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Although the addition of excess sludge fermentation products to improve nutrient removal from sewage is cost‐effective, its application has rarely been demonstrated. In this study, the external sludge was first collected and fermented under a sludge retention time of 10 days, then introduced into SBR with a 1:15 sewage ratio. The results revealed a gradual increase in the nitrite accumulation ratio to 34.7% in the SBR at the end of the oxic stage after 64 days of adding fermented sludge products. In addition, the average effluent total nitrogen and phosphorous decreased to 7.3 and 0.5 mg/L, corresponding to removal efficiencies of 86.7% and 95.5%, respectively. On the other hand, the use of the fermented sludge products as external organic carbon sources in the SBR increased the external sludge reduction ratio to 42.5%. High‐throughput sequencing demonstrated that the increase in the endogenous denitrifier community, polyphosphate‐accumulating organisms, and fermentation bacteria were the main factors contributing to the increase in nutrient removal and excess sludge reduction. The economic evaluation indicated that the operational cost of the pilot‐scale system saves 0.011$/m3 of sewage treated. Practitioner Points: Fermented sludge addition effectively enhanced nutrient removal in pilot‐scale SBR.Average effluent TN and PO43−–P decreased to 7.3 and 0.5 mg/L, respectively.Highest external sludge reduction rate was 42.5% in pilot‐scale reactor.Sewage treatment cost can save 0.011$/m3 under advanced nutrient removal. [ABSTRACT FROM AUTHOR] more...

Alkaline fermentation of two distinct types of waste activated sludge was assessed to evaluate the recovery of by-products, such as nutrients, organic matter as a source of bioenergy, volatile fatty acids, and water. Also, to reduce the amount of solids to be disposed of, and the total management costs. Sludge 1 was from conventional activated sludge, and Sludge 2 was from a sequential batch reactor set for biological phosphorus removal. In the laboratory three different fermentation processes were provided in parallel, treating Sludge 1, followed by Sludge 2. Treatment A was the control, wherein the fermentation process occurred without alkali addition. Treatment B was alkaline fermentation with a controlled pH 10 of pre-solubilized sludge, and treatment C was alkaline fermentation at a controlled pH 10. The results indicated that alkaline fermentation significantly reduced the volatile suspended solids (VSS) to 45% treating Sludge 1, and to 50% treating Sludge 2, which was significantly improved for both sludges when pre-solubilized achieving 59% and 60%, respectively. Also, comparing the biogas production test of treatment A to the other conditions set, both increased almost four, and three times, for B and C, respectively. Orthophosphate, chemical oxygen demand, carbohydrates, and proteins in soluble fractions significantly increased under alkaline fermentation compared with the control, and all of these parameters were boosted with pre-solubilization. Comparing both sludges, the one from biological phosphorus removal systems achieved higher VSS reduction, and a significantly higher rate of orthophosphate release. [ABSTRACT FROM AUTHOR] more...

• Effects of different pH control treatments on WAS fermentation were studied. • The purity of VFAs were enhanced by initial pH 10 fermentation (RIA). • P removal efficiency and fermented sludge dewaterability was also improved in RIA. • VFAs via RIA was a better way to applied as carbon resource into the WWTP. Volatile fatty acids (VFAs) from waste activated sludge (WAS) via alkaline fermentation have been shown to provide an effective alternative carbon source for biological nutrient removal in wastewater treatment plants (WWTPs) that promotes the subsequent release of phosphorus (P) and refractory dissolved organic matter. The dewatering ability of fermented sludge is known to decrease during alkaline fermentation. Here, a novel strategy of initiating fermentation at a pH of 10 was developed to improve VFA purity, P removal efficiency, and fermented sludge dewaterability during WAS fermentation. Although VFAs concentration was lower (1.69 ± 0.09 g COD/L) when the pH was only initially adjusted to pH 10 (R IA) relative to when the pH was maintained at 10 on a daily basis (R DC), the purity of VFAs in the fermented liquid was improved (58.48%). Furthermore, the release of total phosphorous (TP) in R IA was 5.90 times lower than that in R DC (139.37 mg/L). The normalized capillary suction time and specific resistance to filtration in R IA decreased to 42.23% and 40.70%, respectively, suggesting that the dewaterability of fermented sludge also improved. The amount of alkali needed was 17.44 kg for each ton of total solid (TS) in R IA , which was 5.49 times lower than that in R DC. Thus, approximately 45.44 USD was saved in operational costs for each ton of TS processed in R IA. These results indicated that VFAs production via initial pH 10 fermentation was a robust and cost-efficient way for providing carbon resources in WWTPs. [ABSTRACT FROM AUTHOR] more...

