[Characteristics of Partial Denitrification in Biofilm System].

As an intermediate form of microbial denitrification, nitrite serves as a key substrate for anaerobic ammonium oxidation (ANAMMOX). This study investigated the partial dentification (PD) characteristics and the coupling feasibility of PD+ANAMMOX in the biofilm system, using a moving bed biofilm reactor which was operated for 120 days. After 40 days of operation with a C/N ratio of 3.0 and filling fraction of 20%, the nitrate-to-nitrite transformation ratio (NTR) reached (69.38±3.53)%, and enzymatic assays indicated that the activities of nitrate reductase (NAR) had increased from 0.03 to 0.45 µmol·(min·mg)-1 while the activities of nitrite reductase (NIR) had decreased from 0.18 to 0.02 µmol·(min·mg)-1. Illumina high-throughput sequencing analysis revealed that the proportion of genus of Thauera bacteria to total microorganism increased from 0.3% (d1) to 37.27% (d64). Finally, the effluent had a total nitrogen (TN) concentration of (6.41±1.50) mg·L-1, indicating a total nitrogen removal ratio of (88.16±2.71)% and confirming the feasibility of PD+ANAMMOX in the biofilm system.

[Treatment of Medium Ammonium Wastewater by Single-stage Partial Nitritation-ANAMMOX SMBBR].

A SMBBR was established to treat medium ammonium under room temperature. Results showed that TN load can reach 0.16 kg·(m3·d)-1, and the average TN removal efficiency was (51.58±6.80)% in the SMBBR with an influent ammonia concentration of 100 mg·L-1 and DO of 0.4-0.7 mg·L-1. AOB, ANAMMOX, and NOB activity reached (2253.21±502.10) mg·(m2·d)-1, (4847.46±332.89) mg·(m2·d)-1, and (1455.17±473.83) mg·(m2·d)-1, and ANAMMOX and AOB bacteria were found to develop a good collaborative relationship. Quantitative PCR results showed that the relative abundance of ANAMMOX, AOB and NOB were 11.57%, 1.01% and 0.94%, respectively. The stable operation of single stage partial nitritation-ANAMMOX process provide an alternative technology for medium ammonia wastewater.

[Adaptability of Nitrifying Biofilm Systems to Low Temperature: MBBR and IFAS].

The long-term effects of a decreasing temperature on the nitrification performance, biofilm characteristics, and nitrifier community in a moving-bed biofilm reactor (MBBR) and integrated fixed-film activated sludge (IFAS) system were investigated at various temperatures (20, 15, and 10℃) to explore the adaptability of nitrifying biofilm systems to low temperatures. During the experiment, the extracellular polymeric substances (EPS) in the biofilms increased with decreasing temperature, which resulted in an increased biofilm mass and thickness. As there was only a biofilm phase in the MBBR to remove ammonia, the part of the carriers in the MBBR at 10℃ became plugged, which partially led to a deterioration in the effluent water quality. This indicated that the IFAS system was more adaptable to low temperatures than was the MBBR. Meanwhile, the results for the nitrifier activities showed that, although the nitrification contribution rate of the suspended phase in the IFAS system always dominated during the experiment, that of the fixed phase with regards to the ammonia uptake rate (AUR) gradually increased from 30.72% at 20℃ to 39.85% at 10℃. This indicated that the biofilm played an enhanced role in nitrification in the IFAS system. Moreover, the qPCR results revealed that the nitrifier copies of the number of biofilms increased slightly with decreased temperature, and coincided with an increase in biomass, which partially compensated for the decreased nitrification activity. These findings provide a theoretical basis for the application of the biofilm systems to wastewater treatment.

Insight into the fenton-induced degradation process of extracellular polymeric substances (EPS) extracted from activated sludge.

Although EPS in microbial aggregates are importance in successful implementation of biological wastewater treatment systems, they also exhibit detrimental role on certain circumstance, such as excess sludge dewatering. Extensive efforts have been put into the disruption of EPS for improving the dewaterability of excess sludge and Fenton's reagent treatment has been demonstrated to be a very promising sludge conditioning method for EPS destruction. However, the information regarding detailed degradation process of EPS during Fenton's reagent treatment is limited. In this study, EPS were extracted from activated sludge and treated with different concentrations of Fenton's reagent. The physicochemical characteristic changes of EPS under different treatment were investigated in terms of components, EEM, molecular weight (MW), UV-Vis and FTIR. The results showed that EPS were prone to be disintegrated, but hard to be fully mineralized. Humic substances in EPS were more resistant to Fenton's reagent than other components. Low MW components of EPS were preferentially degraded prior to the disruption of high MW components. Besides, the disintegration of EPS into lower MW ones was accompanied by the formation of higher MW compounds caused by the bridge interaction of Fe ions. The cleavage of protein's backbone in EPS was mainly through destruction of amide II (N-H and C-N) in -CO-NH-. Fenton's reagent treatment also led to a significant increase of oxygen-containing functional groups in EPS molecules. This paper may pave a path to deeply understand the mechanisms of dewatering improvements of excess sludge by Fenton's conditioning.

