Existing Wastewater Treatment Plants Research Articles

Natural compound-induced downregulation of antimicrobial resistance and biofilm-linked genes in wastewater Aeromonas species.

Addressing the global antimicrobial resistance (AMR) crisis requires a multifaceted innovative approach to mitigate impacts on public health, healthcare and economic systems. In the complex evolution of AMR, biofilms and the acquisition of antimicrobial resistance genes (ARGs) play a pivotal role. Aeromonas is a major AMR player that often forms biofilm, harbors ARGs and is frequently detected in wastewater. Existing wastewater treatment plants (WWTPs) do not have the capacity to totally eliminate antimicrobial-resistant bacteria favoring the evolution of ARGs in wastewater. Besides facilitating the emergence of AMR, biofilms contribute significantly to biofouling process within the activated sludge of WWTP bioreactors. This paper presents the inhibition of biofilm formation, the expression of biofilm-linked genes and ARGs by phytochemicals andrographolide, docosanol, lanosterol, quercetin, rutin and thymohydroquinone. Aeromonas species were isolated and purified from activated sludge samples. The ARGs were detected in the isolated Aeromonas species through PCR. Aeromonas biofilms were quantified following the application of biocompounds through the microtiter plate assay. qPCR analyses of related genes were done for confirmation. Findings showed that the natural compounds inhibited the formation of biofilms and reduced the expression of genes linked to biofilm production as well as ARGs in wastewater Aeromonas. This indicates the efficacy of these compounds in targeting and controlling both ARGs and biofilm formation, highlighting their potential as innovative solutions for combating antimicrobial resistance and biofouling.

Evaluation of Sanitation Technologies Across Sanitation Service Chain in Kericho Town, Kenya

In 2020, over half of the world's population resided in cities, with projections indicating that by 2050, this figure will rise to 70%. Providing adequate sanitation services in urban and peri-urban areas presents significant challenges due to the dense concentration of people, particularly in low- and middle-income countries. Poor sanitation practices in these areas can lead to the spread of diseases with high morbidity and mortality rates. The focus of the study was on Kericho town, Kenya, facing a notable sanitation challenge due to dilapidated sewer system and inadequate sanitation facilities . The aim of this study was to evaluate the safety of sanitation technologies used in Kericho Town. Descriptive study design was adopted. Data collection methods included surveys, interviews, and observations, with a sample size of 409 households. The findings revealed that 66.5% of the population relies on pit latrines with slabs, 13.69% use pour/manual flush systems, 11.49% have ventilated improved pit latrines, 8.07% employ automatic cistern flush, and a minimal 0.24% practice open defecation. 25% of population discharged waste directly into the sewerage system whereby 5% were considered safely managed. Additionally, 4% of waste from user interfaces was discharged directly into open ground or open drains. 2% of population used septic tanks connected to soak pits, whereas 6% of population used septic tanks connected to open ground. Sludge from septic tanks, comprising 20%, was delivered to the WWTP by exhausters for further treatment, of which only 20% underwent treatment, with the remainder released untreated into the environment. 49% of the population used lined pits, while 14% used unlined pits. Approximately 20% of faecal sludge from the pits was exhausted, with only 20% of it considered safely treated, and the remainder released into the environment. Notably, open defecation accounted for less than 1% based on the survey findings. Consequently, the current trend in faecal sludge management in Kericho Town posed potential health hazards to the community unless measures such as rehabilitating the existing wastewater treatment plant are implemented.

A Dataset of Distribution and Characterization of Underground Wastewater Treatment Plants in China

Underground wastewater treatment plants (U-WWTPs) have emerged as a novel paradigm for urban wastewater pollutants management, offering benefits such as alleviating the Not-in-my-backyard (NIMBY) effect and utilizing land resources efficiently. China stands at the forefront, witnessing swift advancements in U-WWTP technology and deployment. However, the absence of a thorough understanding of their geographical distribution and operational characteristics could lead to misaligned planning and construction, resulting in inefficient resource allocation and treatment capacities for urban wastewater treatment. This dataset provides an up-to-date overview of the spatial distribution, process selection, and discharge standards for all U-WWTPs in China (with a total number of 201) constructed since 1995. To enhance comparative analysis, the dataset has been supplemented with information on conventional aboveground wastewater treatment plants (A-WWTPs), comprising a total of 2464 records, which enriches a more comprehensive evaluation of different wastewater treatment approaches. Utilizing this dataset can provide essential data support for the strategic management of urban wastewater systems and serve as a valuable reference for the paradigmatic renovation of existing wastewater treatment plants.