In order to solve the problems of long sludge retention time and low efficiency in traditional sludge fermentation process, a new sludge pretreatment technology based on the mechanical stirring was proposed in this study. The effect of mechanical pretreatment on excess sludge fermentation was investigated. The results showed that mechanical pretreatment promoted the sludge flocs disinegration and cell lysis. When the mechanical stirring intensity was 21 000 r/min (pretreatment-1) and 35 000 r/min (pretreatment-2),the sludge particle size decreased from 66. 7 μm to 21. 9 μm and 16. 4 μm, and sludge disintegration degree was 10. 9% and 16. 9%, respectively. The sludge fermentation was improved by mechanical pretreatment, the yield of soluble chemical oxygen demand ( SCOD) and volatile fatty acids (VFAs) was significantly increased with the increasing of mechanical stirring intensity. The yield of SCOD and VFAs reached the maximum,when sludge retention time was 6 d. The maximum concentration of SCOD and VFAs were 5 102 and 3 469 mg/ Lin pretreatment-2 group, which were 96. 2% and 93% higher than those of the control group. The high-throughput sequencing analysis showed that microbial community composition was influenced by mechanical pretreatment. Firmicutes is the dominant bacteria in the fermentation system. The relative abundance of Firmicutes in the pretreatment-1 and pretreatment-2 was 88. 33 % and 96. 54 %, respectively, which was significantly higher than that of the control group (84. 38%),thus increased the yield of SCOD and VFAs. [ABSTRACT FROM AUTHOR] more...

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· S2EBPR was enabled in a pilot-scale mainstream shortcut n removal process. · 86% n removal and 87 % P removal were achieved in the final effluent. · A-stage WAS fermentation allowed carbon capture and redirection for effective EBPR. · High phylogenetic and phenotypic microdiversities observed within key PAOs. · PAO and GAO sub-groups and oligotypes correlated with p removal. While the adsorption/bio-oxidation (A/B) process has been widely studied for carbon capture and shortcut nitrogen (N) removal, its integration with enhanced biological phosphorus (P) removal (EBPR) has been considered challenging and thus unexplored. Here, full-scale pilot testing with an integrated system combining A-stage high-rate activated sludge with B-stage partial (de)nitrification/anammox and side-stream EBPR (HRAS-P(D)N/A-S2EBPR) was conducted treating real municipal wastewater. The results demonstrated that, despite the relatively low influent carbon load, the B-stage P(D)N-S2EBPR system could achieve effective P removal performance, with the carbon supplement and redirection of the A-stage sludge fermentate to the S2EBPR. The novel process configuration design enabled a system shift in carbon flux and distribution for efficient EBPR, and provided unique selective factors for ecological niche partitioning among different key functionally relevant microorganisms including polyphosphate accumulating organisms (PAOs) and glycogen-accumulating organisms (GAOs). The combined nitrite from B-stage to S2EBPR and aerobic-anoxic conditions in our HRAS-P(D)N/A-S2EBPR system promoted DPAOs for simultaneous internal carbon-driven denitrification via nitrite and P removal. 16S rRNA gene-based oligotyping analysis revealed high phylogenetic microdiversity within the Accumulibacter population and discovered coexistence of certain oligotypes of Accumulibacter and Competibacter correlated with efficient P removal. Single-cell Raman micro-spectroscopy-based phenotypic profiling showed high phenotypic microdiversity in the active PAO community and the involvement of unidentified PAOs and internal carbon-accumulating organisms that potentially played an important role in system performance. This is the first pilot study to demonstrate that the P(D)N-S2EBPR system could achieve shortcut N removal and influent carbon-independent EBPR simultaneously, and the results provided insights into the effects of incorporating S2EBPR into A/B process on metabolic activities, microbial ecology, and resulted system performance. [Display omitted] [ABSTRACT FROM AUTHOR] more...

Aluminum-based chemically enhanced primary sedimentation has seen increasing use in wastewater treatment plants. However, the derived sludge (Al-sludge) has low biodegradability due to the inhibition of Al-coagulants on organic hydrolysis, which increases the difficulty of sludge treatment and limits the potential for resource recovery. In this study, the effects of pH adjustment on the pretreatment and fermentation of Al-sludge was investigated, with a focus on sludge hydrolysis and production of volatile fatty acids (VFAs). The effects of abiotic and biotic hydrolysis on sludge disintegration, organics solubilization, and hydrolytic enzyme activity were also evaluated. The results show that adjustment of the pH to between 8.0 and 10.0 was more effective than adjustment to between 2.0 and 6.0 for sludge hydrolysis and subsequent VFA production. The enzymatic activities of protease and α -glucosidase showed a positive correlation with the pH values, leading to the highest VFA yield (275 mg-COD/g-VS) for the initial pH 10.0 condition, with 46% improvement over the control reactor (without pH adjustment). Semi-continuous fermentation was found to be more effective than batch fermentation for the biotic hydrolysis rate, k H . Little phosphorus (<0.1 mg/L) was released from the Al-sludge into the fermented sludge liquor, so P removal was not necessary before the VFAs were used. The wastewater treatment process with Al-based chemically enhanced primary sedimentation and pH adjustment for enhanced sludge fermentation can recover 24% of organic carbon from domestic wastewater. [ABSTRACT FROM AUTHOR] more...