[Influence on Desulfurization Efficiency and Interactions of Fe/S and pH During H2S in situ Depression of High Solid Anaerobic Digestion].

To evaluate the influence of Fe/S ratio and pH on sulfide removal efficiency and interactions between Fe/S and pH, anaerobic hydrogen sulfide in situ depression tests and digested sludge liquor sulfide removal tests were carried out by using dewatering sludge from a wastewater treatment plant (WWTP). Results showed that the concentration of hydrogen sulfide in biogas from the thermal pretreatment following anaerobic digestion process could be reduced from 170.4×10-6 to 14.09×10-6 at Fe/S=7.75, which means the biogas desulfurization treatment is not required. Under the condition of pH 7.00-7.50 and Fe/S 1-11, pH is the main influencing factor for sulfide removal. Improving the pH of anaerobic digestion is beneficial in reducing the dosage of Fe(Ⅲ). An Fe/S ratio of 7.0 is the minimum to meet the biogas hydrogen sulfide emission standards during high solid sludge anaerobic digestion. The concentration of hydrogen sulfide was not up to standards if pH was below 7.30.

Composition and functional group characterization of extracellular polymeric substances (EPS) in activated sludge: the impacts of polymerization degree of proteinaceous substrates.

Characteristics of extracellular polymeric substances (EPS) in activated sludge strongly depend on wastewater substrates. Proteinaceous substrates (ProS) present in heterogeneous polymeric form are intrinsic and important parts of wastewater substrates for microorganisms in activated sludge systems. However, correlations between ProS and characteristics of EPS are scarce. This study systematically explored the impacts of monomeric (Mono-), low polymeric (LoP-) and high polymeric (HiP-) ProS on compositions and functional groups of EPS in activated sludge. The results showed that the change of polymerization degree of ProS significantly altered the composition of EPS. Compared to EPSMono-ProS, the proportion of proteins in EPSLoP-ProS and EPSHiP-ProS increased by 12.8% and 27.7%, respectively, while that of polysaccharides decreased by 22.9% and 63.6%, respectively. Moreover, the proportion of humic compounds in EPSLoP-ProS and EPSHiP-ProS were ∼6 and ∼16-fold higher than that in EPSMono-ProS, respectively. The accumulation of humic compounds in EPS increased the unsaturation degree of EPS molecules, and thereby reduced the energy requirement for electrons transition of amide bonds and aromatic groups. Size exclusion chromatography (SEC) analyses detected more molecular clusters in EPSHiP-ProS, indicating more complex composition of EPS in HiP-ProS fed activated sludge. Spectroscopic characterization revealed the dominance of hydrocarbon, protein, polysaccharide and aromatic associated bonds in all three EPS. Nevertheless, with the increase of polymerization degree of ProS, the protein associated bonds (such as CONH, CO, NC, NH) increased, while the polysaccharide associated bonds (such as COC, COH, OCOH) decreased. This paper paves a path to understand the role of ProS in affecting the production and characteristics of EPS in biological wastewater treatment systems.

Is polymeric substrate in influent an indirect impetus for the nitrification process in an activated sludge system?

