Novel three-sludge municipal wastewater treatment process coupling denitrifying phosphorus removal with anaerobic ammonium oxidation.

The two-sludge anoxic dephosphation (DEPHANOX) process frequently encounters the challenge of elevated effluent ammonia levels in practical applications. In this study, the anaerobic ammonium oxidation (anammox) biofilm was introduced into the DEPHANOX system, transforming it into a three-sludge system, enabling synchronous nitrogen and phosphorus elimination, particularly targeting ammonia. Despite a chemical oxygen demand/total nitrogen ratio of 4.3 ± 0.8 in the actual municipal wastewater and 4.5 h of aeration, the effluent total nitrogen was 13.7 mg/L, lower than the parallel wastewater treatment plant. Additionally, the effluent ammonia reduced to 5.1 ± 2.5 mg/L. Notably, denitrifying phosphorus removal and anammox were coupled in the anoxic zone, yielding 74.5 % nitrogen and 87.8 % phosphorus removal. 16S rRNA gene sequencing identified denitrifying phosphorus-accumulating organisms primarily in floc sludge (Saprospiraceae 7.07 %, Anaerolineaceae 1.95 %, Tetrasphaera 1.57 %), while anammox bacteria inhabited the biofilm (Candidatus Brocadia 4.00 %). This study presents a novel process for efficiently treating municipal wastewater.

Carbon neutrality in wastewater treatment plants: An integrated biotechnological-based solution for nutrients recovery, odour abatement and CO2 conversion in alternative energy drivers.

Wastewater treatment plants play a crucial role in water security and sanitation, ensuring ecosystems balance and avoiding significant negative effects on humans and environment. However, they determine also negative pressures, including greenhouse gas and odourous emissions, which should be minimized to mitigate climate changes besides avoiding complaints. The research has been focused on the validation of an innovative integrated biological system for the sustainable treatment of complex gaseous emissions from wastewater treatment plants. The proposed system consists of a moving bed biofilm reactor coupled with an algal photobioreactor, with the dual objective of: i) reducing the inlet concentration of the odourous contaminants (in this case, hydrogen sulphide, toluene and p-xylene); ii) capturing and converting the carbon dioxide emissions produced by the degradation process into exploitable algal biomass. The first reactor promoted the degradation of chemical compounds up to 99.57% for an inlet load (IL) of 22.97 g m-3 d-1 while the second allowed the capture of the CO2 resulting from the degradation of gaseous compounds, with biofixation rate up to 81.55%. The absorbed CO2 was converted in valuable feedstocks, with a maximum algal biomass productivity in aPBR of 0.22 g L-1 d-1. Dairy wastewater has been used as alternative nutrient source for both reactors, with a view of reusing wastewater while cultivating biomass, framing the proposed technology in a context of a biorefinery within a circular economy perspective. The biomass produced in the algal photobioreactor was indeed characterized by a high lipid content, with a maximum percentage of lipids per dry weight biomass of 35%. The biomass can therefore be exploited for the production of alternative and clean energy carrier. The proposed biotechnology represents an effective tool for shifiting the conventional plants in carbon neutral platform for implementing principles of ecological transition while achieving high levels of environmental protection.

Immobilized microalgae: principles, processes and its applications in wastewater treatment.

Microalgae have emerged as potential candidates for biomass production and pollutant removal. However, expensive biomass harvesting, insufficient biomass productivity, and low energy intensity limit the large-scale production of microalgae. To break through these bottlenecks, a novel technology of immobilized microalgae culture coupled with wastewater treatment has received increasing attention in recent years. In this review, the characteristics of two immobilized microalgae culture technologies are first presented and then their mechanisms are discussed in terms of biofilm formation theories, including thermodynamic theory, Derjaguin-Landau-Verwei-Overbeek theory (DLVO) and its extended theory (xDLVO), as well as ionic cross-linking mechanisms in the process of microalgae encapsulated in alginate. The main factors (algal strains, carriers, and culture conditions) affecting the growth of microalgae are also discussed. It is also summarized that immobilized microalgae show considerable potential for nitrogen and phosphorus removal, heavy metal removal, pesticide and antibiotic removal in wastewater treatment. The role of bacteria in the cultivation of microalgae by immobilization techniques and their application in wastewater treatment are clarified. This is economically feasible and technically superior. The problems and challenges faced by immobilized microalgae are finally presented.