An integrated membrane bioreactor (MBR) system was developed for enhanced nutrient (N and P) removal and effective P recovery in wastewater treatment. The system consisted of an iron-dosing MBR and side-stream fermentation for P removal and recovery and side-stream denitrification for N removal. Around 98.1% of the total phosphorus (TP) in wastewater was removed by ferric iron-induced precipitation and membrane filtration in the aerobic MBR, and nearly 53.4% of the TP could be recovered via anaerobic fermentation from the MBR sludge. In addition, the fermenter that allowed acidogenic co-fermentation with food waste provided sufficient soluble organics for biological denitrification, and an overall 91.8% total N removal was achieved through the side-stream denitrification. High-throughput sequencing was applied to analyse the microbial communities in the integrated system, and important functional bacteria were identified for nitrification, denitrification, acidogenic fermentation and dissimilatory iron reduction through the different components of the system. [ABSTRACT FROM AUTHOR] more...

Waste activated sludge (WAS) can become an important source of phosphorus (P). P speciation was examined under anaerobic conditions, with different pH (4, 6 and 8) and temperatures (10, 20 and 35 °C). Aqueous P was measured and an extraction protocol was used to find three solid phosphorus fractions. A pH of 4 and a temperature of 35 °C gave a maximum of 51% of total P solubilized in 22 days with 50% of total P solubilized in 7 days. Batch tests indicate that little pH depression is needed to release non-apatite inorganic P (including microbial polyphosphate), while a pH of 4 rather than 6 will release more apatite inorganic P, and that organic P is relatively more difficult to release from WAS. Fractionation analysis of P in WAS can aid in design of more efficient methods for P recovery from WAS. [ABSTRACT FROM AUTHOR] more...

[Display omitted] • Four different volatile fatty acids were used for sustainable biological nutrient removal. • High concentrations of acetic acid appear to benefit the proliferation of Defluviicoccus. • Valeric acid, commonly found in fermented sludge, appear to benefit nitrification. • The presence of VFAs with high molecular weight indicated to benefit denitrification. • DPAO capable of using nitrite as electron acceptor belonging to Clade IIC were existent. Different ratios of four volatile fatty acids (VFAs) were used as the primary feed to a laboratory scale biological nutrient reactor during four operational stages. The reactor performed efficiently over 500 days of operation with over 90% dissolved phosphorus and over 98% ammonium-nitrogen (NH 4 +-N) removal. Through in the first experimental phase, acetate and propionate were present in a significant proportion as carbon sources, the relative abundance of Candidatus Accumulibacter, a potential polyphosphate accumulating organism, increased from 10% to 57% and the Defluviicoccus genus, a known glycogen accumulating organism (GAO), decreased from 41% to 5%. Further tests indicated the presence of denitrifying phosphorus accumulating organisms (DPAO) belonging to Clade IIC, that could use nitrite as the electron acceptor during P-uptake. In general, VFAs favored the increase of the genus Defluviicoccus and Candidatus Accumulibacter. High relative abundance of Defluviicoccus did not affect the stability and the performance of the BNR process. [ABSTRACT FROM AUTHOR] more...

Iron-based chemically enhanced primary sedimentation (CEPS) is increasingly adopted for wastewater treatment in mega cities, producing a large amount of sludge (Fe-sludge) with a high content of organics for potential organic resource recovery. In this experimental study, acidogenic fermentation was applied treat FeCl 3 -based CEPS sludge for production of volatile fatty acids (VFAs) at different pHs. Batch fermentation tests on the Fe-sludge with an organic content of 10 g-COD/L showed that the maximum VFAs production reached 2782.2 mg-COD/L in the reactor without pH control, and it reached 688.4, 3095.3, and 2603.7 mg-COD/L in reactors with pHs kept at 5.0, 6.0 and 8.0, respectively. Analysis of the acidogenesis kinetics and enzymatic activity indicated that the alkaline pH could accelerate the rate of organic hydrolysis but inhibited the further organic conversion to VFAs. In semi-continuous sludge fermentation tests, the VFAs yield in the pH6 reactor was 20% higher than that in the control reactor without pH regulation, while the VFAs yield in the pH8 reactor was 10% lower than the control. Illumina MiSeq sequencing revealed that key functional microorganisms known for effective sludge fermentation, including Bacteroidia and Erysipelotrichi , were enriched in the pH6 reactor with an enhanced VFAs production, while Clostridia became more abundant in the pH8 reactor to stand the unfavorable pH condition. The research presented acidogenic fermentation as an effective process for CEPS sludge treatment and organic resource recovery and provided the first insight into the related microbial community dynamics. [ABSTRACT FROM AUTHOR] more...

