15 g/g SDS. Further investigation showed that the denitritation rate was enhanced at 0.02-0.05 g/g SDS. From the above, a suitable SDS dosage of 0.02 g/g is beneficial for WASFD with a relatively minor undesirable nutrient release from sludge fermentation.

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“…It suggested that nitrite addition caused more colloidal organic matter in sludge floc transfer into dissolved organic matter (DOM). Proteins and polysaccharides had been proven to be the main constituents of WAS, and the process of WAS hydrolysis could be expressed by the change of soluble proteins and polysaccharides concentrations (Wang et al 2014a;Luo et al 2014). As shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Hydrolysis and volatile fatty acids accumulation of waste activated sludge enhanced by the combined use of nitrite and alkaline pH

Huang

Liu

Sun

et al. 2015

Environ Sci Pollut Res

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Volatile fatty acids (VFAs) production from anaerobic digestion of waste activated sludge (WAS) is often limited by the slow hydrolysis and/or poor substrate availability. Increased attention has been given to enhance the hydrolysis and acidification of WAS recently. This study presented an efficient and green strategy based on the combined use of nitrite pretreatment and alkaline pH to stimulate hydrolysis and VFA accumulation from WAS. Results showed that both proteins and polysaccharides increased in the presence of nitrite, indicating the enhancement of sludge solubilization and hydrolysis processes. Mechanism investigations showed that nitrite pretreatment could disintegrate the sludge particle and disperse extracellular polymeric substances (EPS). Then, anaerobic digestion tests demonstrated VFA production increased with nitrite treatment. The maximal VFA accumulation was achieved with 0.1 g N/L nitrite dosage and pH 10.0 at a sludge retention time (SRT) of 7 days, which was much higher VFA production in comparison with the blank, sole nitrite pretreatment, or sole pH 10. The potential analysis suggested that the combined nitrite pretreatment and alkaline pH is capable of enhancing WAS digestion with a great benefit for biological nutrient removal (BNR).

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Integrating waste activated sludge (WAS) acidification with denitrification by adding nitrite (NO2−)

Cited by 33 publications

References 34 publications

Free nitrous acid serving as a pretreatment method for alkaline fermentation to enhance short-chain fatty acid production from waste activated sludge

Free nitrous acid serving as a pretreatment method for alkaline fermentation to enhance short-chain fatty acid production from waste activated sludge

Enhancement of Integrated Waste Activated Sludge Fermentation and Denitritation by Addition of Sodium Dodecyl Sulfate

Hydrolysis and volatile fatty acids accumulation of waste activated sludge enhanced by the combined use of nitrite and alkaline pH

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