Manganese dioxide decorated kiwi peel powder for efficient removal of lead from aqueous solutions, blood and Traditional Chinese Medicine extracts.

For human health and environment safety, it is of great significance to develop novel materials with high effectiveness for removal of lead from not only aqueous solutions but also human body and traditional Chinese medicines. Here, functional kiwi peel composite, manganese dioxide decorated kiwi peel powder (MKPP), is proposed for the removal of Pb2+ effectively. The adsorption of Pb2+ in aqueous solution is a highly selective and endothermic process and kinetically follows a pseudo-second-order model, which can reach equilibrium with the capacity of 192.7 mg/g within 10 min. Comprehensive factors of hydration energy, charge-to-radius ratio and softness of Pb2+ make a stronger affinity between MKPP and Pb2+. The possible adsorption mechanism involves covalent bond, electrostatic force and chelation, etc. MKPP can be efficiently regenerated and reused with high adsorption efficiency after five cycles. Besides, MKPP can remove over 97% of Pb2+ from real water samples. MKPP can also alleviate lead poisoning to a certain extent and make the Pb level of TCM extract meet the safety standard. This work highlights that MKPP is a promising adsorbent for the removal of Pb2+ and provides an efficient strategy for reusing kiwi peel as well as dealing with the problem of Pb pollution.

How to achieve adequate quenching for DBP analysis in drinking water?

Quenching is an important step to terminate disinfection during preparation of disinfected water samples for the analysis of disinfection byproducts (DBPs). However, an incomplete quenching might result in continued reactions of residual chlorine, whereas an excessive quenching might decompose target DBPs. Therefore, an adequate quenching to achieve simultaneous disinfection termination and DBP preservation is of particular importance. In this study, the two-stage reaction kinetics of chlorine and three commonly used quenching agents (i.e., ascorbic acid, sodium thiosulfate, and sodium sulfite) were determined. Stopping quenching during the first stage prevented interactions of residual chlorine with natural organic matter. Complete quenching was achieved by minimizing the quenching time for ascorbic acid and sodium sulfite, while limiting the quenching time to less than 3 min for sodium thiosulfate. At the optimized quenching times, the molar ratios (MRs) of quenching agent to chlorine were 1.05, 1.10, and 0.75 for ascorbic acid, sodium sulfite, and sodium thiosulfate, respectively. The destructive effects of the three quenching agents on total organic halogen (TOX) followed the rank order of ascorbic acid (33.7-64.8 %) < sodium sulfite (41.6-72.8 %) < sodium thiosulfate (43.3-73.2 %), and the destructive effects on aliphatic DBPs also followed the rank order of ascorbic acid (29.5-44.5 %) < sodium sulfite (34.9-51.9 %) < sodium thiosulfate (46.9-53.2 %). For total organic chlorine (TOCl) and aliphatic DBPs, the quenching behavior itself had more significant destructive effect than the quenching agent type/dose and quenching time, but for total organic bromine (TOBr), the destructive effect caused by quenching agent type/dose and quenching time was more significant. High-dose, long-duration quenching enhanced the reduction of TOX, but had little effect on aliphatic DBPs. Additionally, the three quenching agents reduced the levels of halophenols (except for tribromophenol), while maintained or increased the levels of tribromophenol, halobenzoic/salicylic acids, and halobenzaldehydes/salicylaldehydes. To achieve adequate quenching for overall DBP analysis in chlorinated water samples, it is recommended to use ascorbic acid at a quenching agent-to-chlorine MR of 1.0 for a quenching time of < 0.5 h.

Microbial antagonistic mechanisms of Hg(II) and Se(IV) in efficient wastewater treatment using granular sludge.

