Potential Role of the Anammoxosome in the Adaptation of Anammox Bacteria to Salinity Stress.

The underlying adaptative mechanisms of anammox bacteria to salt stress are still unclear. The potential role of the anammoxosome in modulating material and energy metabolism in response to salinity stress was investigated in this study. The results showed that anammox bacteria increased membrane fluidity and decreased mechanical properties by shortening the ladderane fatty acid chain length of anammoxosome in response to salinity shock, which led to the breakdown of the proton motive force driving ATP synthesis and retarded energy metabolism activity. Afterward, the fatty acid chain length and membrane properties were recovered to enhance the energy metabolic activity. The relative transmission electron microscopy (TEM) area proportion of anammoxosome decreased from 55.9 to 38.9% under salinity stress. The 3D imaging of the anammox bacteria based on Synchrotron soft X-ray tomography showed that the reduction in the relative volume proportion of the anammoxosome and the concave surfaces was induced by salinity stress, which led to the lower energy expenditure of the material transportation and provided more binding sites for enzymes. Therefore, anammox bacteria can modulate nitrogen and energy metabolism by changing the membrane properties and morphology of the anammoxosome in response to salinity stress. This study broadens the response mechanism of anammox bacteria to salinity stress.

The recovery potential and utilization pathway of chemical energy from wastewater pollutants during wastewater treatment in China.

Research on the potential for chemical energy recovery and the optimization of recovery pathways in different regions of China is still lacking. This study aimed to address this gap by evaluating the potential and optimize the utilization pathways for chemical energy recovery in various regions of China for achieving sustainable wastewater treatment. The results showed that the eastern and northeastern regions of China exhibited higher chemical energy levels under the existing operating conditions. Key factors affecting chemical energy recovery included chemical oxygen demand removal (ΔCOD), treatment scale, and specific energy consumption (µ) of wastewater treatment plants (WWTPs). Furthermore, the average improvement in the chemical energy recovery rate with an optimized utilization pathway was approximately 40% in the WWTPs. The use of the net-zero energy consumption (NZE) model proved effective in improving the chemical energy recovery potential, with an average reduction of greenhouse gas (GHG) emissions reaching next to 95% in the investigated WWTPs.

The acceleration of aerobic sludge granulation by alternating organic loading rate: Performance and mechanism.

As a highly promising treatment technology for wastewater, long start-up time is one of the bottlenecks hindering the widespread application of aerobic granular sludge (AGS). This study focused on exploring the possibility of alternating organic loading rate (OLR) in promoting AGS granulation. Under alternating OLR (3.6-14.4 kgCOD/m3·d), AGS granulation was significantly accelerated. The mean granule size under alternating load reached 234.6 µm at 17 d, while under constant OLR (7.2 kgCOD/m3·d), the mean granule size was only 179.2 µm. Moreover, the granule size maintained continuous growth even when the alternating OLR was changed to constant OLR. Alternating load significantly increased the content of extracellular polymeric substances (EPS), especially proteins (PN) in tightly bound EPS (TB-EPS), which was likely the main reason for accelerating AGS granulation. Moreover, alternating load reduced the hydrophilicity of EPS and promoted the content of proteins secondary structures that favored aggregation in TB-EPS, which were also beneficial for granulation. Microbial community results showed that alternating load might promote the enrichment of EPS producing bacteria, such as Thauera, Brevundimonas and Shinella. Meanwhile, the content of enzymes that regulated amino acids metabolism also increased under alternating load, which might be related to the increase of PN in EPS. These results further demonstrated that alternating load promoted granulation through EPS.

Fate of iron nanoparticles in anammox system: Dissolution, migration and transformation.

Iron nanoparticles (FeNPs) are commonly used in various industrial processes, leading to their release into the environment and eventual entrance into wastewater treatment plants (WWTPs). FeNPs undergo dissolution, migration, and transformation in WWTPs, which can potentially affect the stable operation of anaerobic ammonia oxidation (anammox) systems and may be discharged with wastewater or biomass. To better understand the fate of FeNPs in anammox systems, exposure experiments were conducted using anammox granular sludges (AnGS) and FeNPs. Results demonstrated that FeNPs released Fe2+ upon contact with water, with a portion being bound to functional groups in extracellular polymeric substances (EPS) and the rest entering the bacteria to form highly absorbable substances. A significant amount of FeNPs was observed to cover the surface of AnGS or aggregate and deposit at the bottom of the reactor, eventually converting into Fe3O4 and stably existing within the anammox system. The findings of this study clarify the fate of FeNPs in anammox systems and provide important insights into the stable operation of anammox systems under FeNPs exposure.