Enhancing ozonation technology: A case study on full-scale airlift reactor upgrades in the existing wastewater treatment plant's ozonation tank using CFD

Traditional pneumatic bubble column reactors (PBCRs) in wastewater treatment often have limitations in ozone distribution and disinfection efficacy. This study introduces an optimized Airlift Reactor (ALR) design, enhanced with Computational Fluid Dynamics (CFD), to improve ozone contact time and uniform distribution. Tailored for the SONATRACH GP1/Z Complex in Bethioua, Algeria, the ALR addresses the treatment needs of the facility's WWTP Phase-1, handling domestic wastewater. The study is unique for its full-scale implementation of the ALR, as previous research focused on lab-scale cases. Advanced CFD simulations optimized the ALR design, focusing on baffle configurations to enhance ozone disinfection. The upgraded One Side Baffled Airlift (OS-BALR) variant achieved a Total Coliform inactivation rate of 94.52 %, compared to 74 % with the traditional design. The OS-BALR also demonstrated a lower ozone mass transfer coefficient (KLa) of 0.0048 s−1, improving treatment efficiency and reducing energy consumption. While the Baffled Bubble Column (BBC) reactor showed a higher KLa of 0.0055 s−1 and a microbial removal efficacy of 96.12 %, it is more energy-intensive. This study advances wastewater treatment by bridging innovation with industrial application, contributing to sustainable wastewater management practices globally.

Enhancing simultaneous nitrification and denitrification in a plant-scale integrated fixed-film activated sludge system: Focusing on the cooperation between activated sludge and biofilm

To further remove nutrients through simultaneous nitrification and denitrification (SND), the integrated fixed-film activated sludge (IFAS) system has become one of the most efficient pathways for modifying the existing wastewater treatment plants. This study investigated the cooperation between suspended activated sludge and carrier-attached biofilm for promoting SND in different seasons in a plant-scale IFAS system. The results showed that the involvement of biofilm could stimulate SND, removing 23.9 % of influent total nitrogen (TN) in the aerobic IFAS system. The nitrification rate and the SND ratio were much influenced by the temperature, resulting in higher TN removal efficiency in summer (90.3 %) than that in winter (86.4 %). The highest SND ratio of 67 % could be achieved at the temperature of 23 °C. Additionally, the SND ratio also depended on a variety of operational parameters (such as dissolved oxygen (DO), COD/NH4+-N, and mixed liquor suspended solids (MLSS)). High-throughput sequencing technology further confirmed that the composition of the functional bacterial communities in activated sludge significantly differed from that in biofilm. Nitrifying bacteria were mostly detected in biofilm samples, while more denitrifying bacteria existed in activated sludge, thus resulting in the enhancement of synergic nitrogen removal via SND in the IFAS system.

Mercury Discharge Inventory Based on Sewage Treatment Process in China

Mercury pollution is a serious public health problem. China’s extensive use and reliance on mercury has led to water pollution, particularly the presence of methylmercury in water. Estimating total mercury emissions from wastewater in China is challenging due to the large amount and wide range of emissions. An estimation model for total mercury content in sewage in China was established by establishing a relationship between sewage treatment volume, mercury content in effluent after sewage treatment, and the data of sludge production and mercury content in the sewage treatment plant. It was determined that only 3% of mercury entered the air during sewage treatment, 27.5% of mercury entered the effluent, and about 69.5% of mercury entered the sludge, based on the treatment of existing wastewater treatment plants in China. From 2002 to 2021, the average annual sewage mercury emission in China was 32.07 Mg, and the emissions were higher in densely populated and economically developed provinces such as Beijing, Shandong, Hebei, and Guangdong. By 2025, China’s mercury emissions are projected to reach 55.41 Mg. By 2035, China’s mercury emissions are projected to reach 49.3 Mg.