The antagonistic effects of mercury (Hg) and selenium (Se) have been extensively studied in higher animals and plants. In this study, the microbial antagonistic effects of Hg and Se were utilized for wastewater treatment. We developed and optimized a new granular sludge approach to efficiently remove Hg(II) and Se(IV) from wastewater. Under anaerobic-oxic-anaerobic (AOA) conditions, the removal rates of Hg(II) and Se(IV) reached up to 99.91±0.07 % and 97.7 ± 0.8 %, respectively. The wastewater Hg(II) was mostly (97.43±0.01 %) converted to an inert mineral called tiemannite (HgSe) in the sludge, and no methylmercury (MeHg) was detected. The HgSe in sludge is less toxic, with almost no risk of secondary release, and it can be recovered with high purity. An inhibition experiment of mercury reduction and the high expression of the mer operon indicated that most Hg(II) (∼71 %) was first reduced to Hg0, and then Hg0 reacted with Se0 to synthesize HgSe. Metagenomic results showed that the final sludge (day 182) was dominated by two unclassified bacteria in the orders Rhodospirillales (27.7 %) and Xanthomonadales (6.3 %). Their metagenome-assembled genomes (MAGs) were recovered, suggesting that both of them can reduce Hg(II) and Se(IV). Metatranscriptomic analyses indicate that they can independently and cooperatively synthesize HgSe. In summary, granular sludge under AOA conditions is an efficient method for removing and recovering Hg from wastewater. The microbial transformation of Hg2+to Hg0 to HgSe may occur widely in both engineering and natural ecosystems.

Efficient treatment of veterinary pharmaceutical industrial wastewater by catalytic ozonation process: degradation of enrofloxacin via molecular ozone reactions.

The study focused on the efficacious performance of bimetallic Fe-Zn loaded 3A zeolite in catalytic ozonation for the degradation of highly toxic veterinary antibiotic enrofloxacin in wastewater of the pharmaceutical industry. Batch experiments were conducted in a glass reactor containing a submerged pump holding catalyst pellets at suction. The submerged pump provided the agitation and recirculation across the solution for effective contact with the catalyst. The effect of ozone flow (0.8-1.55 mg/min) and catalyst dose (5-15 g/L) on the enrofloxacin degradation and removal of other conventional pollutants COD, BOD5, turbidity was studied. In batch experiments, 10 g of Fe-Zn 3A zeolite efficiently removed 92% of enrofloxacin, 77% of COD, 69% BOD5, and 61% turbidity in 1 L sample of pharmaceutical wastewater in 30 min at 1.1 mg/min of O3 flow. The catalytic performance of Fe-Zn 3A zeolite notably exceeded the removal efficiencies of 52%, 51%, 52%, and 59% for enrofloxacin, COD, BOD5, and turbidity, respectively, achieved with single ozonation process. Furthermore, an increase in the biodegradability of treated pharmaceutical industrial wastewater was observed and made biodegradable easily for subsequent treatment.

Reliability of organic and biogenic pollutant removal in selected technologies used in domestic wastewater treatment plants: A comparative analysis.

The results of a comparative study of two different technological solutions applicable to decentralised domestic wastewater treatment systems are presented. A hybrid reactor with activated sludge and mobile biofilm carriers moving in wastewater is one of them, and an innovative quasi-technical combination of a biological reactor with a sprinkled bed filled with sintered clay granules, followed in the process line by an innovative slope type filtration bed, is the other one. The study has shown a significant advantage of filter bed installations in functional quality, expressed in low values of indicators and pollutant concentrations. In the comparison of technological reliability and probability of exceeding the requirement values of BOD5 = 40 mg/L, Facility 1 achieved technological reliability of 70% and probability of exceeding was 23%. Technological reliability of Facility 2 in this component was 100% and P = 0%. Both facilities presented 100% technological reliability in the COD indicators, with zero probability of exceeding the required value of 150 mg/L. The reliability of TSS removal was similarly high in both facilities: 91% and 100%. The higher functional quality of Facility 2 was evident in TN and PO4-P parameters, where the period of its operation with exceeded values did not exceed 20% and 13%, respectively, with a low probability of exceeding the value of 18% and 2.5%, respectively. However, Facility 1 was unreliable in this regard in 90% and 84%, with a very high probability of exceeding the required values of these parameters: 88% and 72%. This facility does not meet the required criteria in this respect and may cause a risk to the aquatic environment if wastewater is discharged directly into open watercourses, or if it enters shallow groundwater. The use of a suitable, biologically active soil-plant receiver can eliminate this risk.

Release characteristics and risk assessment of volatile sulfur compounds in a municipal wastewater treatment plant with odor collection device.