Cyanophycin Granule Polypeptide: a Neglected High Value-Added Biopolymer, Synthesized in Activated Sludge on a Large Scale.

Recovery of microbial synthetic polymers with high economic value and market demand in activated sludge has attracted extensive attention. This work analyzed the synthesis of cyanophycin granule peptide (CGP) in activated sludge and its adsorption capacity for heavy metals and dyes. The distribution and expression of synthetic genes for eight biopolymers in two wastewater treatment plants (WWTPs) were analyzed by metagenomics and metatranscriptomics. The results indicate that the abundance and expression level of CGP synthase (cphA) are similar to those of polyhydroxyalkanoate polymerase, implying high synthesis of CGP in activated sludges. CGP in activated sludge is mainly polymerized from aspartic acid and arginine, and its secondary structure is mainly ß-sheet. The crude yields of CGP are as high as 104 ± 26 and 76 ± 13 mg/g dry sludge in winter and in summer, respectively, comparable to those of polyhydroxyalkanoate and alginate. CGP has a stronger adsorption capacity for anionic pollutants (Cr (VI) and methyl orange) than for cationic pollutants because it is rich in guanidine groups. This study highlights prospects for recovery and application of CGP from WWTPs. IMPORTANCE The conversion of organic pollutants into bioresources by activated sludge can reduce the carbon dioxide emission of wastewater treatment plants. Identification of new high value-added biopolymers produced by activated sludge is beneficial to recover bioresources. Cyanophycin granule polypeptide (CGP), first discovered in cyanobacteria, has unique chemical and material properties suitable for industrial food, medicine, cosmetics, water treatment, and agriculture applications. Here, we revealed for the first time that activated sludge has a remarkable ability to produce CGP. These findings could further facilitate the conversion of wastewater treatment plants into resource recycling plants.

A new pattern of the partial nitrification and Anammox immobilized gel beads: core-shell embedded carrier.

Single-stage partial nitrification and Anammox (PN/A) is an efficient and energy-saving denitrification process for wastewater. However, its application is limited by the growth conditions of microorganisms. Therefore, we improved the PN/A by developing a novel core-shell embedded carrier. With Anammox gel as the core and Ammonia-oxidizing bacteria gel as the shell, these beads can achieve dissolved oxygen partitioning and provide a suitable environment for the growth of different bacteria. On this basis, the influence of the shape of core-shell embedded gel on nitrogen removal performance was systematically studied, and the internal morphology and pore size of gel beads were characterized. The results showed that the nitrogen removal efficiency of spherical and square gels was increased by 33.70% and 13.47%, respectively, in the batch test. Fluorescence in situ hybridization confirmed the stratified growth of ammonia-oxidizing bacteria and Anammox in carriers, and the relative abundance value of the two bacteria were 1.25:1 and 1.43:1, respectively. Although the mechanical strength of square gel beads is slightly higher than that of spherical, spherical gel is considered the most suitable gel shape due to its small pore size and poor pore connectivity, which ensures the matching of internal Anammox and external PN reaction. In the long-term experiment, the core-shell embedded beads still had the design characteristics, and the TN removal efficiency was increased by 36.25% despite occasional oxygen excess.

A full-view management method based on artificial neural networks for energy and material-savings in wastewater treatment plants.

Carbon neutrality has been received extensive attention in the field of wastewater treatment. The optimal management of wastewater treatment plants (WWTPs) has great significance and urgency since the serious energy and materials waste. In this study, a full-view management method based on artificial neural networks (ANNs) for energy and material savings in WWTPs was established. More than 5 years of historical operating data from two typical plants (size 40,000 t/d and 10,000 t/d) located in Chongqing, China, were obtained, and public data in the service area of each plant were systematically collected from open channels. These abundant historical and public data were used to train two ANNs (GRA-CNN-LSTM model and PCA-BPNN model) to predict the inlets/outlets wastewater quality and quantity. The overall average prediction accuracy of inlets/outlets wastewater indicators are greater than 92.60% and 93.76%, respectively. By combining the two models, more appropriate process operation strategies can be obtained 2 weeks in advance, with more than 11.20% and 16.91% reduction of energy and material costs, respectively. This proposed method can provide full-view decision support for the optimal management of WWTPs and is also expected to support carbon emission control and carbon neutrality in the field of wastewater treatment.

