Biological Treatment Stage Research Articles

Analysis of dissolved organic matter characteristics in pharmaceutical wastewater via spectroscopy combined with Fourier-transform ion cyclotron resonance mass spectrometry

Studying the changes in organic matter and characteristic pollutants during the treatment of penicillin-containing pharmaceutical wastewater, which can be reflected by changes in dissolved organic matter (DOM), is crucial for improving the effectiveness of wastewater treatment units and systems. Herein, water quality indicators, spectroscopic methods, and Fourier-transform ion cyclotron resonance mass spectrometry were utilized to characterize the general molecular compositions and specific molecular changes in DOM during the treatment of typical penicillin-containing pharmaceutical wastewater, including in each of the influent, physicochemical treatment, biological treatment, oxidation treatment, and effluent stages. The influent exhibited a high organic matter content (concentration of dissolved organic carbon >10,000 mg·L−1), its DOM mainly contained protein- and lignin-like substances composed of CHON and CHONS molecules, and the relative intensity (RI) of penicillin was extremely high (RI = 0.220). Compared with the influent, the abundance of CHON and CHONS molecules detected after physicochemical treatment decreased by 70.3 % and 62.5 %, respectively, and the RI of penicillin decreased by 85.5 %. Biological treatment caused substantial changes in DOM components through oxidation, dealkylation, and denitrification reactions, accounting for 36.8 %, 28.9 %, and 14.8 % of the total identified reactions, respectively. Additionally, lignin-like substances were generated in large quantities, the overall humification level significantly increased, and the RI value increased for the penicillin intermediate, 6-aminopenicillanic acid (6-APA). Oxidation treatment effectively removed phosphorus-containing substances and some lignin-like substances produced by biological treatment; however, it was not effective in removing characteristic pollutants such as 6-APA. Such characteristic substances continued to be present in the effluent, and the DOM mainly contained protein- and humus-like substances, accounting for 30.8 % and 47.3 %, respectively. The study findings reveal the changes in organic matter and characteristic pollutants during the treatment of penicillin-containing wastewater from the perspective of the general molecular composition and specific molecular changes in DOM, providing support for further exploration of wastewater treatment mechanisms and improvements in treatment unit efficiency.

Occurrence, Fate, and Removal of Selected Antibiotics in Advanced Biological Urban Wastewater Treatment Plant

Wastewater treatment plants (WWTPs) are considered as one of the most important point sources for releasing antibiotics into the natural environment. In this study, the occurrence, fate, and removal of three antibiotics, ciprofloxacin (CIP), sulfamethoxazole (SMX), and azithromycin (AZI), belong to quinolone, sulfonamide, and macrolide groups, respectively were investigated seasonally in a large-scale urban WWTP. While the occurrence concentrations of the investigated antibiotics in raw wastewater were found between about 0.26 and 0.73 μg/L in the summer season, it was determined in the range of approximately 0.41 and 4.6 μg/L in the winter season. Although the removal efficiencies obtained for antibiotics in the pre-treatment stage of the studied advanced biological WWTP were not very high, the most treated compound in the pre-treatment stage was determined as CIP (up to 23.8%). Total removal efficiencies of the investigated antibiotics in the WWTP varied mainly based on the biological treatment stage of the WWTP. At the same time, removal efficiencies of the antibiotics obtained in the biological treatment also changed considerably depending on the seasons. Among all the investigated antibiotic compounds, it was determined that AZI was the compound that was least affected by the seasons in terms of the total removal efficiency obtained in WWTP. According to the annual average total removal efficiencies, it was determined that SMX (25.7%), CIP (71.3%), and AZI (89.2%) were treated poorly, moderately, and highly in WWTP, respectively. However, advanced biological WWTP was determined to be insufficient for the complete removal of total antibiotics.

Microbiological treatment of post-industrial water: Example of efficient bioremediation of the heavily polluted Kalina pond, Poland