Different from monomeric substrate, polymeric substrate (PS) needs to undergo slow hydrolysis process before becoming available for consumption by bacteria. Hydrolysis products will be available for the heterotrophs in low concentration, which will reduce competitive advantages of heterotrophs to nitrifiers in mixed culture. Therefore, some links between PS and nitrification process can be expected. In this study, three lab-scale sequencing batch reactors with different PS/total substrate (TS) ratio (0, 0.5 or 1) in influent were performed in parallel to investigate the influence of PS on nitrification process in activated sludge system. The results showed that with the increase of PS/TS ratio, apparent sludge yields decreased, while NO3--N concentration in effluent increased. The change of PS/TS ratio in influent also altered the cycle behaviors of activated sludge. With the increase of PS/TS ratio from 0 to 0.5 and 1, the ammonium and nitrite utilization rate increased ∼2 and 3 times, respectively. The q-PCR results showed that the abundance of nitrifiers in activated sludge for PS/TS ratio of 0.5 and 1 were 0.7-0.8 and 1.4-1.5 orders of magnitude higher than that for PS/TS ratio of 0. However, the abundance of total bacteria decreased about 0.5 orders of magnitude from the former two to the latter. The FISH observation confirmed that the nitrifiers' microcolony became bigger and more robust with the increase of PS/TS ratio. This paper paves a path to understand the role of PS/TS in affecting the nitrification process in biological wastewater treatment systems.

Nitrite oxidizing bacteria (NOB) dominating in nitrifying community in full-scale biological nutrient removal wastewater treatment plants.

Nitrification activities and microbial populations of ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) were investigated in 10 full-scale biological nutrient removal wastewater treatment plants in Xi'an, China. Aerobic batch tests were used to determine the nitrifying activities while fluorescence in situ hybridization was used to quantify the fractions of AOB and NOB in the activated sludge. The results showed that nitrifying bacteria accounted for 1-10% of the total population. Nitrosomonas and Nitrospira were the dominant bacteria for AOB and NOB respectively. Moreover, the average percentage of AOB was 1.27% and that of NOB was 4.02%. The numerical ratios of NOB/AOB varied between 1.72 and 5.87. The average ammonium uptake rate and nitrite uptake rate were 3.25 ± 0.52 mg (NH4+-N)/g(VSS) h and 4.49 ± 0.49 mg (NO2--N)/g(VSS) h, respectively. Correspondingly, the activity of NOB was 1.08-2.00 times higher than that of AOB. Thus, NOB was the dominating bacteria in nitrifying communities. The year-round data of Dianzicun (W6) also expressed a similar trend. Since NOB had higher activities than that of AOB, a large nitrite oxidation pool could be formed, which guaranteed that no nitrite would be accumulated. Therefore, stable nitrification could be achieved. A conceptual model was proposed to describe the population variation of AOB and NOB in a nitrifying community.

[Enrichment of Nitrospira in Activated Sludge and Kinetic Characterization].

Nitrospira was enriched from activated sludge by using fed-batch cultivation, and its related kinetic characterization was studied. The results showed that Nitrospira could be successfully enriched from the activated sludge for a controlled nitrite concentration no higher than 2 mg·L-1. The maximum nitrate oxidation rate was 48.72 mg·(g·h)-1. The fluorescence for the in situ hybridization results showed that Nitrospira accounted for about 75% of the total biomass, while Nitrobacter accounted for only 0.1%. In addition, the kinetic parameters of Nitrospira at 20℃ were also investigated. The results showed that the optimum growth temperature for Nitrospira was 30-35℃. The temperature correction coefficient τN was 1.046. The nitrite half-saturation constant KS and oxygen half-saturation constant KO were (0.32±0.03)mg·L-1 and (1.52±0.09)mg·L-1, respectively. This study on the kinetic characterization of Nitrospira provided a theoretical foundation for the treatment plant design and process optimization.

[Fast Start-up of ANAMMOX and the Spatial Distribution of EPS in ANAMMOX Granules].

An anaerobic sequencing batch reactor(ASBR) inoculated with activated sludge was employed to investigate the start-up of anaerobic ammonium oxidation(ANAMMOX) process and the spatial distribution of extracellular polymeric substances(EPS) in ANAMMOX granules. The results showed that the removal rates of NH4+-N and NO2--N reached more than 99%. The removal rate of total nitrogen(TN) was 89.87%±0.43% and the TN removal load in the ASBR was 1.7 kg·(m3·d)-1. The ratios of nitrite consumption and nitrate production to ammonium consumption were 1.32±0.08 and 0.24±0.03, respectively. Besides, the pH and the effluent nitrate concentration in bulk liquid were considered as two simple indicators for rapid diagnosis of ANAMMOX performance. The proteins(PN) was the main component of EPS in ANAMMOX granular sludge. The PN and polysaccharides(PS) in ANAMMOX granules were (59.61±5.64) mg·g-1 and (12.21±2.04) mg·g-1, respectively, with the ratio of PN/PS reaching approximately 4.88±1.39. ß-D-glucofuranose and dead cells were distributed in the outermost layer of granules, while living cells, PN, lipids, α-glucosamine and α-mannose were distributed throughout the granules and mainly concentrated on the outside of granules. PN and lipids constituted the framework of ANAMMOX granules and ANAMMOX bacteria were embedded among the PN and lipids matrix.