The GHG mitigation opportunity of sludge management in China.

Greenhouse gas (GHG) mitigation in wastewater treatment sector is indispensable in China's carbon neutral target. As an important component of wastewater system, sludge generation is rapidly increased with the acceleration of urbanization in China. It is crucial to investigate the carbon footprint of various sludge management strategies and quantify the potential optimization of GHG reduction effect at national scale. Therefore, this study conducted a comprehensive analysis of sludge distribution and GHG profiles of various sludge systems. The overall dry sludge generation in China is 12.15 Mt, with spatial resolution at city level. Different sludge treatment options were categorized into four types: energy recovery, nutrient recovery (e.g. phosphorus and nitrogen), material valorisation (e.g. brick, biochar) and conventional disposal. With various sludge treatment options, the GHG profile of annual sludge management in China ranges from -35.86 Mt/year to 57.11 Mt/year. The best GHG mitigation can be achieved through energy recovery by co-incineration system and the greatest reduction opportunity is concentrated in highly urbanized regions, such as Yangtze River Delta, Pearl River Delta, and Beijing-Tianjin-Hebei urban agglomerations.

Adaptation mechanism of aerobic denitrifier Enterobacter cloacae strain HNR to short-term ZnO nanoparticle stresses.

The adaptation mechanism of a wild type (WT) and resistant type (Re) strain of the aerobic denitrifier Enterobacter cloacae strain HNR to short-term ZnO nanoparticle (NP) stresses was investigated. The results showed that Re maintained higher nitrite reductase (NIR) and nitrate reductase (NR) activities and showed lower increment of reactive oxygen species (ROS) than WT, under ZnO NP stresses. The affinity constant (KA) of WT to Zn2+ was 5.06 times that of Re, indicating that Re was more repulsive to Zn2+ released by ZnO NPs. Transcriptomic analysis revealed that the up-regulation of the nitrogen metabolism of Re helped maintain NIR and NR activities, that the enhancement of purine metabolism lowered the intracellular ROS increment, and that the up-regulation of cationic antimicrobial peptide resistance contributed to the lower KA of Re to Zn2+. These findings provided new insights into the adaptation mechanism of aerobic denitrifying bacteria to ZnO NPs.

Quantitative three-dimensional nondestructive imaging of whole anaerobic ammonium-oxidizing bacteria.

Anaerobic ammonium-oxidizing (anammox) bacteria play a key role in the global nitrogen cycle and in nitrogenous wastewater treatment. The anammox bacteria ultrastructure is unique and distinctly different from that of other prokaryotic cells. The morphological structure of an organism is related to its function; however, research on the ultrastructure of intact anammox bacteria is lacking. In this study, in situ three-dimensional nondestructive ultrastructure imaging of a whole anammox cell was performed using synchrotron soft X-ray tomography (SXT) and the total variation-based simultaneous algebraic reconstruction technique (TV-SART). Statistical and quantitative analyses of the intact anammox bacteria were performed. High soft X-ray absorption composition inside anammoxosome was detected and verified to be relevant to iron-binding protein. On this basis, the shape adaptation of the anammox bacteria response to iron was explored.

Underlying mechanisms of ANAMMOX bacteria adaptation to salinity stress.

Dealing with nitrogen-rich saline wastewater produced by industries remains challenging because of the inhibition of functional microorganisms by high salinity. The underlying mechanisms of anaerobic ammonium-oxidizing bacteria (AnAOB) exposed to salinity stress should be studied to investigate the potential of anaerobic ammonium oxidation (ANAMMOX) for applications in such wastewater. In this study, the total DNA from granular sludge was extracted from an expanded granular sludge bed (EGSB) reactor operated at 0, 15 and 30 g/L salinity and subjected to high-throughput sequencing. The nitrogen removal performance in the reactor could be maintained from 86.2 to 88.0% at less than 30 g/L salinity level. The microbial diversity in the reactor under saline conditions was lower than that under the salt-free condition. Three genera of AnAOB were detected in the reactor, and Candidatus Kuenenia was the most abundant. The predictive functional profiling based on the Clusters of Orthologous Groups of proteins (COGs) database showed that the inhibition of AnAOB under saline conditions was mainly characterised by the weakening of energy metabolism and intracellular repair. AnAOB might adapt to salinity stress by increasing their rigidity and intracellular osmotic pressure. The predictive functional profiling based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database revealed that the inhibition of AnAOB was mainly manifested by the weakening of intracellular carbohydrate and lipid metabolism, the blockage of intracellular energy supply and the reduction of membrane transport capacity. AnAOB might adapt to salinity stress by strengthening wall/membrane synthesis, essential cofactors (porphyrins) and energy productivity, enhancing intracellular material transformation and gene repair and changing its structure and group behaviour. The stability of the nitrogen removal performance could be maintained via the adaptation of AnAOB to salinity and their increased abundance.