The Kalina pond has been well known as a severely degraded area in the Silesia region, Poland. The environmental deterioration results from high contamination of water and bottom sediments with recalcitrant and toxic organic compounds, mainly phenol. The study was aimed at developing a bioremediation-based approach suitable for this type of polluted areas, involving microbiological treatment of water as a key and integral part of other necessary actions: mechanical interventions and the use of physical methods. During the initial biological treatment stage, autochthonous microorganisms were isolated from contaminated samples of water, soil and sediment, then subjected to strong selective pressure by incubation with the pollutants, and finally, cultivated to form a specialised microbial consortium consisting of five extremophilic bacterial strains. Consortium propagation and its biodegradation activity were optimised under variant conditions enabling bacteria to proliferate and to obtain high biomass density at large volumes allowing for the in situ application. After installing aeration systems in the pond, the consortium was surface-sprinkled to launch bioremediation and then both bacterial frequency and the contaminant level was systematically monitored. The complex remediation strategy proved efficient and was implemented on an industrial scale enabling successful remedial of the affected site. Treatment with the specifically targeted and adapted microbial consortium allowed for removal of most organic pollutants within a four-month season of 2022: the chemical oxygen demand (COD) value decreased by 72%, polyaromatic hydrocarbon (PAH) level by 97%, while the content of total phenols and other monoaromatic hydrocarbons (BTEX) dropped below the detection thresholds.

Sewage treatment in cities of the state of Minas Gerais, Brazil, that use the UASB reactor as the only biological treatment: A case study

This article analyzed the performance of four Wastewater Treatment Plants (WWTP) in three cities in the state of Minas Gerais, Brazil, which use the UASB (Upflow Anaerobic Sludge Blanket) reactor as the only stage of biological treatment. When evaluating the characteristics of treated wastewater, it was verified that the WWTPs were not efficient enough to meet the disposal standards established by environmental agencies. Most of the sewage samples from Ipatinga municipality did not meet the minimum removal for BOD5 of 60 % and COD of 55 %, being 56 % and 46 % the average removals, respectively. These results suggest the need for improvements in the current biological treatment and/or the adoption of a polishing step. The raw sewage had high biodegradability (BOD5/COD>0.4) and the UASB reactors reduced this biodegradability (ranging from 0.2 to 0.43) by removing the content of easier degradation. A strong linear correlation (R2 = 0.85) was observed between COD and DBO5 data for the raw sewage from Timóteo municipality, making it possible to estimate the second parameter as a function of the first. When compared with wastewater characterized and used in fertigation studies, the treated sewage samples of the present study show potential for application in agricultural practices.

Carbon accounting of A2O process based on carbon footprint in a full-scale municipal wastewater treatment plant

The traditional carbon accounting model for wastewater treatment plants (WWTPs) only calculates the total amount of each greenhouse gas (GHG), which has no guiding significance for the net zero carbon transformation of WWTPs under the goal of carbon neutrality, and the system boundary is only within the WWTPs. In this paper, the accounting boundary is extended to the outside of the plant, and the CO2 produced by the pumping pump outside the plant and the sludge transport is included in the accounting, which improves the accuracy of the results. In addition, the WWTP is divided into three stages, which are the pretreatment stage, biological treatment stage, and sludge treatment stage. The emission sources in each stage are calculated in detail to determine the key emission reduction targets in each stage. The research shows that the main carbon emission source in the pretreatment stage is indirect CO2 produced by chemicals, the main carbon emission source in the biological treatment stage is N2O emission, and the main carbon emission source in the sludge treatment stage is indirect CO2 produced by electricity consumption. We also found that the carbon intensity of the biological treatment stage was 1.8 times that of the other two stages. Therefore, carbon emission reduction in the biological stage is the focus of plant emission reduction.

Fluorimetric microplate assay for the determination of extracellular alkaline phosphatase kinetics and inhibition kinetics in activated sludge

The microbial enzyme alkaline phosphatase contributes to the removal of organic phosphorus compounds from wastewaters. To cope with regulatory threshold values for permitted maximum phosphor concentrations in treated wastewaters, a high activity of this enzyme in the biological treatment stage, e.g., the activated sludge process, is required. To investigate the reaction dynamics of this enzyme, to analyze substrate selectivities, and to identify potential inhibitors, the determination of enzyme kinetics is necessary. A method based on the application of the synthetic fluorogenic substrate 4-methylumbelliferyl phosphate is proven for soils, but not for activated sludges. Here, we adapt this procedure to the latter. The adapted method offers the additional benefit to determine inhibition kinetics. In contrast to conventional photometric assays, no particle removal, e.g., of sludge pellets, is required enabling the analysis of the whole sludge suspension as well as of specific sludge fractions. The high sensitivity of fluorescence detection allows the selection of a wide substrate concentration range for sound modeling of kinetic functions.•Fluorescence array technique for fast and sensitive analysis of high sample numbers•No need for particle separation – analysis of the whole (diluted) sludge suspension•Simultaneous determination of standard and inhibition kinetics