[Comparison of Operating Performance of Partial Nitritation Systems with Two Different Inhibition Strategies].

Two SBRs which were under high ammonia loading[1 kg·(m3·d)-1] and different dual inhibition with feed-batch were employed to study how to control the stability of partial nitritation system. The experimental result showed that the dual inhibition of FNA and DO or FA and DO could implement partial nitrification process at 35℃±1℃ and the ammonia concentration of 1000 mg·L-1. The effluent NO2--N/NH4+-N ratio was about 1, and the effluent NO3--N concentration was close to 0, which was suitable for the appropriate influent for the ANAMMOX. In R1, under the dual inhibition of high FA and low DO concentration, the nitrite oxidizing rate was reduced from 28.16 mg·(g·h)-1 to 0.3 mg·(g·h)-1 (calculated as NO2--N, the same as below). The ammonia oxidizing rate decreased by 43.60%, which was stable at about 20 mg·(g·h)-1 (calculated as NH4+-N, the same as below). In R2,under the dual inhibition of high FNA and low DO concentration, the nitrite oxidizing rate reduced from 12.37 mg·(g·h)-1 to 0.02 mg·(g·h)-1. But the ammonia oxidizing rate remained at a higher level[45 mg·(g·h)-1]. Comparing the nitrification performance of the two SBRs under different control strategies, the dual inhibition of high FNA and low DO concentration had the advantages of short cultivation period, high biological activity and stable operation. It is therefore more suitable for the achievement of the partial nitrification.

[Non-CO2 Greenhouse Gas Release from Different Biological Wastewater Treatment Processes].

Methane (CH4) and nitrous oxide (N2O) are two of the most important non-CO2 greenhouse gases. And municipal sewage treatment plant is an important anthropogenic source of CH4 and N2O. Therefore, it is essential to measure the production and emission of CH4 and N2O during biological wastewater treatment process. The surface emission flux isolation chamber was employed to collect the gas sample from the Xi'an No.3 WWTP (the Orbal oxidation ditch process) and Xi'an NO.4 WWTP (A/A/O process) to determine the contents of methane and nitrous oxide. And the effects of temperature and dissolved oxygen concentration on non-CO2 greenhouse gases emission from Xi'an NO.4 WWTP were discussed. The results showed that methane and nitrous oxide emission factors from No.3 WWTP were 1181 mg CH4 per m3 influent and 36.20 mg N2O per m3 influent, respectively while those from the No.4 WWTP were 209 mg CH4 per m3 influent and 54.64 mg N2O per m3 influent. In addition, the important influencing factors which affected methane and nitrous oxide emission were temperature, aeration strategy, DO, nitrite oxidation rate and specific methanogenic activity.

[Effect of Temperature on PAO Activity and Substrate Competition].

To investigate the effect of temperature on the activity of high-temperature phosphate accumulating organisms (PAOHT) and their competitive ability for the substrate, the sludge from an enhanced biological phosphorus removal (EBPR) reactor stably operated at the high temperature of 30℃ was used. The results showed that PAOHT activity and their competitive ability for the substrate increased with temperature increasing from 15℃ to 30℃. When the temperature was as higher as 30℃, the rates of anaerobic phosphorus release, aerobic phosphorus uptake and acetate uptake of PAOHT were 239.46 mg·(g·h)-1, 79.90 mg·(g·h)-1, 357.47 mg·(g·h)-1, respectively. The corresponding value of ΔP/ΔHAc was 0.628, which was considerably higher than that of PAO reported in literatures. A simplified Arrhenius equation was used to describe the effect of temperature on the rates of anaerobic phosphorus release, aerobic phosphorus uptake and acetate uptake, and the temperature coefficients were 1.08, 1.07 and 1.05, respectively.

[Community Structure and Activity Analysis of the Nitrifiers in Raw Sewage of Wastewater Treatment Plants].