Fetal Serum Metabolites Are Independently Associated with Gestational Diabetes Mellitus.

BACKGROUND/AIMS: Gestational diabetes (GDM) might be associated with alterations in the metabolomic profile of affected mothers and their offspring. Until now, there is a paucity of studies that investigated both, the maternal and the fetal serum metabolome in the setting of GDM. Mounting evidence suggests that the fetus is not just passively affected by gestational disease but might play an active role in it. Metabolomic studies performed in maternal blood and fetal cord blood could help to better discern distinct fetal from maternal disease interactions. METHODS: At the time of birth, serum samples from mothers and newborns (cord blood samples) were collected and screened for 163 metabolites utilizing tandem mass spectrometry. The cohort consisted of 412 mother/child pairs, including 31 cases of maternal GDM. RESULTS: An initial non-adjusted analysis showed that eight metabolites in the maternal blood and 54 metabolites in the cord blood were associated with GDM. After Benjamini-Hochberg (BH) procedure and adjustment for confounding factors for GDM, fetal phosphatidylcholine acyl-alkyl C 32: 1 and proline still showed an independent association with GDM. CONCLUSIONS: This study found metabolites in cord blood which were associated with GDM, even after adjustment for established risk factors of GDM. To the best of our knowledge, this is the first study demonstrating an independent association between fetal serum metabolites and maternal GDM. Our findings might suggest a potential effect of the fetal metabolome on maternal GDM.

Dynamic Dispersal of Surface Layer Biofilm Induced by Nanosized TiO2 Based on Surface Plasmon Resonance and Waveguide.

Pollutant degradation is present mainly in the surface layer of biofilms, and the surface layer is the most vulnerable to impairment by toxic pollutants. In this work, the effects of nanosized TiO2 (n-TiO2) on the average thicknesses of Bacillus subtilis biofilm and on bacterial attachment on different surfaces were investigated. The binding mechanism of n-TiO2 to the cell surface was also probed. The results revealed that n-TiO2 caused biofilm dispersal and the thicknesses decreased by 2.0 to 2.6 µm after several hours of exposure. The attachment abilities of bacteria with extracellular polymeric substances (EPS) on hydrophilic surfaces were significantly reduced by 31% and 81% under 10 and 100 mg/liter of n-TiO2, respectively, whereas those of bacteria without EPS were significantly reduced by 43% and 87%, respectively. The attachment abilities of bacteria with and without EPS on hydrophobic surfaces were significantly reduced by 50% and 56%, respectively, under 100 mg/liter of n-TiO2 The results demonstrated that biofilm dispersal can be attributed to the changes in the cell surface structure and the reduction of microbial attachment ability.IMPORTANCE Nanoparticles can penetrate into the outer layer of biofilm in a relatively short period and can bind onto EPS and bacterial surfaces. The current work probed the effects of nanosized TiO2 (n-TiO2) on biofilm thickness, bacterial migration, and surface properties of the cell in the early stage using the surface plasmon resonance waveguide mode. The results demonstrated that n-TiO2 decreased the adhesive ability of both cell and EPS and induced bacterial migration and biofilm detachment in several hours. The decreased adhesive ability of microbes and EPS worked against microbial aggregation, reducing the effluent quality in the biological wastewater treatment process.

Fetal But Not Maternal Angiotensin Converting Enzyme (ACE)-2 Gene Rs2074192 Polymorphism is Associated with Increased Risk of Being a Small For Gestational Age (SGA) Newborn.