Fate of emerging contaminants in a sequencing batch reactor and potential of biological activated carbon as tertiary treatment for the removal of persisting contaminants

The study aims to understand the occurrence and removal of 20 emerging contaminants (ECs) in each unit process of a sequencing batch reactor-based wastewater treatment plant (WWTP) and explore the potential of biological activated carbon (BAC) for the treatment of residual ECs and organic matter in the secondary effluent. Analgesic-acetaminophen, anti-inflammatory drug-ibuprofen, and stimulant-caffeine were detected at high concentrations in the influent. Most of the removal was observed in the biological treatment stage in the SBR basins. The mass load of the ECs was 2.93 g/d in the secondary effluent and 0.4 g/d in the final sludge, while the total removal of the mass load of ECs till the secondary treatment stage was 93.22%. 12 of the 20 ECs were removed by more than 50%, while carbamazepine (negative removal), sulfamethoxazole, and trimethoprim were removed by less than 20%. As a polishing step and to remove residual ECs, two BAC units were studied for 11,000 bed volumes (324 days). Packed column studies on granular activated carbon were conducted, and GAC development to BAC was monitored. SEM and FTIR were used to confirm and characterize the BAC. The BAC appeared to be more hydrophobic than the GAC. The BAC removed 78.4% and 40% of the dissolved ECs and organic carbon at an optimum EBCT of 25 min. Carbamazepine, sulfamethoxazole, and trimethoprim were removed by 61.5, 84, and 52.2%, respectively. Parallel column tests revealed adsorption as an important mechanism for the removal of positively charged compounds. The results indicate that the BAC is an effective tertiary/polishing technique for removing organic and micropollutants in the secondary wastewater effluent.

Improvement of the Treatment Performance of the Conventional Wastewater Treatment Plant: A Case Study of the Central Wastewater Treatment Plant in Ulaanbaatar, Mongolia

This study is carried out within the framework of the requirements of ensuring reliable operation of the Central Wastewater Treatment Plant of Ulaanbaatar to increase the treatment performance and mitigate the adverse impacts of the current poor performance on nature and ecology. The dynamic of the current influent was studied in order to find the best-suited solution as a means of improvement for the WWTP. As an immediate and fast-to-build solution, an equalization tank and pre-aeration facilities were proposed. The positive effect of the facilities on the biological treatment stage and the overall treatment performance was estimated both theoretically and empirically. The results showed that the overall performance of the treatment for BOD5 and TSS will be increased by up to 30% and 10%, respectively. Furthermore, the high fluctuation problems the central WWTP in terms of hydraulic and pollution load will be positively affected by the intervention, eliminating the main cause of the current poor treatment performance.

Influence of the nitrification stage of biological treatment to the levels of nitrogen compounds in wastewater treatment

Influence of the nitrification stage of biological treatment to the levels of nitrogen compounds in wastewater treatment

Key points of breast cancer management under public health emergencies.

Since the end of February 2022, China has experienced a new wave of coronavirus disease 2019 (COVID-19) outbreaks caused by the Omicron variant. These outbreaks frequently occur at multiple sites, involving many provinces and cities. Prevention and control work is facing more challenges only after the Wuhan epidemic. As a general principle, the priority of treatment should be determined according to the biological features, clinical stages, and treatment stages of different breast cancer (BC) subtypes, and individualized diagnosis and treatment recommendations should be given. These patients belong to a high-priority population, for whom receiving treatment in a hospital is urgently required. In addition, treatment should also be prioritized for patients experiencing new tumor-related symptoms or serious adverse events. If the disease condition is stable, the frequency of follow-up re-examinations can be reduced according to the epidemic control situation. Online diagnosis and treatment are recommended to maintain doctor-patient communication. However, special attention should still be paid to treatment-associated safety issues, and safety monitoring measures should be adopted. For low-priority patients with stable disease, elective follow-up visits may be arranged after risk-benefit assessment based on the severity of the local COVID-19 epidemic and the risk of infection. Based on the above principle, we once again present our opinions on the top ten hot issues concerning the clinical diagnosis and treatment of BC during the COVID-19 epidemic in China.

