The characteristics of the bacterial community structure and population dynamics for phosphorus removal in SBR activated sludge processes

Enhanced Bio-P removal: Past, present, and future - A comprehensive review

Excess amounts of phosphorus (P) and nitrogen (N) from anthropogenic activities such as population growth, municipal and industrial wastewater discharges, agriculture fertilization and storm water runoffs, have affected surface water chemistry, resulting in episodes of eutrophication. Enhanced biological phosphorus removal (EBPR) based treatment processes are an economical and environmentally friendly solution to address the present environmental impacts caused by excess P present in municipal discharges. EBPR practices have been researched and operated for more than five decades worldwide, with promising results in decreasing orthophosphate to acceptable levels. The advent of molecular tools targeting bacterial genomic deoxyribonucleic acid (DNA) has also helped us reveal the identity of potential polyphosphate-accumulating organisms (PAO) and denitrifying PAO (DPAO) responsible for the success of EBPR. Integration of process engineering and environmental microbiology has provided much-needed confidence to the wastewater community for the successful implementation of EBPR practices around the globe. Despite these successes, the process of EBPR continues to evolve in terms of its microbiology and application in light of other biological processes such as anaerobic ammonia oxidation and on-site carbon capture. This review provides an overview of the history of EBPR, discusses different operational parameters critical for the successful operation of EBPR systems, reviews current knowledge of EBPR microbiology, the influence of PAO/DPAO on the disintegration of microbial communities, stoichiometry, EBPR clades, current practices, and upcoming potential innovations.

Interaction between β-lactam antibiotic and phosphorus-accumulating organisms

β-Lactam antibiotics have been widely used in clinic due to strong antibacterial activity with mild adverse side effects and have been detected in the environment. In the enhanced biological phosphorus removal (EBPR) process, phosphorus-accumulating organisms (PAOs) play a major role. In this study, amoxicillin, aztreonam, and cefoperazone are the selected antibiotics that applied in investigating the interaction mechanism of β-lactam antibiotics and PAO. The effects of β-lactam antibiotics on PAOs were analyzed comprehensively from the aspects of antibiotic impacts on phosphorus removal rate, intracellular polymer, their toxicity to PAOs, and PAO impacts on the fate of β-lactam antibiotics. It was found that the phosphorus removal rate of PAO increased by 19.21% and 15.75%, respectively at 10 mg/L amoxicillin and aztreonam, while cefoperazone had certain inhibition effect on phosphorus removal efficiency. Quantitative analysis shows that in the aerobic stage, three kinds of β-lactam antibiotics could promote the synthesis of polyphosphates (poly-P). The degradation rates of three antibiotics were as follows: amoxicillin > aztreonam > cefoperazone. The fate characteristics of antibiotics provide a theoretical basis for environmental risk assessment. The toxic effects of three antibiotics were as follows: cefoperazone > aztreonam > amoxicillin according to the bacteriostatic test. It provided a scientific theoretical basis for systematically evaluating the biological toxicity of antibiotic pollutants.

Nutrient removal and microbial community in a two-stage process: Simultaneous enhanced biological phosphorus removal and semi-nitritation (EBPR-SN) followed by anammox

This study developed a two-stage process, including simultaneous enhanced biological phosphorus-removal and semi-nitritation (EBPR-SN) sequencing batch reactor (SBR), followed by Anammox SBR, to achieve advanced nitrogen (N) and phosphorus (P) removal from real sewage with low carbon/nitrogen (2.82). The long-term operation suggested that removal efficiencies for TIN (86.2 ± 3.5%) and P (95.0 ± 5.5%) were stably obtained, with nitrite accumulation ratio of 98.7% in EBPR-SN SBR. Mechanism analysis indicated contribution of anammox to N-removal being 57.3%-73.7% and superior P-removal due to the majority of removed organics (~74.5%) being stored by polyphosphate-accumulating organisms (PAOs). In EBPR-SN SBR, high-throughput sequencing showed ammonium-oxidizing bacteria was 0.03% while nitrite-oxidizing bacteria was not detected, and PAOs accounted for 30.07%. In Anammox SBR, Candidatus Brocadia (9.75%) was the only anammox bacteria. Remarkably, short aerobic hydraulic retention time (4.29 h) with low DO (0.3-1.2 mg/L) during the whole process provided desirable energy-saving.

Field assessment of bacterial communities and total trihalomethanes: Implications for drinking water networks

Operation and maintenance (O&M) of drinking water distribution networks (DWDNs) in tropical countries simultaneously face the control of acute and chronic risks due to the presence of microorganisms and disinfection by-products, respectively. In this study, results from a detailed field characterization of microbiological, chemical and infrastructural parameters of a tropical-climate DWDN are presented. Water physicochemical parameters and the characteristics of the network were assessed to evaluate the relationship between abiotic and microbiological factors and their association with the presence of total trihalomethanes (TTHMs). Illumina sequencing of the bacterial 16s rRNA gene revealed significant differences in the composition of biofilm and planktonic communities. The highly diverse biofilm communities showed the presence of methylotrophic bacteria, which suggest the presence of methyl radicals such as THMs within this habitat. Microbiological parameters correlated with water age, pH, temperature and free residual chlorine. The results from this study are necessary to increase the awareness of O&M practices in DWDNs required to reduce biofilm formation and maintain appropriate microbiological and chemical water quality, in relation to biofilm detachment and DBP formation.