Assessment of three different approaches for integrating phosphorus recovery from sewage sludge and derived products in existing wastewater treatment plants

Three different technological solutions, namely acidogenic fermentation and chemical extraction (alkaline or acidic), followed by precipitation with 1% Ca(OH)2, were investigated in the view of integrating phosphorus recovery into existing wastewater treatment plants. Experiments were conducted at the lab-scale using (i) sludge taken from biologically and chemically promoted phosphorus removal activated sludge processes and (ii) ashes obtained from sludge muffle incineration. Results highlighted the benefits of enhanced biological phosphorus removal (EBPR) systems rather than chemically promoted phosphorus removal in not only phosphorus extraction (up to 40% with EBPR) and recovery directly from secondary sludge (P precipitation between 66 and 92%), but after sludge incineration as well (P extraction up to 96% and precipitation above 96%). Acidogenic fermentation ensured the highest phosphorus release from EBPR sludge (equal to a concentration in solution of 122 mg/L P-PO43−), while the derived ashes had a lower level of metal contamination (particularly Fe and Al content < 2%). The phosphorus-rich product obtained by means of the recovery process showed relevant metal contamination (Cu, Zn, and Ni) under some operating conditions, suggesting the need for further treatments.

Precision and Accuracy Limits of Wastewater-Based Epidemiology—Lessons Learned from SARS-CoV-2: A Scoping Review

Background: Wastewater-based epidemiology (WBE) has become crucial for early microbial outbreak detection and public health surveillance globally, underscored by the COVID-19 pandemic. However, despite advancements in sampling and analyses, interpreting results and estimating infection rates pose challenges. Enhancements in sewer system engineering, understanding the wastewater environment, and addressing the impact of the environment on the accuracy of results are needed. Objective: This scoping review aims to identify engineering knowledge gaps in WBE to guide future study designs. Design: Research on “wastewater-based epidemiology” involving “engineering”, published between 2015 and 2023, was extracted from the Scopus database. Results: This scoping review examines elements influencing WBE’s precision and reliability, especially in identifying and measuring SARS-CoV-2 RNA. It identifies significant effects of engineering, analytical practices, and the wastewater’s composition on WBE performance. Conclusions: This review calls for further investigation into economical evaluation methods of these factors to enhance WBE data normalization and interpretation, utilizing existing wastewater treatment plant data used for treatment control, which could be a cost-effective approach over more expensive population biomarkers. This approach, aside from SARS-CoV-2, holds potential for application to a broader number and types of diseases, as well as population consumption habits.

Utilizing anaerobic substrate distribution for growth of aerobic granular sludge in continuous-flow reactors

The development of continuous flow reactors (CFRs) employing aerobic granular sludge (AGS) for the retrofit of existing wastewater treatment plants (WWTPs) using a continuous-flow activated sludge (CFAS) system has garnered increasing interest. This follows the worldwide adoption of AGS technology in sequencing batch reactors (SBRs). The better settleability of AGS compared to AS allows for process intensification of existing wastewater treatment plants without the difficult conversion of often relatively shallow CFRs to deeper AGS-SBRs.To retrofit existing CFAS systems with AGS, achieving both increased hydraulic capacity and enhanced biological nutrient removal necessitates the formation of granular sludge based on the same selective pressures applied in AGS-SBRs. Previous efforts have focussed mainly on the selective wasting of flocculent sludge and retaining granular sludge to drive aerobic granulation.In this study a pilot-scale CFR was developed to best mimic the implementation of the granulation mechanisms of full-scale AGS-SBRs. The pilot-scale reactor was fed with pre-settled municipal wastewater. We established metrics to assess the degree to which the proposed mechanisms were implemented in the pilot-scale CFR and compared them to data from full-scale AGS-SBRs, specifically with respect to the anaerobic distribution of granule forming substrates (GFS). The selective pressures for granular sludge formation were implemented through inclusion of anaerobic upflow selectors with a water depth of 2.5 meters, which yielded a sludge with properties similar to AGS from full-scale SBRs. In comparison to the CFAS system at Harnaschpolder WWTP treating the same pre-settled wastewater, a more than twofold increase in volumetric removal capacity for both phosphorus and nitrogen was achieved. The use of a completely mixed anaerobic selector, as opposed to an anaerobic upflow selector, caused a shift in EBPR activity from the largest towards the smallest size class, while nitrification was majorly unaffected. Anaerobic selective feeding via bottom-feeding is, therefore, favorable for the long-term stability of AGS, especially for less acidified wastewater. The research underlines the potential of AGS for enhancing the hydraulic and biological treatment capacity of existing CFAS systems.