Tertiary Treatment of Secondary Effluents from the East WWTP of Tizi-Ouzou (Algeria) with the Aqueous Extract of Ceratonia Siliqua Green Pod

The antibacterial action of the carob tree offers the possibility of using it for the disinfection of treated wastewater in biological process wastewater treatment plants. This paper reviews studies conducted to investigate the effect of carob tree on the reduction of indicator bacteria of fecal contamination that cannot be removed after the secondary stage of biological treatment. The aim is to use the wastewater safely in irrigation and expand the list of irrigable plants with this unexploited resource. Physico-chemical and bacteriological parameters were used to determine the optimal conditions and evaluate the treatment’s efficiency. A contact time of 1 h and a dose of 1 mL of disinfectant reduced E. coli and fecal coliforms from 5.105 CFU to 1 237 CFU (99.75%) and from 7.106 CFU to 1 505 CFU (99.98%), respectively. For the same contact time, the fecal streptococci were reduced from 4.105 CFU to 59 CFU (99.99%). According to WHO standards, this dose and contact time are sufficient to use this water for irrigation. A minimum contact time of 2 h with a dose of 1 mL of the aqueous extract of the green pod of the carob is required to obtain a reduction of E. coli and fecal coliforms from 5.105 CFU to 5 254 CFU (99.95%) and from 7.106 CFU to 340 CFU (99. 99%) to meet the Algerian standards of reuse of treated wastewater being more stringent. The results show that the same conditions reduce fecal streptococci from 4.105 CFU to 5 CFU (99.99%). This elimination level shows that green carob juice can be used for disinfection with the necessary doses for each bacterial load and sufficient contact time.

Wastewater substrate disinfection for cyanobacteria cultivation as tertiary treatment.

Cultivation of microalgae or/and cyanobacteria in nutrient-rich wastewaters offers an opportunity for enhancing sustainability of tertiary wastewater treatment processes via resources/energy recovery/production, mitigation of emitted GHGs and provision of added value products. However, maintaining a monoculture in wastewater-media constitutes a significant challenge to be addressed. In this regard, the present work assesses the efficiency of the low-cost wastewater substrate disinfection techniques of filtration, use of NaClO, H2O2 or Fe(VI), as a preliminary treatment stage upstream a cyanobacteria cultivation photobioreactor. The growth rate of cyanobacterium Synechococcus elongatus PCC 7942, and nitrate and phosphate removal rates, were experimentally assessed in cultivation setups with biologically treated dairy wastewater that had been subjected to a single or a synergetic couple of disinfection techniques. The results showed that filter thickness has a greater effect on disinfection efficiency than filter pore size. Furthermore, the disinfection efficiency of Fe(VI), which was produced on-site by electrosynthesis via a Fe0/Fe0 cell, was greater than that of NaClO and H2O2. Filtration at ≤ 1.2-μm pore size coupled with chemical disinfection led to unhindered Synechococcus elongatus PCC 7942 growth and efficient nitrate and phosphate removal rates, at dosages, in terms of Concentreation-Time (CT) product,of CT ≥ 270mgmin L-1 for NaClO and CT ≥ 157mgmin L-1 for Fe(VI). The coagulation action of Fe(III) species that result from Fe(VI) reduction and the oxidation action of Fe(VI) can assist in turbidity, organic compounds and phosphorous removal from wastewater media. Moreover, the residual iron species can assist in Synechococcus elongatus PCC 7942 harvesting and may enhance photosynthesis rate by increasing light transfer efficiency. Thus, a filtration configuration coupled with chemical disinfection, preferably using ferrates, downstream of sedimentation tank of a secondary biological wastewater treatment stage is proposed as a necessary, efficient and low-cost disinfection technique for full-scale scale implementation of cyanobacteria cultivation as tertiary wastewater processes.

Combining Shift to Biogas Production in a Large WWTP in China with Optimisation of Nitrogen Removal

Despite the huge current challenges in sewage sludge treatment and disposal in China, anaerobic sludge stabilisation (AnSS) is still not a state-of-the-art process in WWTP in the country. However, the potential benefits of anaerobic sludge stabilisation may outweigh the drawbacks. One of these drawbacks is the backload from the sludge liquor that increases the nutrient load in the biological treatment stage. This work shows via computer modelling that not only can the sludge production and disposal costs be significantly reduced, but also that, with sensible automation and operational strategies (e.g., bypass of primary clarifiers, use of a centrate dosing strategy, incorporation of ammonium nitrogen sensors, etc.), the effects of the backload can be counteracted for nitrogen removal, even considering that wastewater in China often has an unfavourable C/N ratio for nitrogen removal. The tested strategies would even improve the overall plant performance in terms of norm compliance, sludge production, energy use, and energy production