Phosphorus (P) recovery coupled with increasing influent ammonium facilitated intracellular carbon source storage and simultaneous aerobic phosphorus & nitrogen removal

Under decreasing C/N (from 8.8 to 3.5) conditions, an alternating anaerobic/aerobic biofilter (AABF) was used to remove nitrogen and accumulate/recover phosphorus (P) from synthetic wastewater. The AABF was periodically (every 10 days) fed with an additional carbon source (10 L, chemical oxygen demand (COD) = 900 mg L^-1 sodium acetate (NaAC) solution) in the anaerobic phase to induce the release of P sequestered in the biofilm. An increase in PHA storage in the biofilm was observed and characterized with TEM and a GC-MS method. The accumulation of P and removal of total nitrogen occurred primarily in the aerobic phase. As the NH₄⁺-N loading rate increased from 0.095 to 0.238 kg m^-3 d^-1 at a total empty bed retention time (EBRT) of 4.6 h, the TN removal in AABF was reduced from 91.2% to 43.4%, while the P removal or recovery rate remained unaffected. The high-throughput community sequencing analysis indicated that the relative abundance of Candidatus Competibacter, Nitrospira and Arcobacter increased while the Accumulibacter phosphatis decreased with an increase of ammonium loading rate within a short operational period (30 days). A putative N and P removal pattern via simultaneous nitrification and PHA-based denitrification, as well as P accumulation in the biofilm was proposed. The research demonstrated that an efficient N removal and P recovery process, i.e., simultaneous nitrification and denitrification, P accumulation and carbon source-regulated P recovery can be achieved by the symbiotic functional groups in a single biofilm reactor.

Enhanced phosphorus recovery and biofilm microbial community changes in an alternating anaerobic/aerobic biofilter

The operation of an alternating anaerobic/aerobic biofilter (AABF), treating synthetic wastewater, was modified to enhance recovery of phosphorus (P). The AABF was periodically fed with an additional carbon source during the anaerobic phase to force the release of biofilm-sequestered P which was then harvested and recovered. A maximum of 48% of the total influent P was found to be released in the solution for recovery. Upon implementation of periodic P bio-sequestering and P harvesting, the predominant bacterial communities changed from β-Proteobacteria to γ-Proteobacteria groups. The genus Pseudomonas of γ-Proteobacteria was found to enrich greatly with 98% dominance. Dense intracellular poly-P granules were found within the cells of the biofilm, confirming the presence of P accumulating organisms (PAOs). Periodic addition of a carbon source to the AABF coupled with intracellular P reduction during the anaerobic phase most probably exerted environmental stress in the selection of Pseudomonas PAOs over PAOs of other phylogenic types. Results of the study provided operational information on the selection of certain microbial communities for P removal and recovery. This information can be used to further advance P recovery in biofilm systems such as the AABFs.

Effect of different carbon sources on the biological phosphorus removal by a sequencing batch reactor using pressurized pure oxygen

The effect of different carbon source on the efficiency of enhanced biological phosphorus removal (EBPR) from synthetic wastewater with acetate and two ratios of acetate/starch as a carbon source was investigated. Three pressurized pure oxygen sequencing batch reactor (POSBR) experiments were operated. The reactors (POSBR1, POSBR2 and POSBR3) were developed and studied at different carbon source ratios of 100% acetate, 75% acetate plus 25% starch and 50% acetate plus 50% starch, respectively. The results showed that POSBR1 had a higher phosphate release-to-uptake ratio and, respectively, in a much higher phosphorus removal efficiency (93.8%) than POSBR2 (84.7%) and POSBR3 (77.3%) within 30 days of operation. This indicated that the phosphorus removal efficiency decreased the higher the starch concentration was. It was also found that POSBR1 produced more polyhydroxyalkanoates (PHAs) than the other reactors. Based on the effect of the carbon source on the PHA concentration and consumption, the conditions of POSBR1 were favourable for the growth of polyphosphate-accumulating organisms and therefore, beneficial for the biological phosphorus removal process.