Aerobic granulation in a continuous-flow simultaneous nitrification, endogenous denitrification, and phosphorus removal system fed with low-strength wastewater: Granulation mechanism and microbial succession

The culture of aerobic granular sludge (AGS) in continuous-flow system for treating low-strength municipal wastewater is still a challenge for its widespread application. This study developed a continuous-flow reactor based on metabolic and hydraulic selection pressure to explore the feasibility of culturing AGS in conventional continuous-flow mode. The results showed that aerobic granulation was successfully achieved with a mean particle size of 373 μm and almost all granules (95.6 %) were larger than 200 μm. An obvious three-stages granulation process comprised of initial adhesion, the formation of early aggregates that acted as nuclei of granules, and the final AGS maturation, was observed in this work. The selective enrichment of slow-growing bacteria in alternating feast/famine condition played a critical role in the aerobic granulation. The analysis results of extracellular polymeric substances revealed that β-polysaccharides and proteins distributed uniformly within the mature granules, while α-polysaccharides were found mainly concentrated around the granules, which was believed to enhance the mechanical strength of granules. The continuous-flow AGS system exhibited an excellent simultaneous carbon, nitrogen, and phosphorus removal performance with high removal efficiencies of NH4+-N (97.6 %), TIN (91.0 %), COD (93.7 %), and TP (94.8 %). Moreover, a low sludge yield of 0.1 gMLSS/gCOD was obtained for dramatic in situ sludge reduction. Illumina MiSeq sequencing results confirmed the outstanding accumulation of GAOs (Candidatus_Competibacter) and PAOs (Rhodocyclaceae) in the system, which were responsible for simultaneous C, N, P removal and sludge reduction. Overall, this study demonstrated the feasibility of aerobic granulation in conventional continuous-flow mode and offered insights into the granulation mechanism, providing implications and references for the application of AGS technology in existing wastewater treatment plants.

Enhancement of energy and cost efficiency in wastewater treatment plants using hybrid bio-inspired machine learning control techniques

Global population growth drives demand for clean water, energy, and wastewater production in urban areas. Most existing wastewater treatment plants (WWTPs) are energy- and cost-intensive. To achieve the UN Sustainable Development Goals (SDGs) by 2030, many regions have implemented strict policies for energy consumption and contaminated water discharge, promoting environmental sustainability. This paper attempts to enhance the achievement of SDGs in the wastewater treatment industry by proposing a novel method for hierarchical control of wastewater treatment plants to ensure energy and cost efficiency with less knowledge of the process model, fewer measurements, and fewer control loops. This controller is the combination of a machine learning control technique with a bio-inspired computational algorithm. To evaluate and validate the performance of the proposed controller on the WWTP, the benchmark simulation model no. 1 (BSM1) has been used. The most significant contributions of this paper show that 488.96 KWh/d, 3620.08 Kg/d, and 3454.55 KWh/d of aeration energy cost index, sludge production cost index, and operational cost index are respectively saved when compared to the default control strategy (DCS). Also, 893.69 Kg pollution units per day of effluent fine-related costs have been successfully recovered when compared to the DCS. The experimental results illustrate that the proposed control yields significant amelioration of the energy and cost profile of the WWTP with no effluent violation in dry, rain, and storm weather conditions.

Performance and life cycle assessment of moving-bed biofilm and integrated fixed-film reactors to upgrade activated sludge systems