BACKGROUND/AIMS: The maternal and fetal Renin-Angiotensin-System is involved in the control of pregnancy outcomes such as blood pressure control and gestational age. However, very little is known about the impact of the angiotensin converting enzyme 2 (ACE2) on pregnancy outcome. We thus performed a prospective clinical observational study analyzing the association of maternal and fetal ACE2 gene rs2074192 polymorphism with fetal growth during pregnancy. METHODS: 898 singleton pregnant women were prospectively recruited. 739 pregnant women finally participated in the study and were genotyped. 474 women also donated umbilical cord blood for gene analysis of their offspring. All data such as basic demographic information, data from birth records, biochemical and immunological parameters, as well as Doppler ultrasonographic findings during pregnancy were collected. Fetal and maternal ACE2 gene rs2074192 polymorphism was genotyped by DNA sequencing. RESULTS: Our analysis showed that the maternal ACE2 gene rs2074192 polymorphism was not associated with gestational hypertension, gestational diabetes mellitus, anemia, postpartum hemorrhage and fetal growth. However, neonates having rs2074192 T allele were more likely to be born as small for gestational age (SGA) babies. After multivariable logistic regression considering known confounding, we could demonstrate that the neonatal rs2074192 T allele was an independent risk factor for SGA (OR: 22.93, 95%CI: 1.26∼418.77, P< 0.05). CONCLUSION: This is the first study showing that the babies but not their mothers with ACE2 gene rs2074192 T allele had a high risk for SGA, which contributes to metabolic syndrome and cardiovascular diseases in later life.

Net-Zero-Energy Model for Sustainable Wastewater Treatment.

A large external energy input prevents wastewater treatment from being environmentally sustainable. A net-zero-energy (NZE) wastewater treatment concept based on biomass energy recycling was proposed to avoid wasting resources and to promote energy recycling in wastewater treatment plants (WWTPs). Simultaneously, a theoretical model and boundary condition based on energy balance were established to evaluate the feasibility of achieving NZE in WWTPs; the model and condition were employed to analyze data from 20 conventional WWTPs in China. A total of six WWTPs can currently export excess energy, eight WWTPs can achieve 100% energy self-sufficiency by adjusting the metabolic material allocation, and six municipal WWTPs cannot achieve net-zero energy consumption based on the evaluation of the theoretical model. The NZE model offset 79.5% of the electricity and sludge disposal cost compared with conventional wastewater treatment. The NZE model provides a theoretical basis for the optimization of material regulation for the effective utilization of organic energy from wastewater and promotes engineering applications of the NZE concept in WWTPs.

A Systematic Review and Meta-Analysis of Influenza A Virus Infection During Pregnancy Associated with an Increased Risk for Stillbirth and Low Birth Weight.

BACKGROUND/AIMS: Impaired pregnancy outcomes, such as low birth weight are associated with increased disease risk in later life, however little is known about the impact of common infectious diseases during pregnancy on birth weight. The study had two aims: a) to investigate risk factors of influenza virus infection during pregnancy, and b) to analyze the impact of influenza virus infection on pregnancy outcome, especially birth weight. METHODS: Prospective and retrospective observational studies found in PubMed, MEDLINE, Embase, Google Scholar, and WangFang database were included in this meta analysis. Data of included studies was extracted and analyzed by the RevMan software. RESULTS: Pregnant women with anemia (P=0.004, RR=1.46, 95% CI: 1.13-1.88), obesity (P<0.00001, RR=1.35, 95% CI: 1.25-1.46) and asthma (P<0.00001, RR=1.99, 95% CI: 1.67-2.37) had higher rates of influenza virus infection. Regarding birth outcomes, influenza A virus infection did not affect the likelihood for cesarean section. Mothers with influenza had a higher rate of stillbirth (P=0.04, RR=2.36, 95% CI: 1.05-5.31), and their offspring had low 5-minute APGR Scores (P=0.009, RR=1.39, 95% CI: 1.08-1.79). Furthermore, the rate for birth weight < 2500g (P=0.04, RR=1.71, 95% CI: 1.03-2.84) was increased. CONCLUSION: Results of this study showed that anemia, asthma and obesity during pregnancy are risk factors influenza A virus infection during pregnancy. Moreover, gestational influenza A infection impairs pregnancy outcomes and increases the risk for low birth weight, a known risk factor for later life disease susceptibility.

Changes in the osmolarity of the embryonic microenvironment induce neural tube defects.

Many maternal disorders that modify the embryonic microenvironment, such as a change in osmolarity, can affect development, but how these changes influence the early embryo remains obscure. Neural tube defects, for example, are common congenital disorders found in fetus and neonates. In this study, we investigated the impact of anisotonic osmolarity (unequal osmotic pressures) on neural tube development in the early chick embryo, finding that neuronal cell differentiation was impaired in the neural tube due to enhanced apoptosis and repressed cell proliferation. Anisotonic osmolarity also affected normal development of the neural crest, which in turn influenced abnormal development of the neural tube. As neural tube development is highly dependent on the proper expression of bone morphogenetic protein 4 (BMP4), paired box 7 (PAX7), and sonic hedgehog (SHH) genes in the dorsal and ventral regions along the tube, we investigated the impact of anisotonic osmolarity on their expression. Indeed, small changes in osmolarity could positively and negatively impact the expression of these regulatory genes, which profoundly affected neural tube development. Thus, both the central and peripheral nervous systems were perturbed by anisotonic consitions as a consequence of the abnormal expression of key genes within the developing neural tube.