Due to the malodorous effects and health risks of volatile sulfur compounds (VSCs) emitted from wastewater treatment plants (WWTPs), odor collection devices have been extensively utilized; however, their effectiveness has rarely been tested. In the present investigation, the characteristics of VSCs released in a WWTP equipped with gas collection hoods are methodically examined by gas chromatography. The obtained results indicate that the concentration of VSCs in the ambient air can be substantially reduced, and the primary treatment unit still achieves the highest concentration of VSCs. Compared to WWTPs without odor collection devices, the concentration of H2S in this WWTP is not dominant, but its sensory effects and health risks are still not negligible. Additionally, research on the emission of VSCs from sludge reveals that the total VSCs emitted from dewatering sludge reaches the highest level. Volatile organic sulfur compounds play a dominant role in the component and sensory effects of VSCs released by sludge. This study provides both data and theoretical support for analyzing the effectiveness of odor collection devices in WWTPs, as well as reducing the source of VSCs. The findings can be effectively employed to optimize these devices and improve their performance.

Global research trends of uranium-containing wastewater treatment based on bibliometric review.

The generation of uranium-containing wastewater (UCW) during different stages of uranium mining, processing, and utilization presents a significant ecological and biospheric threat. Consequently, it is crucial for both sustainable development and the protection of human health to adopt appropriate methods for the treatment of UCW as well as the separation and enrichment of uranium. This study conducted a comprehensive search of the Web of Science Core Collection (WOSCC) database for publications related to UCW treatment between 1990 and 2022 to gain insight into current trends in the field. Subsequently, the annual publications, WOSCC categories, geographical distribution, major collaborations, prolific authors, influential journals, and highly cited publications were the subjects of a biliometric analysis that was subsequently carried out. The study findings indicate a significant rise in the overall number of publications in the research field between 1990 and 2022. China, India, and the USA emerged as the primary contributors in terms of publication count. The Chinese Academy of Sciences, the East China University of Technology, and the University of South China were identified as the key research institutions in this field. Furthermore, a majority of the publications in this field were distributed through prestigious journals with high impact factors, such as the Journal of Radioanalytical and Nuclear Chemistry. The top 3 journals were Radioanalytical and Nuclear Chemistry, Chemical Engineering Journal, and Journal of Hazardous Materials. The keyword co-occurrence and burst analysis revealed that the current research on UCW treatment mainly focuses on adsorption-based treatment methods, environmentally functional materials, uranium recovery, etc. Furthermore, the study of the adsorption efficiency of different adsorbent materials, as well as the strengthening and improvement of adsorbent material selectivity and capacity for the recovery of uranium, represents a research hotspot in the field of UCW treatment in the future. This study conducts a comprehensive overview of the current status and prospects of the UCW treatment, which can provide a valuable reference for gaining insights into the development trajectory of the UCW treatment.

A novel physical-biochemical treatment of refinery wastewater.

As of 2022, China has achieved a crude oil processing capacity of 918 million tons, leading to a notable escalation in the production of refinery wastewater. The composition of refinery wastewater is intricate and diverse, posing a substantial challenge to its treatment. In order to facilitate appropriate discharge or reuse, an exhaustive separation process is imperative for refinery wastewater. Conventional pre-treatment processes typically employ inclined plate separators and dissolved air flotation (DAF) for the removal of oil and suspended solids (SS), while sequencing batch reactor (SBR), oxidation ditch, or biological aerated filter (BAF) are employed for the biological treatment process. However, these approaches encounter challenges such as a large spatial footprint, suboptimal treatment efficiency, and high energy consumption. In response to these challenges, this study introduces a novel integrated apparatus consisting of a high-efficiency oil remover (HEOR), coalescence oil remover (COR), and an airlift-enhanced loop bioreactor (AELR). A pilot-scale test was conducted to evaluate the performance of this integrated system in practical field applications. The pilot-scale tests reveal that, without the addition of chemical agents, the petroleum removal efficiency of "HEOR + COR" system was 1.2 times that of DAF. Compared with the SBR system, AELR's volume loading was increased by 1.56 times. The effluent quality achieved in the pilot-scale tests attained parity with that the original process. The "HEOR + COR + AELR" system exhibited energy and carbon emissions reduction of 28% and 30% compared to the "DAF + SBR" system, respectively. Therefore, the operating costs was reduced by approximate 1 Chinese Yuan (CNY) per ton of treated water. This technological advancement serves as a valuable reference for the implementation of low-carbon treatment of refinery wastewater.