Effects of idle time on biological phosphorus removal by sequencing batch reactors

Three identical sequencing batch reactors (SBRs) were operated to investigate the effects of various idle times on the biological phosphorus (P) removal. The idle times were set to 3 hr (R1), 10 hr (R2) and 17 hr (R3). The results showed that the idle time of a SBR had potential impact on biological phosphorus removal, especially when the influent phosphorus concentration increased. The phosphorus removal efficiencies of the R2 and R3 systems declined dramatically compared with the stable R1 system, and the P-release and P-uptake rates of the R3 system in particular decreased dramatically. The PCR-DGGE analysis showed that uncultured Pseudomonas sp. (GQ183242.1) and beta-Proteobacteria (AY823971) were the dominant phosphorus removal bacteria for the R1 and R2 systems, while uncultured gamma-Proteobacteria were the dominant phosphorus removal bacteria for the R3 system. Glycogen-accumulating organisms (GAOs), such as uncultured Sphingomonas sp. (AM889077), were found in the R2 and R3 systems. Overall, the R1 system was the most stable and exhibited the best phosphorus removal efficiency. It was found that although the idle time can be prolonged to allow the formation of intracellular polymers when the phosphorus concentration of the influent is low, systems with a long idle time can become unstable when the influent phosphorus concentration is increased.

Biodegradation of phytosanitary products in biological wastewater treatment

Agricultural activity generates two types of waste: firstly, biodegradable organic effluents generally treated by biological processes and, secondly, phytosanitary effluents which contain residues of plant protection products. The latter are collected and treated. Current technological solutions are essentially based on concentration or physical-chemical processes. However, recent improvements in the biodegradability of pesticides open the way to the consideration of alternative, biological, treatment using mixed liquor from wastewater plant activated sludge. The feasibility of the biological treatment of viticultural effluents has been evaluated by the application of pesticides to activated sludge. The necessity for selection of a pesticide-resistant biomass has been highlighted. The elimination of the phytosanitary products shows the potential of a resistant biomass in the treatment of pesticides. The aerated biological storage ponds at three wineries, followed by a sand or reed-bed filter, were used for the treatment of the total annual volume of the viticulture effluents and validate the laboratory experiments. The results show that the biological purification of pesticides by activated sludge is possible by allowing approximately 8 days for biomass adaptation. Stability of purification occurs between 20 and 30 days.

Biological phosphorus removal in sequencing batch reactor with single-stage oxic process

The performance of biological phosphorus removal (BPR) in a sequencing batch reactor (SBR) with single-stage oxic process was investigated using simulated municipal wastewater. The experimental results showed that BPR could be achieved in a SBR without anaerobic phase, which was conventionally considered as a key phase for BPR. Phosphorus (P) concentration 0.22-1.79 mg L(-1) in effluent can be obtained after 4h aeration when P concentration in influent was about 15-20 mg L(-1), the dissolved oxygen (DO) was controlled at 3+/-0.2 mg L(-1) during aerobic phase and pH was maintained 7+/-0.1, which indicated the efficiencies of P removal were achieved 90% above. Experimental results also showed that P was mainly stored in the form of intracellular storage of polyphosphate (poly-P), and about 207.235 mg phosphates have been removed by the discharge of rich-phosphorus sludge for each SBR cycle. However, the energy storage poly-beta-hydroxyalkanoates (PHA) was almost kept constant at a low level (5-6 mg L(-1)) during the process. Those results showed that phosphate could be transformed to poly-P with single-stage oxic process without PHA accumulation, and BPR could be realized in net phosphate removal.

Microbial community succession and lignocellulose degradation during agricultural waste composting

The changes of microbial community during agricultural waste composting were successfully studied by quinone profiles. Mesophilic bacteria indicated by MK-7 and mesophilic fungi containing Q-9 as major quinone were predominant and seemed to be important during the initial stage of composting. Actinobacteria indicated by a series of partially saturated and long-chain menaquinones were preponderant during the thermophilic period. While Actinobacteria, fungi and some bacteria, especially those microbes containing MK-7(H4) found in Gram-positive bacteria with a low G+C content or Actinobacteria were found cooperate during the latter maturating period. Since lignocellulose is abundant in the agricultural wastes and its degradation is essential for the operation of composting, it's important to establish the correlation between the quinone profiles changes and lignocellulose degradation. The microbes containing Q-9 or Q-10(H2) as major quinone were found to be the most important hemicellulose and cellulose degrading microorganisms during composting. While the microorganisms containing Q-9(H2) as major quinone and many thermophilic Actinobacteria were believed to be responsible for lignin degradation during agricultural waste composting.

Microbial population dynamics at effluent treatment plants

The requirements for treated wastewater are becoming increasingly more stringent, and therefore the improved efficiency of biological treatment processes is indispensable at industrial effluent treatment plants (ETPs). Microorganisms such as bacteria play an important role in the natural cycling of materials and particularly in the decomposition of organic wastes. The knowledge of the interactions among these microbial populations needs to be harnessed for optimum evaluation and functioning of effluent treatment plants. Modern molecular techniques have revolutionized the methods of assessing these microbial populations. The combination of the results of these microbial assessments along with the on-site parameters at ETPs would favor an efficient treatment. In this review, the various approaches and importance of correlating the microbial population dynamics and treatment of wastewater at industrial ETPs has been elaborated.