Primary sludge from wastewater treatment is of rich organic contents that can be resource for recovery. However, the sludge derived from the chemically enhanced primary sedimentation (CEPS), especially using Al-based coagulants, features a rather low biodegradability and treatability due to the agglomeration of solid matters by the coagulant. In the present study, alkali pretreatments by three chemicals (NaHCO 3 , Na 2 CO 3 and NaOH) were applied to disintegrate Al-based CEPS sludge (Al-sludge) aggregates and improve its hydrolysis and biodegradability for fermentation and organic recovery. Results showed that alkali pretreatment significantly reduced the Al-sludge particle size and accelerated the release of the enmeshed organics. NaHCO 3 exhibited the best pretreatment result. At ambient temperature, the yield of volatile fatty acids (VFAs) of the Al-sludge pretreated by Na 2 CO 3 (initial pH 10) was improved by four times compared to the untreated sludge, resulting from both the improved abiotic and biotic hydrolysis effects. The effect of alkali pretreatment on Al-sludge was found to be mainly attributable to the pH adjustment rather than the alkalinity increase. Illumina MiSeq sequencing revealed that protein-fermenting bacteria Treponema and Bacteroides became dominant during fermentation of the alkali pretreated sludge. By PACl-based CEPS and enhanced sludge acidogenesis, around 17% of organics in municipal wastewater can be recovered, mainly in the form of VFAs, which is significantly greater than 6% by the conventional primary sedimentation and sludge fermentation. [ABSTRACT FROM AUTHOR] more...

FeCl 3 and PACl as coagulants in chemically enhanced primary sedimentation (CEPS) were compared in terms of their efficiencies in removing pollutants from wastewater and their effects on the acidogenic fermentation of CEPS sludge for resource recovery. PACl was found to be more effective than FeCl 3 for removing suspended solids by CEPS, with around 20% higher removal efficiency. However, the coagulated Al-sludge experienced more difficulty and had lower efficiency than Fe-sludge in organic hydrolysis and acidogenesis. The batch fermentation results showed that FeCl 3 dosed at 10–30 mg Fe/L sewage had little influence on sludge hydrolysis and volatile fatty acid (VFA) production, whereas an obvious inhibitory effect was observed for PACl in organic hydrolysis of the sludge. The specific hydrolysis rate constant ( K h,P ) for sludge fermentation decreased from 0.0321 for the sludge without PACl to 0.017 for the Al-sludge obtained at a dosage of 24 mg Al/L sewage . Compared to the Al-sludge, the Fe-sludge had a much higher VFA yield and significant PO 4 –P release during the sludge fermentation, which is attributed to the reduction of Fe(III) to Fe(II) under anaerobic conditions and the resulting disintegration of sludge flocs. By simple pH adjustment of the fermented Fe-sludge supernatant, up to 31% of the phosphorus in wastewater can be recovered in the form of vivianite as P fertilizers. VFAs produced in the supernatant are valuable organic carbon resources that can be recovered for beneficial uses. [ABSTRACT FROM AUTHOR] more...

In this work, a mathematical model was developed to describe the dynamics of fermentation products in sludge alkaline fermentation systems for the first time. In this model, the impacts of alkaline fermentation on sludge disintegration, hydrolysis, acidogenesis, acetogenesis, and methanogenesis processes are specifically considered for describing the high-level formation of fermentation products. The model proposed successfully reproduced the experimental data obtained from five independent sludge alkaline fermentation studies. The modeling results showed that alkaline fermentation largely facilitated the disintegration, acidogenesis, and acetogenesis processes and severely inhibited methanogenesis process. With the pH increase from 7.0 to 10.0, the disintegration, acidogenesis, and acetogenesis processes respectively increased by 53%, 1030%, and 30% while methane production decreased by 3800%. However, no substantial effect on hydrolysis process was found. The model also indicated that the pathway of acetoclastic methanogenesis was more severely inhibited by alkaline condition than that of hydrogentrophic methanogenesis. [ABSTRACT FROM AUTHOR] more...

A new chemically enhanced primary sedimentation (CEPS) and sludge fermentation process are developed for improved nutrient removal, energy saving and resource recovery in municipal wastewater treatment. The FeCl 3 -based CEPS with a dosage of 20 mg-Fe/L can remove 75.6% of organic pollutants and 99.3% of PO 4 -P on average from wastewater. Under natural fermentation conditions, the CEPS sludge undergoes effective hydrolysis and acidogenesis to produce volatile fatty acids (VFAs) and release phosphate as valuable resources. By using CEPS, around 27% of the organic carbon in wastewater influent can be recovered via sludge fermentation, mainly in the form of VFAs, and about 23% of phosphorus recovered for making vivianite fertilizer. In comparison, both the organic and phosphorus recovery ratios from wastewater are under 10% with conventional primary sedimentation and sludge fermentation. CEPS combined with side-stream sludge fermentation can be readily applied in new treatment plants or in a retrofit of existing treatment systems. [ABSTRACT FROM AUTHOR] more...