Strategies for livestock wastewater treatment and optimised nutrient recovery using microalgal-based technologies.

Global sustainable development faces several challenges in addressing the needs of a growing population. Regarding food industries, the heightening pressure to meet these needs has resulted in increased waste generation. Thus, recognising these wastes as valuable resources is crucial to integrating sustainable models into current production systems. For instance, the current 24 billion tons of nutrient-rich livestock wastewater (LW) generated yearly could be recovered and valorised via biological uptake through microalgal biomass. Microalgae-based livestock wastewater treatment (MbLWT) has emerged as an effective technology for nutrient recovery, specifically targeting carbon, nitrogen, and phosphorus. However, the viability and efficacy of these systems rely on the characteristics of LW, including organic matter and ammonium concentration, content of suspended solids, and microbial load. Thus, this systematic literature review aims to provide guidance towards implementing an integral MbLWT system for nutrient control and recovery, discussing several pre-treatments used in literature to overcome the challenges regarding LW as a suitable media for microalgae cultivation.

An integrated approach for wastewater treatment and algae cultivation: Nutrient removal analysis, biodiesel extraction, and energy and environmental metrics enhancement.

Human urine is rich in nitrogen and phosphorus, and the presence of these elements in wastewater significantly disrupts the biogeochemical cycle. Meanwhile, green algal biomass cultivation is unfeasible without these nutrients. Hence, the present study integrates wastewater treatment and algae cultivation to extract biodiesel and improve its performance through fuel modification. Chlorella vulgaris algae was cultivated in different dilution ratios of water and urine, and the nutrient removal rate was analyzed. Chlorella vulgaris algae biodiesel (CAB) was derived through Bligh and Dyer's method followed by transesterification, and its functional and elemental groups were analyzed. The various volume concentrations of CAB were blended with regular diesel fuel (RDF), and 10% water was added to a 30% CAB blended RDF to evaluate the combustion performance and environmental impacts. The results of the experiments demonstrated that the algae cultivation effectively removed the wastewater nutrients. The functional and elemental groups of CAB are identical to those of RDF. The engine characteristics of test fuels report that the CAB-blend RDF fuel mixtures generate low carbon footprints, whereas negative impacts have been drawn for performance metrics and oxides of nitrogen emissions. The water-emulsified fuel outweighed the unfavorable effects and promoted more efficient and cleaner combustion.

Occurrence and distribution of azole antifungal agents in eight urban Romanian waste water treatment plants.

Azole compounds are utilized to combat fungal infections in plants to protect them and also used for treating mycosis in humans. The LC-MS/MS method is a technique that combines liquid chromatography with tandem mass spectrometry for analysis of twelve azole compounds from wastewater (influent, effluent) and sewage sludge. The compounds were isolated from waste water using automatic extraction in the solid phase. Sludge samples were dried by lyophilization, after which they were subjected to ultrasound extraction with methanol. The quantification limits ranged from 0.3 ng/L (clotrimazole-CLO and prochloraz-PRO) to 1.5 ng/L (tetraconazole-TEB and penconazole-PEN), for wastewater samples and for sewage sludge, the LOQs ranged from 0.1 ng/g to 0.6 ng/g. High concentrations of climbazole-CLI (207-391 ng/L), tebuconazole (92-424 ng/L), and clotrimazole (6.9-93-ng/L) were observed in influent samples of the 8 urban wastewater treatment plants, followed by fluconazole (49.3-76.8 ng/L), and prochloraz (7.3-72 ng/L). The ∑Azoles had a maximum of 676 ng/L in the Galati effluent, followed by the Bucharest station 357 ng/L, and 345 ng/L in the Braila effluent. The highest value of the daily mass loading (input) level was observed for climbazole, 265 mg/day/1000 in Iasi station, followed by tebuconazole, 238 mg/day/1000 people in the Bucharest station, and 203 mg/day/1000 people for climbazole in the Targoviste station. The daily mass emission presented values between 0.7 and 247 mg/day/1000 people. The highest emissions were observed for climbazole, 247 mg/day/1000 people in Braila station; 174 mg/day/1000 people in the Iasi station and 129 mg/day/1000 people in the Bucharest station. The concentrations of climbazole detected in the effluent can present a high risk for the plants Lemna minor and Navicula pelliculosa. Clotrimazole may present a high risk to the plant Desmodesmus subspicatus and to the invertebrate Daphnia magna. PRO may present high risk to the invertebrate Mysidopsis Bahia.