Upgrading the capacity of existing wastewater treatment plants (WWTPs) is hindered by the limited space for extension. This matter is particularly crucial in developing countries where dense urban areas experience unexpectedly growing populations. Herein, we study the capacity upgrading of a WWTP working by a conventional activated sludge (CAS) system from 180,000 m3/d to 240,000 and 300,000 m3/d. The WWTP case study focuses on a large plant in Mansoura, Egypt, requiring capacity upgrades to accommodate population growth. For this purpose, we used mathematical modeling to simulate current and suggested WWTP designs. Moving bed biofilm reactor (MBBR) and integrated fixed film-activated sludge (IFAS) systems were designed to increase the WWTP capacity to 240,000 and 300,000 m3/d by the addition of plastic biofilm carrier to 25% and 50% of the aeration basins, respectively. IFAS outperformed conventional and MBBR systems in terms of BOD, COD, TSS, NH4, TP, and PO4, in addition to increased capacity. We moreover used life cycle assessment (LCA) to comprehend the environmental favorability of upgrading scenarios. The most affected environmental categories are global warming and eutrophication due to the operation stage (especially electricity). Global warming potential for CAS, MBBR, and IFAS (300,000 m3/d) are 2.19, 1.69, and 1.73 kg CO2 eq respectively. Eutrophication potential for CAS, MBBR, and IFAS (300,000 m3/d) are 0.0025, 0.0022, and 0.0017 kg PO4- eq respectively. We also estimated the amortization and running costs for various upgrading scenarios, providing an integrated analysis for decision-making purposes.

Geospatial Approaches to Improve Water Availability through Demand Assessment in Agriculture Based on Treated Wastewater: A Case Study of Weinstadt, Baden-Württemberg

The sustainable management of water scarcity is a globally crucial issue. Germany has established efficient water management systems, but the agricultural sector still struggles with water scarcity as the demand surpasses the available water supply. In this work, the primary aim was to establish a framework for making water accessible for irrigation and additional use in households through the effective utilization of recycled water from wastewater treatment facilities. The research inquiries were focused on evaluating the changes in the CROPWAT agricultural irrigation model, determining the spatial distribution of zonal severity, estimating the capacity of urban roof catchments, and evaluating the economic value addition of retreated water from the existing wastewater treatment plant supply. According to the findings, the annual amount of water required for agriculture in the designated study location is approximately 2.9 million m3. Although there is no initial need for irrigation water, the demand for irrigation water increases during the development, active growth, and mature stages of maize, winter wheat, and wine grapes, reaching around 189 mm, 223 mm, and 63 mm, respectively. According to our observations, the annual water supply in Weinstadt is around 4 million m3. On the other hand, the compensated volume of water to the current water supply calculated from the urban roof rainfall is estimated to be 0.8 million m3, which is considered valuable from an economic standpoint. This economically efficient volume of water would reduce the current treated water supply, which indicates an opportunity for enhanced agricultural irrigation.

The influence of seasonality on the technological parameters of biological wastewater treatment at existing wastewater treatment plants

The work carried out monitoring of the process of biological treatment of municipal and industrial wastewater at operating wastewater treatment plants in months that differ in temperature and flow rate of process influent. The analysis of wastewater pollution indicators was carried out at three main points of the process line (receiving chamber, settling tank and Venturi tray) with a sampling frequency of 1 every 5 days. It was found that in March and April, the flow rate of process influent and the concentration of suspended solids significantly exceed the specified parameters in February and May. At volley of sewage on wastewater treatment plants in March, the concentration of BOD5 is more than 600 mg l-1. It is shown that overestimated indicators of wastewater pollution at the entrance in the spring period significantly reduce the effectiveness of biological removal of nitrogen and phosphorus compounds.

Use of waste marble powder for the synthesis of novel calcium-rich biochar: Characterization and application for phosphorus recovery in continuous stirring tank reactors

This study investigates—for the first time—the synthesis of a novel Ca-rich biochar (N–Ca–B) and its potential use for phosphorus (P) recovery from both synthetic solutions (SS) and treated urban wastewater (TUW) in a continuous stirring tank reactor (CSTR) mode. The novel biochar was synthesized by pyrolysis at 900 °C of a mixture composed of three different materials: animal biomass (poultry manure; PM), lignocellulosic waste (date palm fronds; DPFs), and abundant mineral waste (waste marble powder; WMP). Characterization of N–Ca–B showed that it has good textural properties: well-developed porosity, and high specific surface area. Furthermore, high calcium hydroxide (Ca(OH)2) and calcium oxides (CaO) nanoparticle loads were observed on the biochar surface. The dynamic CSTR assays indicated that the P recovery efficiency mainly depended on the biochar mass, P influent concentration, and, especially, the Ca content of the feeding solution. Owing to its richness in Ca cations, TUW exhibited the highest adsorbed P amount (109.2 mg g−1), i.e., about 14% larger than the SS. P recovery occurs through precipitation as hydroxyapatite, surface complexation, and electrostatic interactions with positively charged biochar particles. In real-world scenarios, CSTR systems can be applied as a tertiary treatment step in existing wastewater treatment plants (WWTPs). Decanted P-loaded biochar can be used in agriculture as a slow-release fertilizer instead of commercial products.