The communities and activity of nitrifiers collected from the raw sewage of the 2nd and 3rd wastewater treatment plants (WWTP) in Xi'an were investigated. FISH results indicated that the (AOB+NOB)/EUB percentages were (5.35±2.1)% and(6.0±2.8)% in the 2nd and 3rd WWTP, respectively. The dominant AOB was Nitrosomonas europaea/Nitrosococcus mobilis lineage and the dominant NOB was Nitrospira, the sub-dominant NOB was Nitrobacter, and coexisted with Nitrococcus, Nitrospina. Respirometric assays showed that the influent nitrifiers were active following a 2-16 hour period of metabolic induction. The ammonium utilized rate was (0.32±0.12) mg·(L·h)-1 and (0.43±0.17) mg·(L·h)-1, nitrite utilized rate was (0.71±0.18) mg·(L·h)-1 and (0.58±0.27) mg·(L·h)-1 for nitrifers in raw sewage fed to the 2nd and 3rd WWTP, respectively. Therefore, nitrifiers were present and active in the raw sewage, and played the role of natural continuous seeding in the activated sludge system. Based on the nitrification activity, the estimated continuous seeding intensity of AOB and NOB was 0.08-0.09 g·(g·d)-1 and 0.11-0.24 g·(g·d)-1, respectively.

[Effects of carbon sources, temperature and electron acceptors on biological phosphorus removal].

Effects of carbon sources, temperature and electron acceptors on phosphorus uptake and release were investigated in a pilot-scale oxidation ditch. Phosphorus uptake and release rates were measured with different carbon sources (domestic sewage, sodium acetate, glucose) at 25 degrees C. The results showed that the minimum phosphorus uptake and release rates of glucose were 5.12 mg x (g x h)(-1) and 6.43 mg x (g x h)(-1), respectively, and those of domestic sewage are similar to those of sodium acetate. Phosphorus uptake and release rates increased with the increase of temperature (12, 16, 20 and 25 degrees C) using sodium acetate as carbon sources. Anoxic phosphorus uptake rate decreased with added COD. Electron acceptors (oxygen, nitrate, nitrite) had significant effects on phosphorus uptake rate and their order was in accordance with oxygen > nitrate > nitrite. The mass ratio of anoxic P uptake and N consumption (P(uptake)/N (consumption)) of nitrate and nitrite were 0.96 and 0.65, respectively.

[Transformation characteristics of carbon, nitrogen, phosphorus and sulfur during thermal hydrolysis pretreatment of sludge with high solid content].

The transformation characteristics of carbon, nitrogen, phosphorus and sulfur in dewatering sludge from municipal wastewater treatment plant (WWTP) were investigated after thermal hydrolysis pretreatment at 165 degress C for 50 min. The results showed that the hydrolysis efficiency of VSS could reach as high as 43.35%, 54.36% of protein and 65.12% of carbohydrate were transferred to dissolved organics, respectively, and the main component of dissolved organic matter in hydrolysate was dissolved protein (52.18% ), 54.23% of insoluble organic nitrogen was turned into dissolved nitrogen and 22.13% of dissolved nitrogen in hydrolysate was converted to ammonia. The transformation rate of insoluble phosphorus was 30.52%. Dissolved phosphorus was mostly transformed to phosphate (79.84%) as phosphorus-accumulating bacteria cells were crushed. 50.03% of insoluble organic sulfur was hydrolyzed, and little change was detected in sulfide (0.50%). The analysis results of the organic compounds transformation are valuable for treatment of the thermal hydrolysis pretreated sludge with high solid content.

Nutrient release, recovery and removal from waste sludge of a biological nutrient removal system.

The uncontrolled release of nutrients from waste sludge results in nitrogen and phosphorus overloading in wastewater treatment plants when supernatant is returned to the inlet. A controlled release, recovery and removal of nutrient from the waste sludge of a Biological Nutrient Removal system (BNR) are investigated. Results showed that the supernatant was of high mineral salt, high electrical conductivity and poor biodegradability, in addition to high nitrogen and phosphorus concentrations after the waste sludge was hydrolysed through sodium dodecyl sulphate addition. Subsequently, over 91.8% of phosphorus and 10.5% of nitrogen in the supernatants were extracted by the crystallization method under the conditions of 9.5 pH and 400 rpm. The precipitate was mainly struvite according to X-ray diffraction and morphological examination. A multistage anoxic-oxic Moving Bed Biofilm Reactor (MBBR) was then adopted to remove the residual carbon, nitrogen and phosphorus in the supernatant. The MBBR exhibited good performance in simultaneously removing carbon, nitrogen and phosphorus under a short aeration time, which accounted for 31.25% of a cycle. Fluorescence in situ hybridization analysis demonstrated that nitrifiers presented mainly in floc, although higher extracellular polymeric substance content, especially DNA, appeared in the biofilm. Thus, a combination of hydrolysis and precipitation, followed by the MBBR, can complete the nutrient release from the waste sludge of a BNR system, recovers nutrients from the hydrolysed liquor and removes nutrients from leftovers effectively.