Biomimetic ZrO2-modified seaweed residue with excellent fluorine/ bacteria removal and uranium extraction properties for wastewater purification.

Exploring and developing promising biomass composite membranes for the water purification and waste resource utilization is of great significance. The modification of biomass has always been a focus of research in its resource utilization. In this study, we successfully prepare a functional composite membrane, activated graphene oxide/seaweed residue-zirconium dioxide (GOSRZ), with fluoride removal, uranium extraction, and antibacterial activity by biomimetic mineralization of zirconium dioxide nanoparticles (ZrO2 NPs) on seaweed residue (SR) grafted with oxidized graphene (GO). The GOSRZ membrane exhibits highly efficient and specific adsorption of fluoride. For the fluoride concentrations in the range of 100-400 mg/L in water, the removal efficiency can reach over 99 %, even in the presence of interfering ions. Satisfactory extraction rates are also achieved for uranium by the GOSRZ membrane. Additionally, the antibacterial performance studies show that this composite membrane efficiently removes Escherichia coli (E. coli) and Methicillin-resistant Staphylococcus aureus (MRSA). The high adsorption of F- and U(VI) to the composite membrane is ascribed to the ionic exchange and coordination interactions, and its antibacterial activity is caused by the destruction of bacterial cell structure. The sustainability of the biomass composite membranes is further evaluated using the Sustainability Footprint method. This study provides a simple preparation method of biomass composite membrane, expands the water purification treatment technology, and offers valuable guidance for the resource utilization of seaweed waste and the removal of pollutants in wastewater.

First application of the novel anaerobic/aerobic/anoxic (AOA) process for advanced nutrient removal in a wastewater treatment plant.

The stringent effluent quality standards in wastewater treatment plants (WWTPs) can effectively mitigate environmental issues such as eutrophication by reducing the discharge of nutrients into water environments. However, the current wastewater treatment process often struggles to achieve advanced nutrient removal while also saving energy and reducing carbon consumption. The first full-scale anaerobic/aerobic/anoxic (AOA) system was established with a wastewater treatment scale of 40,000 m3/d. Over one year of operation, the average TN and TP concentration in the effluent of 7.53 ± 0.81 and 0.37 ± 0.05 mg/L was achieved in low TN/COD (C/N) ratio (average 5) wastewater treatment. The post-anoxic zones fully utilized the internal carbon source stored in pre-anaerobic zones, removing 41.29 % of TN and 36.25 % of TP. Intracellular glycogen (Gly) and proteins in extracellular polymeric substances (EPS) served as potential drivers for post-anoxic denitrification and phosphorus uptake. The sludge fermentation process was enhanced by the long anoxic hydraulic retention time (HRT) of the AOA system. The relative abundance of fermentative bacteria was 31.66 - 55.83 %, and their fermentation metabolites can provide additional substrates and energy for nutrient removal. The development and utilization of internal carbon sources in the AOA system benefited from reducing excess sludge production, energy conservation, and advanced nutrient removal under carbon-limited. The successful full-scale validation of the AOA process provided a potentially transformative technology with wide applicability to WWTPs.

Paradigm shift in Nutrient-Energy-Water centered sustainable wastewater treatment system through synergy of bioelectrochemical system and anaerobic digestion.

With advancements in research and the necessity of improving the performance of bioelectrochemical system (BES), coupling anaerobic digestion (AD) with BES is crucial for energy gain from wastewater and bioremediation. Hybridization of BES-AD concept opens new avenues for pollutant degradation, carbon capture and nutrient-resource recovery from wastewater. The strength of merging BES-AD lies in synergy, and this approach was employed to differentiate fads from strategies with the potential for full-scale implementation and making it an energy-positive system. The integration of BES and AD system increases the overall performance and complexity of combined system and the cost of operation. From a technical standpoint, the primary determinants of BES-AD feasibility for field applications are the scalability and economic viability. High potential market for such integrated system attract industrial partners for more industrial trials and investment before commercialization. However, BES-AD with high energy efficacy and negative economics demands performance boost.

Release of phosphorus through pretreatment of waste activated sludge differs essentially from that of carbon and nitrogen resources: Comparative analysis across four wastewater treatment facilities.