The impact of high-salt exposure on cardiovascular development in the early chick embryo.

In this study, we show that high-salt exposure dramatically increases chick mortality during embryo development. As embryonic mortality at early stages mainly results from defects in cardiovascular development, we focused on heart formation and angiogenesis. We found that high-salt exposure enhanced the risk of abnormal heart tube looping and blood congestion in the heart chamber. In the presence of high salt, both ventricular cell proliferation and apoptosis increased. The high osmolarity induced by high salt in the ventricular cardiomyocytes resulted in incomplete differentiation, which might be due to reduced expression of Nkx2.5 and GATA4. Blood vessel density and diameter were suppressed by exposure to high salt in both the yolk sac membrane (YSM) and chorioallantoic membrane models. In addition, high-salt-induced suppression of angiogenesis occurred even at the vasculogenesis stage, as blood island formation was also inhibited by high-salt exposure. At the same time, cell proliferation was repressed and cell apoptosis was enhanced by high-salt exposure in YSM tissue. Moreover, the reduction in expression of HIF2 and FGF2 genes might cause high-salt-suppressed angiogenesis. Interestingly, we show that high-salt exposure causes excess generation of reactive oxygen species (ROS) in the heart and YSM tissues, which could be partially rescued through the addition of antioxidants. In total, our study suggests that excess generation of ROS might play an important role in high-salt-induced defects in heart and angiogenesis.

Loss of insulin-induced activation of TRPM6 magnesium channels results in impaired glucose tolerance during pregnancy.

Hypomagnesemia affects insulin resistance and is a risk factor for diabetes mellitus type 2 (DM2) and gestational diabetes mellitus (GDM). Two single nucleotide polymorphisms (SNPs) in the epithelial magnesium channel TRPM6 (V(1393)I, K(1584)E) were predicted to confer susceptibility for DM2. Here, we show using patch clamp analysis and total internal reflection fluorescence microscopy, that insulin stimulates TRPM6 activity via a phosphoinositide 3-kinase and Rac1-mediated elevation of cell surface expression of TRPM6. Interestingly, insulin failed to activate the genetic variants TRPM6(V(1393)I) and TRPM6(K(1584)E), which is likely due to the inability of the insulin signaling pathway to phosphorylate TRPM6(T(1391)) and TRPM6(S(1583)). Moreover, by measuring total glycosylated hemoglobin (TGH) in 997 pregnant women as a measure of glucose control, we demonstrate that TRPM6(V(1393)I) and TRPM6(K(1584)E) are associated with higher TGH and confer a higher likelihood of developing GDM. The impaired response of TRPM6(V(1393)I) and TRPM6(K(1584)E) to insulin represents a unique molecular pathway leading to GDM where the defect is located in TRPM6.

Investigation into cyclic utilization of carbon source in an advanced sludge reduction, inorganic solids separation, phosphorus recovery, and enhanced nutrient removal (SIPER) wastewater treatment process.

An advanced wastewater treatment process (SIPER) was developed to simultaneously reduce sludge production, prevent the accumulation of inorganic solids, recover phosphorus, and enhance nutrient removal. The ability to recover organic substance from excess sludge to enhance nutrient removal (especially nitrogen) and its performance as a C-source were evaluated in this study. The chemical oxygen demand/total nitrogen (COD/TN) and volatile fatty acids/total phosphorus (VFA/TP) ratios for the supernatant of the alkaline-treated sludge were 3.1 times and 2.7 times those of the influent, respectively. The biodegradability of the supernatant was much better than that of the influent. The system COD was increased by 91 mg/L, and nitrogen removal was improved by 19.6% (the removal rate for TN reached 80.4%) after the return of the alkaline-treated sludge as an internal C-source. The C-source recovered from the excess sludge was successfully used to enhance nitrogen removal. The internal C-source contributed 24.1% of the total C-source, and the cyclic utilization of the system C-source was achieved by recirculation of alkaline-treated sludge in the sludge reduction, inorganic solids separation, phosphorus recovery (SIPER) process.