Suppression of nitrite oxidizing bacteria by hydrogen peroxide for energy reduction in municipal wastewater treatment

This paper investigated the application of hydrogen peroxide (H2O2) for achieving partial nitrification in mainstream municipal wastewater treatment process. The investigation was carried out in both bench-scale and pilot-scale sequencing batch reactor systems using primary effluent as feed from municipal wastewater treatment plant. H2O2 played a dual role of: (1) inhibitor for nitrifying microorganisms, and (2) supplemental oxygen source. Bench scale studies were carried out at various doses of initial hydrogen peroxide concentrations (10,25,50,100 mg/L). It was found that at a concentration of 50 mg/L and above ammonia removal reduced by more than 80% implying significant impact on both ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB). After an acclimatization period of 18 days at a dose of 50 mg/L H2O2, complete nitrification was observed with about 30% nitrite accumulation in the effluent which showed NOBs were impacted more significantly than AOBs. It was also observed from the long-term pilot-scale study that the inhibitory impact on NOBs is almost double the impact of on AOBs which facilitated partial nitrification resulting a nitrite accumulation ratio up to 60% in the effluent at 2 mg/L DO and 15 days SRT.Peroxide dosing resulted in an energy savings of 12–15% compared to a control reactor. It was also shown that by reducing the DO from 2 to 1 mg/L, additional power saving of 15% is achievable. Therefore, the proposed approach is an efficient method for aeration energy savings and can be easily implemented in existing wastewater treatment plants.

Integrated Treatment of Per- and Polyfluoroalkyl Substances in Existing Wastewater Treatment Plants-Scoping the Potential of Foam Partitioning.

Foam fractionation is becoming increasingly popular as a treatment technology for water contaminated with per- and polyfluoroalkyl substances (PFAS). At many existing wastewater treatment facilities, particularly in aerated treatment steps, foam formation is frequently observed. This study aimed to investigate if foam fractionation for the removal of PFAS could be integrated with such existing treatment processes. Influent, effluent, water under the foam, and foam were sampled from ten different wastewater treatment facilities where foam formation was observed. These samples were analyzed for the concentration of 29 PFAS, also after the total oxidizable precursor (TOP) assay. Enrichment factors were defined as the PFAS concentration in the foam divided by the PFAS concentration in the influent. Although foam partitioning did not lead to decreased ∑PFAS concentrations from influent to effluent in any of the plants, certain long-chain PFAS were removed with efficiencies up to 76%. Moreover, ∑PFAS enrichment factors in the foam ranged up to 105, and enrichment factors of individual PFAS ranged even up to 106. Moving bed biofilm reactors (MBBRs) were more effective at enriching PFAS in the foam than activated sludge processes. Altogether, these high enrichment factors demonstrate that foam partitioning in existing wastewater treatment plants is a promising option for integrated removal. Promoting foam formation and removing foam from the water surface with skimming devices may improve the removal efficiencies further. These findings have important implications for PFAS removal and sampling strategies at wastewater treatment plants.

Selection of Wastewater Treatment Technology: AHP Method in Multi-Criteria Decision Making