An integrated partial nitrification, sludge fermentation and denitrification process in a sequencing batch reactor (PNSFD-SBR), was developed to enhance nitrogen removal from domestic wastewater with low C/N (i.e. SCOD/TN) between 2 to 3 and to reutilize/reduce external waste activated sludge (WAS). Average ammonium removal efficiency of 95.9%, total nitrogen removal efficiency of 93.5%, and external WAS reduction rate of 21.6% was achieved during long-term experiment at 30 ± 1 °C. Real-time pH-DO (dissolved oxygen) monitor and control played an important role in the PNSFD achievement. A batch test indicated that micro-aeration (less than 1 mg/L) sustained partial nitrification, which further facilitated subsequent sludge fermentation and denitrification processes. Moreover, Illumina MiSeq analysis demonstrated the predominant bacteria were Rhodocyclaceae , Anaerolineaceae and Saprospiraceae on family level and they were key to partial nitrification, denitrification and sludge fermentation, by which the feasibility of PNSFD process to achieve simultaneous nitrogen removal and external WAS reutilization/reduction was verified. [ABSTRACT FROM AUTHOR] more...

Huge amounts of highly concentrated organic wastewater and sludge, which are main environmental pollutants that are highly difficult and costly to dispose of, are generated along with rapid industrialization and urbanization. Petroleum coke slurry (PCS) is an established liquid fuel that can be used as a substitute to oil and as a gasification material. However, the poor storage stability of PCS significantly constrains its applications. In this study, highly concentrated organic wastewater, sludge, and petroleum coke were mixed to prepare a new PCS with high storage stability. During sealed storage, biogas bubbles were produced and diffused in the prepared PCS because organic matter in wastewater was consumed by microorganisms in the sludge. Biogas bubbles bonded with petroleum coke particles and formed gas–solid combos. The lifting and steric hindrance effects of biogas effectively prevented petroleum coke particles from settling and coagulating, thus enhancing PCS storage stability and extending the application range of PCS. Based on the mathematical model and the stability results, the sludge significantly increased the spatial structure strength of PCS, and the fermentation biogas diffused in the slurry further increased structure strength and enhanced slurry stability. [ABSTRACT FROM AUTHOR] more...

Short-term fermentation of raw sludge from a high purity oxygen activated sludge systems was explored as a means of increasing the dissolved phosphorus and producing volatile fatty acids (VFA). Fermentation of primary sludge (PS), waste activated sludge (WAS), and co-thickened sludge (PS and WAS) showed significant phosphorus solubilization and VFA production at 2-4 days of fermentation in conditions of a completely mixed system of equal solids and liquid residence times. Factors found to have the most influence on phosphorus solubilization rates were sludge type, fermentation time, total phosphorus (TP) content in sludge, and process pH. WAS fermentation solubilized the most phosphorus per mass of volatile solids (VS) followed by co-thickened sludge. PS fermentation produced the most VFA per mass VS fermented while WAS produced the least. After 4 days of fermentation, co-fermented sludge converted 48 % of TP to dissolved phosphorus, and produced 1624 mg l of VFA-COD which corresponded to a VFA-COD yield per mass of 0.139 mg per mg VS applied. In terms of total sludge management, co-fermentation resulted in greater overall VFA production and phosphorus solubilization than individual sludge fermentation. [ABSTRACT FROM AUTHOR] more...

• A novel strategy to explore DOM transformation by FT-ICR MS and data mining. • DOM transformation patterns provide potential fingerprint tracking performance. • Keystone molecules in DOM network presented as potential indicator or regulators. Understanding the composition and reactivity of dissolved organic matter (DOM) at molecular level is vital for deciphering potential regulators or indicators relating to anaerobic process performance, though it was hardly achieved by traditional analyses. Here, the DOM composition, molecular reactivity and transformation in the enhanced sludge fermentation process were comprehensively elucidated using high-resolution mass spectrometry measurement, and data mining with machine learning and paired mass distance (PMD)-based reactomics. In the fermentation process for dewatered sludge, persulfate (PDS) pretreatment presented its highest performance in improving volatile fatty acids (VFAs) production with the increase from 2,711 mg/L to 3,869 mg/L, whereas its activation in the presence of Fe (as well as the hybrid of Fe and activated carbon) led to the decreased VFAs production performance. In addition to the conventional view of improved decomposition and solubilization of N-containing structures from sludge under the sole PDS pretreatment, the improved VFAs production was associated with the alternation of DOM molecular compositions such as humification generating molecules with high O/C, N/C, S/C and aromatic index (AI mod). Machine learning was capable of predicting the DOM reactivity classes with 74–76 % accuracy and found that these molecular parameters in addition to nominal oxidation state of carbon (NOSC) were among the most important variables determining the generation or disappearance of bio-resistant molecules in the PDS pretreatment. The constructed PMD-based network suggested that highly connected molecular network with long path length and high diameter was in favor of VFAs production. Especially, -NH related transformation was found to be active under the enhanced fermentation process. Moreover, network topology analysis revealed that CHONS compounds (e.g., C 13 H 27 O 8 N 1 S 1) can be the keystone molecules, suggesting that the presence of sulfur related molecules (e.g., cysteine-like compounds) should be paid more attention as potential regulators or indicators for controlling sludge fermentation performance. This study also proposed the non-targeted DOM molecular analysis and downstream data mining for extending our understanding of DOM transformation at molecular level. [Display omitted] [ABSTRACT FROM AUTHOR] more...