A new classification paradigm of extracellular polymeric substances (EPS) in activated sludge: separation and characterization of exopolymers between floc level and microcolony level.

Extracellular polymeric substances (EPS) play a crucial role in the formation of activated sludge flocs. However, until now, the EPS are rather classified by the method used for extraction than by a theoretical consideration of their function and composition. In this paper, a new classification paradigm of EPS was proposed, which offered a novel approach to identify the role of EPS in the formation of activated sludge flocs. The current study gave an exploration to distinguish the EPS in the floc level (extra-microcolony polymers, EMPS) and in the microcolony level (extra-cellular polymers, ECPS). It was found that cation exchange resin treatment is efficient to disintegrate the flocs for EMPS extraction, however, inefficient to disaggregate the microcolonies for ECPS harvesting. A two-steps extraction strategy (cation exchange resin treatment followed by ultrasonication-high speed centrifugation treatment) was suggested to separate these two types of EPS in activated sludge flocs and the physicochemical characteristics of EMPS and ECPS were compared. The protein/polysaccharide ratio of ECPS was higher than that of EMPS and the molecular weight of proteins in EMPS and ECPS were found to be different. The ECPS contained higher molecular weight proteins and more hydrophobic substances than the EMPS contained. The result of excitation-emission matrix fluorescence spectroscopy analysis also showed that the EMPS and the ECPS have different fluorescent expressions and the components of EMPS were more diverse than that of ECPS. All results reported herein demonstrated that two different types of exopolymers exist in the activated sludge flocs and the inter-particle forces for aggregation of activated sludge flocs are not identical between the floc level and the microcolony level. It suggested that cation bridging interactions are more crucial in floc level flocculation, while the entanglement and hydrophobic interactions are more important in microcolony level cohesion.

The important implications of particulate substrate in determining the physicochemical characteristics of extracellular polymeric substances (EPS) in activated sludge.

Since the notable amount of particulate substrate in wastewater, the implications of particulate substrate on treatment efficiency have been a topic of major interest in the field of biological wastewater treatment. The particulate substrate has to be hydrolyzed by the extracellular enzymes, which are mainly embedded in extracellular polymeric substances (EPS) matrix of microbial aggregates, prior to consumption. Therefore, the important relevance between the particulate substrate and the characteristics of EPS can be expected. In this study, two lab-scale sequencing batch reactors were performed in parallel to investigate the effects of particulate and soluble substrate on the physicochemical characteristics of EPS in activated sludge. The results showed that the particulate substrate in the influent could significantly change the properties of activated sludge and the characteristics of EPS. More open and fluffy flocs with poorer settleability and dewaterability were formed with particulate substrate. More protein and humic compounds were introduced into the EPS matrix due to the deep involvement of protein and humic compounds in hydrolysis process of particulate substrate. The increments of protein and humic compounds then caused the slight higher molecular weight, higher hydrophobicity and lower zeta potential of EPS in particulate substrate system. The results in this study permitted for obtaining answers to understand the significant implications of particulate substrate in determining the physicochemical characteristics of EPS in biological wastewater treatment systems.

Hydrogen utilization rate: A crucial indicator for anaerobic digestion process evaluation and monitoring.

Hydrogenotrophic methanogens had been considered as key species for the anaerobic digestion (AD) of industrial wastewater and municipal sludge. However, how to evaluate the activity of the hydrogenotrophic methanogens was less studied. In this study, a volumetric device and a test procedure were developed for measuring the specific hydrogen utilization rate (HUR) of anaerobic sludge. Results showed that HUR values were highly influenced by sludge concentrations because of limitation on H2 mass transfer. The critical value of sludge concentration in the test bottle should not be higher than 1 gVSS/L. Under such condition, the kinetics of HUR would not be limited by H2 mass transfer and the maximal value of HUR could be obtained. Field survey confirmed that HUR exhibits a good relationship with specific methanogenic activity (SMA) and reactor performance. An anaerobic system with a relatively high HUR was found to be beneficial for maintaining H2 partial pressure in an appropriately low level. Moreover, such system was thermodynamically favourable for the syntrophic degradation of volatile fatty acids. As a crucial parameter of the anaerobic process, HUR could be used as a key indicator for evaluating and monitoring AD processes.