Wastewater treatment is a process that reduces pollution to those quantities and concentrations at which purified wastewater is no longer a threat to human and animal health and safety and does not cause unwanted changes in the environment. Municipal wastewater is classified as biodegradable water. Special importance should be given to wastewater with a high content of organic matter (COD), phosphorus (P) and nitrogen (N). MBBR technology, developed on the basis of the conventional activated sludge process and the bio filter process, does not take up much space and does not have problems with activated sludge, as in the case of conventional biological reactors, and has shown good results for the removal of organic matter, phosphorus and nitrogen. The aim of this paper is to optimize the wastewater treatment process in the municipality of Dojran, North Macedonia. Three alternative solutions for improving the capacity for wastewater treatment in the municipality of Dojran were analyzed. The shortlist of variants was made on the basis of several criteria, including: analysis of the system in the tourist season and beyond, assessment of the condition and efficiency of the existing wastewater treatment plant (WWTP) in combination with a new treatment plant, treatment efficiency when using different wastewater treatment technologies, the size of the site needed to accommodate the capacity, as well as the financial parameters for the proposed system. The selection of the most favorable solution for the improvement of the wastewater treatment system was made using the AHP (analytic hierarchy process) method. In order to select the optimal solution, a detailed analysis was conducted, considering several decision-making criteria, namely the initial investment, operating costs and management complexity. Based on the obtained results, Variant 3 was recommended, that is, the construction of a completely new station with MBBR technology, with a capacity for 6000 equivalent inhabitants.

Efficient H2O2 production from urine treatment based on a self-biased WO3/TiO2-Si PVC photoanode and a WO3/CMK-3 cathode

Urine accounts for only 1% of municipal wastewater volume but contributes 80% of nitrogen, which has become one of the challenges for existing wastewater treatment plants. Herein, we proposed a novel approach based on a self-biased WO3/TiO2-Si PVC photoanode and a WO3-modified mesoporous carbon (CMK-3) cathode (WO3/CMK-3) to produce significantly high-value chemical H2O2 from urine treatment with effective total nitrogen removal. The central idea of the design is to achieve a feasible reversal of the thermodynamic trend of O2 reduction to H2O2 from a non-spontaneous to a strongly spontaneous process by combining it with a urine treatment reaction that releases large amounts of chemical energy in the photoelectrocatalytic (PEC) system. The results indicated that the H2O2 production was boosted remarkably by urine disposal reaction (5.13 mg cm−2 h−1) with a faradaic efficiency of 72%, and the WO3/CMK-3 cathode showed 6.1 and 2.5 times higher H2O2 production activity than the common gas diffusion electrode and carbon felt electrode, respectively. Moreover, urine was degraded effectively into N2 with a total nitrogen removal of 91.4% within 120 min, and the kinetic constant of urine degradation was 0.0397 min−1, which was 15.4 times that of the blank. The results of ESR and quenching experiments demonstrated that the amine group of urine selectively and rapidly converted into N2 by Cl•. This study provides new insights into efficient urine disposal and synchronous H2O2 production.

THE PROBLEMS AND PROSPECTS OF UTILIZATION OF SEWAGE SLUDGE AND RECLAMATION OF DISTURBED LANDS IN THE NORTH-WEST OF RUSSIA AND WAYS TO SOLVE THEM JOINTLY

This review article raises the related issue of disturbed land reclamation and sewage sludge disposal. One of the components of disturbed land reclamation is considered - the problem of obtaining the most accessible and cheap fertile soil layer in sufficient quantity, options are listed: natural humus horizon; substrates based on peat of varying degrees of decomposition, based on wood waste from logging and woodworking, based on composts (leaf litter, agricultural waste, other). The main emphasis is placed on substrates based on municipal sewage sludge and pulp and paper mill waste, on the basis of which, during processing, organo-mineral compositions can be obtained with their further use as fertile soil layer. Gaps are noted in the modern regulatory framework, especially in relation to the use of sewage sludge as a fertile soil layer for the reclamation of disturbed land, including on forest fund lands. As an example, the situation with the use and disposal of sewage sludge in the Northwestern Federal District was considered based on data on the volume of waste production at existing wastewater treatment plants. Three categories of sewage sludge are distinguished by composition and two main methods of disposal currently used (incineration and removal to municipal service waste landfills). Separately, attention is focused on the situation with the accumulation of sewage sludge at wastewater treatment plants in settlements, including those with a pulp and paper mill as a city-forming enterprise. In conclusion, conclusions are drawn about the need to improve the existing regulatory framework in terms of the use of sewage sludge for the purposes of reclamation, about the priority of developing organo-mineral compositions that meet the tasks of reclamation, giving them an official status, and about the advisability of developing a strategic state document aimed at regulating the issues of reclamation of disturbed lands: the relevance of which is confirmed by the annual increasing areas, passing into the category of disturbed land.