Anaerobic fermentation of the enhanced biological phosphorus removal (EBPR) sludge was investigated in terms of phosphate release and volatile fatty acids (VFAs) production regarding polyphosphate accumulating organisms (PAOs) activity. PAOs decay rate during fermentation was determined as 0.35 ± 0.03 d −1 . Sludge lysis was enhanced with an increase in polyhydroxyalkanoate (PHA) content. Moreover, the phosphate release profiles and the VFAs production as well as the individual VFA fractions varied with different acetate concentrations added initially. Based on these observations, anaerobic digestion model No. 1 was extended and modified by introducing: (1) processes that PAOs store 4 VFA species as PHA, which can be degraded into varied fractions of individual VFA in dependence on PHA composition, (2) the effect of PHA content on disintegration rate, and (3) phosphorus precipitation. The proposed model adequately fitted a multi-experiment, multi-variable data set, indicating that it plays an important role in predicting phosphate and VFAs variations during EBPR sludge fermentation. [ABSTRACT FROM AUTHOR] more...

Long-term effect of pH (4, 10, and uncontrolled) on short-chain fatty acid (SCFA) accumulation, microbial community and sludge reduction were investigated in waste activated sludge (WAS) fermentors for over 90 days. The average SCFAs accumulation was 1721.4 (at pH 10), 114.2 (at pH 4), and 58.1 (at uncontrolled pH) mg chemical oxygen demand (COD)/L. About 31.65 mg COD/L was produced at pH 10, accounting for 20% of the influent COD. Illumina MiSeq sequencing revealed that Alcaligenes (hydrolic bacteria) and Erysipelothrix (acidogenic bacteria) were enriched at pH 10, while less acidogenic bacteria existed at pH 4 than pH 10, and no acidogenic bacteria were detected at the uncontrolled pH. The ratios of archaea to bacteria were 1:41, 1:16, and 1:9 at the pH of 10, 4, and uncontrolled. This study elucidated the effects of pH on WAS fermentation, and established the correlation of microbial structure with SCFAs accumulations and sludge reduction. [ABSTRACT FROM AUTHOR] more...

The ultrasonic disintegration of excess sludge is placed after the mechanical thickening but before the digestion tanks in order to intensify the process of sludge stabilization. The effects obtained directly after ultrasonic disintegration depend on many factors and can be grouped in two main categories: factors affecting the quality of sludge and those associated with the construction of disintegrators and its parameters. The ultrasonic disintegration research was carried out using three types of structural solutions of disintegrators. Two of them, that is, WK-2000 ultrasonic generator (P = 400 W) working with a thin sonotrode and WK-2010 ultrasonic generator (P = 100–1000 W) working with a new type construction emitter lens sonotrode, were compared with the influence of a washer with a flat emitter. The investigations have shown that in the same sludge, using the same value of volumetric energy, the resulting effect depends on the construction of the ultrasonic disintegrator, that is, design of the head and the ratio between the field of the emitter and the field of the chamber in sonicated medium. [ABSTRACT FROM PUBLISHER] more...

Sludge fermentation between pH 4 and 11 was investigated to generate volatile fatty acids (VFA). Despite the highest sludge solubilization of 25.9% at pH 11, VFA accumulation was optimized at pH 8 (12.5% out of 13.1% sludge solubilization). 454 pyrosequencing identified wide diversity of acidogens in bioreactors operated at the various pHs, with Tissierella , Petrimonas , Proteiniphilum , Levilinea , Proteiniborus and Sedimentibacter enriched and contributing to the enhanced fermentation at pH 8. Hydrolytic enzymatic assays determined abiotic effect to be the leading cause for improved solubilization under high alkaline condition but the environmental stress at pH 9 and above might lead to disrupt biological activities and eventually VFA production. Furthermore, molecular weight (MW) characterization of the soluble fractions found large MW aromatic substances at pH 9 and above, that is normally associated with poor biodegradability, making them disadvantageous for subsequent bioprocesses. The findings provided information to better understand and control sludge fermentation. [ABSTRACT FROM AUTHOR] more...