Local Wastewater Treatment Plant for Dairy Production: Challenges and Solutions

Main factors that can negatively affect the operation of wastewater treatment plant for dairy production were identified. The main negative factors are: low automation of the process, high concentrations of chemical reagents that have a detrimental effect on the biological treatment stage, temporary fluctuations in pH values, insufficient amount of dissolved oxygen at the biological treatment stage. One of the main operation problems of local dairy wastewater treatment plant is a fluctuation of pH value over a wide range, especially at treatment plants of small enterprises. Biological treatment methods were considered as one of the most suitable technologies for the removal of organic substances from dairy wastewater. It was concluded that there are quite stringent conditions for each treatment stage. The pH range is almost neutral and fluctuate within 6-8.5. The average temperature of wastewater should be 20-30°C for optimal biochemical reactions. The concentration of dissolved oxygen plays an overriding concern for biological treatment stage, since good operation of processes of nitrification, denitrification and biological phosphorus removal are based on this indicator and will not proceed in case of deviations from the normal.

Improving the photobioreactor operation efficiency in the technological scheme of wastewater treatment

Conventional process schemes of municipal sewage water treatment, advantages, and disadvantages of the methods applied when removing biogenic elements were considered. It was shown that the existing shortcomings cause additional explicit costs and difficulties when disposing of the resulting waste. Low efficiency of the removal processes themselves causing residual concentrations of biogenic elements in the treated sewage water was also shown. A process scheme for treating municipal sewage water was proposed. It includes the use of a photobioreactor of a proposed design for the removal of biogenic elements due to the metabolism of microalgae. It was experimentally shown that the use of Euglena gracilis strain for removal of phosphates in initial concentrations of 4, 7, and 14 mg/dm3 from sewage water is the most efficient way. It makes it possible to reduce these concentrations to residual 0…0.55 mg/dm3 in four days. A 3.75…5.58 times increment of microalgae biomass during this period was also shown. A mathematical model was constructed for calculating the time of staying the sewage water and microalgae mixture in a photobioreactor to achieve the required degree of removal of biogenic elements. Based on the proposed model and experimental studies, the required time of staying in the rector working area was calculated. It was shown that with the use of Euglena gracilis strain but without removal of biogenic elements at previous purification stages (process schemes including only mechanical purification), the time of mixture staying in the working zone was 37.81 hrs. With partial removal of biogenic elements at the stage of biological treatment (0.55 mg/dm3 total nitrogen, 0.91 mg/dm3 ammonium nitrogen, 0.44 mg/dm3 phosphates), this time was reduced to 26.66 hrs. It was found that the use of Euglena gracilis strain instead of Chlorella vulgaris (FC-16) in the removal of phosphates results in a 2-time increase in the process efficiency and a 50 % decrease in time of mixture staying in the working zone. Recommendations for calculating geometric parameters of photobioreactors of the proposed design were given for use in the process schemes

A Software Emulator for the Modelling and Control of an Activated Sludge Process in a Wastewater Treatment Plant

The design and implementation of a simulator, as a real-time application, for a complex process from the biological treatment stage of a wastewater treatment plant (WWTP), is addressed. More precisely, this emulator was achieved as a software tool that can be later integrated into a more complex SCADA (supervisory control and data acquisition) system of the WWTP Făcăi, Romania. The basic idea is to implement and validate a reduced-order model of the activated sludge process (ASP), initially simulated in the Matlab/Simulink environment (The MathWorks, Inc., Natick, MA, USA). Moreover, an advanced multivariable adaptive control scheme of the ASP is addressed. This software tool can be made to work in parallel with the evolution of the process and can have as input signals measured directly at the process level, possibly following parametric or model adaptations. The software emulator is developed in the LabWindows/CVI programming environment (National Instruments), which offers low-level access to hardware or software systems that have minimal open-architecture facilities. This environment provides versatile drivers and software packages that can facilitate the interaction with software tools developed within some earlier SCADA systems. The structure and the graphical interface of the emulator, some functionalities, experiments, and evolution of main variables are presented.