The accumulation of phosphorus in activated sludge in wastewater treatment plants (WWTPs) provides potential for phosphorus recovery from sewage. This study delves into the potential for releasing phosphorus from waste activated sludge through two distinct treatment methods-thermal hydrolysis and pH adjustment. The investigation was conducted with activated sludge sourced from four WWTPs, each employing distinct phosphorus removal strategies. The findings underscore the notably superior efficacy of pH adjustment in solubilizing sludge phosphorus compared to the prevailing practice of thermal hydrolysis, widely adopted to enhance sludge digestion. The reversibility of phosphorus release within pH fluctuations spanning 2 to 12 implies that the release of sludge phosphorus can be attributed to the dissolution of phosphate precipitates. Alkaline sludge treatment induced the concurrent liberation of COD, nitrogen, and phosphorus through alkaline hydrolysis of sludge biomass and the dissolution of iron or aluminium phosphates, offering potential gains in resource recovery and energy efficiency.

Sustained Phosphorus Removal and Enrichment through Off-Flow Desorption in a Reservoir of Membrane Capacitive Deionization.

In this study, we used a membrane capacitive deionization device with a reservoir (R-MCDI) to enrich phosphorus (P) from synthetic wastewater. This R-MCDI had two small-volume electrode chambers, and most of the electrolyte was contained in the reservoir, which was circulated along the electrode chambers. Compared with conventional MCDI, R-MCDI exhibited a phosphate removal rate of 0.052 µmol/(cm2·min), approximately double that of MCDI. This was attributed to R-MCDI's utilization of OH- alternative adsorption to remove phosphate from the influent. Noticing that around 73.9% of the removed phosphate was stored in the electrolyte in R-MCDI, we proposed a novel off-flow desorption operation to enrich the removed phosphate in the reservoir. Exciting results from the multicycle experiment (∼8 h) of R-MCDI showed that the PO43--P concentration in the reservoir increased all the way from the initial 152 mg/L to the final 361 mg/L, with the increase in the P charge efficiency from 5.5 to 22.9% and the decrease in the energy consumption from 28.2 to 6.8 kW h/kg P. The P recovery performance of R-MCDI was evaluated by viewing other similar studies, which revealed that R-MCDI in this study achieved superior P enrichment with low energy consumption and that the off-flow desorption proposed here considerably simplified the operation and enabled continuous P enrichment.

An integrated physical-chemical system for concurrent carbon, nitrogen, and phosphorus removal in municipal wastewater treatment plants.

A substantial quantity of suspended solids (SS) present in municipal wastewater leads to the swift depletion of the ion exchange (IE) capacity of natural zeolites like Clinoptilolite (CIO). This limitation has become the primary factor contributing to the limited adoption of the IE technique within municipal wastewater treatment plants (WWTPs). However, an extensive lab-scale and pilot-scale study conducted over approximately one year has made it possible to efficiently apply the IE system using CIO (main grain size of 0.5-1.0 mm) upstream of the primary sedimentation tank (PST). The primary treated wastewater (PTWW) was introduced to the IE system either by pre-straining or without any pre-treatment. The IE system's capabilities for removing total suspended solids (TSS), chemical oxygen demand (COD), and phosphorus (P) while primarily focusing on ammonium (NH4+) recovery were undergone for a detailed investigation. Frequent backwashing, involving intermittent water and air injection, was used to mitigate clogging as the main problem of the IE system for treating PTWW. The results revealed a mean removal efficiency of 85 %, 60 %, 50 %, and 30 % for NH4+, TSS, TCOD, and total phosphorus (TP), respectively, per cycle exclusively for the IE system. As the system scaled up, a substantial reduction was observed in the adsorption capacity, shifting from approximately 12 to 1 g NH4+ (kgCIO)-1. Despite this drawback, the study's finding showed that prolonged treatment of PTWW for NH4+ removal and recovery in municipal WWTPs, besides substantially reducing carbonaceous pollutants, is applicable. Implementing this application will not only decrease the biological treatment costs for municipal wastewater but also yield valuable by-products, such as NH4Cl, which can serve as a foundational material for the production of ammonium chloride fertilizer. Therefore, transitioning to IE systems in municipal WWTPs will diminish the reliance on resource-intensive methods like the Harber-Bosch procedure for producing nitrogen fertilizer.