A pilot-scale process was operated over 22 months at the Brussels North Wastewater Treatment Plant (WWTP) in order to evaluate polyhydroxyalkanoate (PHA) production integration with services of municipal wastewater and sludge management. Activated sludge was produced with PHA accumulation potential (PAP) by applying feast–famine selection while treating the readily biodegradable COD from influent wastewater (average removals of 70% COD, 60% COD sol , 24% nitrogen, and 46% phosphorus). The biomass PAP was evaluated to be in excess of 0.4 gPHA/gVSS. Batch fermentation of full-scale WWTP sludge at selected temperatures (35, 42 and 55 °C) produced centrate (6–9.4 gCOD VFA /L) of consistent VFA composition, with optimal fermentation performance at 42 °C. Centrate was used to accumulate PHA up to 0.39 gPHA/gVSS. The centrate nutrients are a challenge to the accumulation process but producing a biomass with 0.5 gPHA/gVSS is considered to be realistically achievable within the typically available carbon flows at municipal waste management facilities. [ABSTRACT FROM AUTHOR] more...

Abstract: The production of volatile fatty acids (VFAs) from primary sludge and the subsequent application to improve biological nutrient removal has drawn much attention. In this study, a novel approach of using primary sludge as an additional carbon source was conducted in batch tests. The nitritation effluent was directly injected into the sludge fermentation reactor to achieve nitrogen removal. Complete denitrification could be realized in the combined reactor. Moreover, injecting nitrite not only promoted the sludge stabilization process, but also reduced the release of phosphate and ammonium during sludge stabilization. The novel process was further evaluated in a continuous system by treating sludge dewatering liquors. Under optimum conditions, 85% removal of ammonium and 75% of total nitrogen could be obtained using primary sludge, resulting in the suitable effluent for recycling into the inlet of the wastewater treatment plant. [Copyright &y& Elsevier] more...

Abstract: In this study, a novel denitrification reactor is used to treat sludge dewatering liquor, where the co-occurrence of sludge fermentation and nitrate reduction was obtained. The system showed an efficient and stable nitrogen removal performance. When the effluent recycle ratio was 200%, TN and removal efficiency was 99.6% and 83.5%, respectively. In addition, primary sludge could be well degraded in the novel system. Over 50% volatile suspended solid (VSS) of primary sludge was utilized, and the ratio of VSS/SS declined from 0.76 to 0.39. Further investigation with batch experiments revealed that, compared to conventional sludge fermentation, the integration of denitrification and fermentation was better at carbon production as well as the control of ammonium release. [Copyright &y& Elsevier] more...

Pretreatment technologies for improving the anaerobic digestion of waste activated sludge have been studied extensively; however, studies on the improvement of pretreatment technology for primary sludge (PS) fermentation and anaerobic digestion are scarce. In this study, a novel mechanical cutting pretreatment (MCP) method was proposed to enhance the performance of PS fermentation and anaerobic digestion. PS was disintegrated by MCP, the average particle size of PS reduced from 45.7 µm to 7.0 µm, and soluble COD (SCOD) increased by 1206 mg/L with pretreatment for 8 min. The hydrolysis and acidification of PS was promoted significantly by MCP. Compared with the control group, the production of SCOD and volatile fatty acids (VFAs) in the pretreatment group during sludge fermentation increased by 167% and 115.3%, respectively. The performance of PS anaerobic digestion was remarkably improved by MCP. The maximum cumulative biogas production in the pretreatment group was 3153 mL, which was 6.33 times that in the control group (498.5 mL). Sludge disintegration by mechanical pretreatment resulted in the enrichment of bacteria, especially Firmicutes , in the sludge fermentation system, and the quantity of bacteria in the pretreatment group was 1.95 times that in the control group. However, MCP had little effect on archaea in the anaerobic digestion of PS, and the methanogens in the control and pretreatment reactors were 1.493 × 109 and 1.519 × 109 copies/g, respectively. [Display omitted] • Primary sludge was crushed by mechanical cutting and particle size reduced by 84.7%. • VFAs yield in sludge fermentation increased by 115.3% after mechanical pretreatment. • Biogas yield in anaerobic digestion increased by 5.33 times by cutting pretreatment. • Primary sludge disintegration resulted in Firmicutes enrichment. [ABSTRACT FROM AUTHOR] more...

Abstract: New wastewater treatment processes resulting in considerably reduced sludge production and more effective treatment are needed. This is due to the more stringent legislations controlling discharges of wastewater treatment plants (WWTPs) and existing problems such as high sludge production. In this study, the feasibility of implementing biological hydrolysis and acidification process on different types of municipal sludge was investigated by batch and semi-continuous experiments. The municipal sludge originated from six major treatment plants located in Denmark were used. The results showed that fermentation of primary sludge produced the highest amount of volatile fatty acids (VFAs) and generated significantly higher COD- and VFA-yields compared to the other sludge types regardless of which WWTP the sludge originated from. Fermentation of activated and primary sludge resulted in 1.9–5.6% and 8.1–12.6% COD-yields, soluble COD (SCOD)/total COD (TCOD), in batch experiments, respectively. The COD-yields for primary, activated and mixed sludge were 19.1%, 6.5% and 21.37%, respectively, in semi-continuous experiments operated at solids retention time (SRT) of 5d and temperature of 37°C. The benefit of fermentation for full-scale application was roughly estimated based on the experiments performed in semi-continuous reactors. The results revealed that even though the VFA production of primary sludge was higher compared to activated sludge, substantial amounts of VFA could be produced by fermentation of activated sludge due to the substantially higher production of activated sludge in WWTPs. [Copyright &y& Elsevier] more...