The efficiency of some fungi species in wastewater treatment

Using microorganisms in eliminating or reducing the impacts of harmful remnants is very ancient manner. The current study was conducted to explore the potential of utilizing some fungi species that isolated from the main sewage treatment plant in Al-Muamirah area, Babylon-Iraq, in reducing some pollutants. Six fungi taxa Aspergillus flavus, A. niger, A. terrues, Candida albicans, C. krusei, and Penicillium digitatum were identified before any treatment process, whereas only four fungi species A. flavus 20%, A. niger 20%, A. terrues 10%, and P. digitatum 18% were recognized after completing the physical and chemical treatment stages. Only three taxa A. niger, A. terrues, and P. digitatum were employed to reveal their capability in treating the sewage water, which represent the biological treatment stage as the final step of the treatment processes. The results showed a considerable capability of these fungi species in decreasing many variables values such as pH, total soluble solids (TSS), electrical conductivity (EC), salinity, total alkalinity, chlorides, nitrite, and phosphate. Where, slightly low reduction was detected in TSS value in all experiments (1.1–5.9%), similarly, both EC and salinity which were decreased with low ratios (6.6%, 3.9%, respectively). Taxon A. terrues exhibited high ability in reducing the total alkalinity and chloride ions in the treated water (30.9%, 43%, respectively) in comparison with the other two fungi species. Furthermore, all three fungi species were posed high capability in decreasing nutrients, where both nitrite and phosphate ions were highly reduced (87–97% and 22.8–32.1%, respectively). Based on these findings, we suggest using other microorganisms and exploring their capacity in removing the pollutants, and revealing the ability of the above fungi taxa in removing other pollutants.

Impact of Hospital Wastewater on the Occurrence and Diversity of Beta-Lactamase Genes During Wastewater Treatment with an Emphasis on Carbapenemase Genes: A Metagenomic Approach

The diversity of beta-lactam antibiotic resistance genes, with particular emphasis on carbapenemase genes, during the treatment process at two wastewater treatment plants (WWTPs) with different levels of hospital wastewater inflow was investigated using high-throughput sequencing. An additional aspect of the study was to determine the taxonomic diversity of microorganisms in the studied samples. The obtained results suggest that bacteria of the Fusobacteriaceae family, not associated to date with this phenomenon, may be involved in the spread of antibiotic resistance in the environment. In samples from both wastewater treatment plants, the dominant beta-lactamase genes included blaOXA, blaGES, blaBEL, blaCfxA, and blaTEM. It is worth noting that the blaKPC and blaNDM genes were only found in untreated municipal wastewater with a higher hospital wastewater content. Moreover, an increase in the abundance of the blaIMP gene after the biological treatment stage in the studied treatment plants was found. In wastewater characterized by a higher proportion of hospital wastewater, 94 correlations were observed, while in wastewater with its lower proportion, 41 correlations were noted. Considering the above, the current research indicates that the inflow of hospital wastewater contributes to the spread of antibiotic resistance in the aquatic environment.

PROSPECTS FOR BIOLOGICAL TREATMENT OF OLEAGINOUS CROP PROCESSING WASTE WATER

The possibility of microbial treatment of waste waters of an enterprise for deep prcessing of oilseeds has been studied. It was found that the most effective cleaning occurs when using a consortium that includes strains Rhodococcus ruber 1NG, Bacillus
 sp. FL X-5, Azotobacter sp. FL9-MV and Rhodococcus wratislaviensis G-13. The efficiency of purification of oily wastewater with an initial COD of 4425 mg O2/dm3 on the 5th day was 37.7 %, on the 21st day – 40 %. High results of purification of the investigated effluents were also achieved with the use of microbial preparations of the Antoil series. The cleaning efficiency on the 21st day was 33.7–37 %.
 The results obtained indicate that the use of specialized microorganisms-destructors at the stage of biological wastewater treatment of enterprises for deep processing of oilseeds is promising.

Phosphorus recycling from activated sludge of full-scale wastewater treatment plants by fast inversion of the biological phosphorus elimination mechanism

Enhanced biological phosphorus removal (EBPR) is often applied by wastewater treatment plants (WWTPs) whereby phosphorus (P) is accumulated in the activated sludge (AS) biomass. The German Sewage Sludge Ordinance demands that large WWTPs recycle P from their process streams by 2029. This study aimed at evaluating the potential of an acetate-mediated P re-dissolution from non-acclimated AS of three full-scale WWTPs. All AS exhibited enhanced P re-dissolution during acetate uptake and followed kinetics typical of EBPR systems. Re-dissolution efficiency differed depending on the WWTP operation mode. The highest P re-dissolution yield (56% of total P) was obtained for pure EBPR sludge. Lower re-dissolution rates of 19–22% were observed in the AS from WWTPs that employed additional chemical P removal, probably due to shortage of intracellular polyphosphate. Pure EBPR systems may be suited for the implementation of a re-dissolution based strategy for P recycling from AS where P depleted AS could potentially be returned to the biological treatment stage.