• Sludge alkaline fermentation enhanced partial nitrification and anammox. • The abundance of NOB was reduced by 8.4 times. • The abundance of anammox bacteria has increased by 80.5 times. • NAR reached 60.40% and the contribution rate of anammox was as high as 47.17%. • No external carbon source dosing and short HRT oxic (5.3 h) could save energy. A continuous-flow anaerobic/aerobic/anoxic reactor with complete suspended activated sludge using sludge alkaline fermentation products as carbon source was utilized to strengthen nitrogen removal performance for low C/N ratio (<4) wastewater. Long-time performance indicated that the nitrite accumulation rate reached 60.40%, which strengthened the contribution of anammox. The average total inorganic nitrogen removal efficiency improved 19.40%. The abundance of ammonia oxidizing bacteria has not changed, but the abundance of nitrite oxidizing bacteria reduced from 5.79% to 0.69%. Quantitative PCR results demonstrated that the abundance of anammox bacteria has raised by 80.5 times. These results indicated that side-stream sludge alkaline fermentation promoted the mainstream partial nitrification, consequently accelerating the in-situ enrichment of anammox bacteria. No external carbon source dosing and short oxic hydraulic retention time (5.3 h) save energy and reduce consumption significantly in this system. [ABSTRACT FROM AUTHOR] more...

• IEAP pretreatment enhanced total SCFAs production in sludge fermentation. • IEAP pretreatment promoted acetate yield remarkably. • IEAP pretreatment decreased the acetate consumption but have inverse impact on propionic acid and sulfate. • IEAP pretreatment altered community structure and stimulated the growth of SRB. Iron activating persulfate has been recently used to pretreat waste activated sludge (WAS) to enhance short chain fatty (SCFAs) production, especially acetate production. However, details of how iron activating persulfate enhances acetate production remain largely unknown and direct use of scrap iron or powder iron causes either iron precipitation or loss, which would limit its practical application. This work therefore aims to provide such supports in an iron electrode activated persulfate (IEAP) system. In the study, before anaerobic fermentation, WAS was pretreated in IEAP reactors which employed sheet iron as anode and contained persulfate. Experimental results showed that when WAS was pretreated by IEAP (100 mA and 50 mg S 2 O 8 2 - /g TSS addition) for 60 min, 249.80 mg COD/g VSS of total SCFAs and 171.41 mg COD/g VSS of acetate (~86.13% of the total SCFAs) were respectively obtained at 3d and 7d, which was 136.4% and 167.2% of those obtained in the control. Further investigation found that in IEAP system, PS, SO 4 - · and S 2 O 8 2 - promote cell lysis and offered propionic ecology, most of propionic acid was transformed to acetate under the action of sulfate-reducing bacteria (SRB), which can be stimulated by current, sheet iron and SO 4 2 -. Illumina Miseq sequencing analysis confirmed that the relative abundance of SRB in the IEAP reactor was higher than that in control. Economic analysis indicated that sludge anaerobic fermentation with IEAP pretreatment is a cost-effective approach for WAS to energy sources. The finding obtained in this work provided insights into acetate produce process with IEAP-pretreatment sludge fermentation and might have important implications for further manipulation of WAS treatment and individual SCFAs regulation in the future. [ABSTRACT FROM AUTHOR] more...

Cement kiln collaborative disposal of municipal solid waste incineration (MSWI) fly ash (referred to as fly ash) can achieve harmless recycling of fly ash. However, because of high chlorine (Cl) content in fly ash, the practical application of this technology is seriously restricted. In order to find a suitable leaching solvent for dechlorination of fly ash, this study compared the effect of lactic acid fermentation liquid (FL) and sludge FL of food waste on dechlorination. Results show that 90% of water-insoluble Cl in fly ash can be removed by a three-step leaching process with lactic acid FL and sludge FL, and the Cl content in leached fly ash residue is 0.44% and 0.39%, respectively. According to calculation, permissible fraction of the residue after three-step leaching with addition of lactic acid FL and sludge FL in kiln is 4.28% and 4.99% higher than that of the residue after three-step leaching with pure water, respectively. Furthermore, the properties of leaching solvents after leaching experiments indicate that organic acids with low pH value and high concentration are more conducive for removal of water-insoluble Cl. Therefore, it is feasible to use two kinds of FL as leaching solvent for fly ash dechlorination. [ABSTRACT FROM AUTHOR] more...