Population Equivalents Research Articles

Universal health coverage in China: a serial national cross-sectional study of surveys from 2003 to 2018

Achieving universal health coverage (UHC) is one crucial target of the Sustainable Development Goals. However, consistent trends data for UHC evaluation in China are still scarce. The aim of our study was to provide a comprehensive assessment of UHC in China. In this serial cross-sectional study, we collected nationally representative data from the latest four rounds (2003, 2008, 2013, and 2018) of the National Health Service Surveys, with the aim of evaluating UHC in China. These surveys used multistage stratified cluster sampling covering all 31 provinces, autonomous regions, and municipalities in mainland China. Within each household, all members aged 15 years and older were interviewed. For children and adolescents aged younger than 15 years, their adult family members answered the questions for them. We constructed a UHC index following the WHO-recommended framework that included service coverage (nine prevention indicators and five treatment indicators) and financial protection (three indicators) dimensions. Bayesian regression models were done to investigate the trends in and projections of UHC index and indicators, with average annual percentage change (AAPC) and probabilities of achieving the 2030 WHO targets. Based on trends and projections, we counted population equivalents with UHC coverage. To examine the potential efficiency of financial investment, we quantified UHC performance based on government health expenditure (GHE) per capita. Finally, we explored the association between each UHC indicator and macroeconomic and health systems characteristics by using multiple regression. We sampled 57 023 households from 95 counties between September and October, 2003; 56 456 households from 94 counties between June and July, 2008; 93 613 households from 156 counties between August and October, 2013; and 94 076 households from 156 counties in September, 2018. A total of 901 182 individuals were involved in this study (193 689 in 2003, 177 501 in 2008, 273 688 in 2013, and 256 304 in 2018). Although the overall UHC increased from 44·0% (95% CI 43·0-44·9) in 2003 to 79·8% (79·2-80·3) in 2018 and is predicted to meet the 80% global target by 2030, the progress towards UHC has steadily slowed down nationally. Based on current projections, an estimated 105·8 (95% CI 27·3-189·1) million population equivalents would still not have UHC coverage in 2030. The treatment index showed a large increase over time from 2003 to 2018 (AAPC 4·9%, 2·9-7·2), with minimal disparities and all subgroups will achieve the target in the treatment domain by 2030 (possibilities higher than 90%). However, the prevention index presented poor performance with a small increase over time from 2003 to 2018 (AAPC 1·4%, 0·3-2·5) and sizable disparities across regions, urban-rural areas, and income (all p<0·0001). To achieve at least 80% UHC coverage, provinces would need to reach at least ¥445 in GHE per capita per year under maximum efficiency. However, large gaps between the observed and frontier UHC index, especially in several western provinces, indicated inefficiency. Furthermore, we found that primary health-care institutions were closely and positively related to UHC indicators especially in the prevention domain. Although considerable achievements have been made, the progress towards UHC is not keeping pace with the rapid society development in China. Considering an increased burden in non-communicable diseases and an ageing population, prioritising the efficacy of financial investment and optimising resource allocation by strengthening primary health care are necessary to achieve UHC in China. National Natural Science Foundation of China and National Health Commission of the People's Republic of China.

Specification and Classification of Pelletised Dried Sewage Sludge: Identifying Its Key Properties as a Renewable Material for Enabling Environmentally Non-Harmful Energy Utilisation

Renewable active sludge is a smart material for wastewater treatment and the protection of surface water bodies. The generated pellets (dried and pelletised dehydrated anaerobically stabilised excess sludge) are produced in a quantity of 31.4 ± 5.6 g dry matter (DM) per one Population equivalent (PE) calculated to COD (PECOD) in one day. As pellets are combustible material, their energy utilisation must reach the sustainable development goals (SDGs)—a bridge must be created between “treated sewage sludge as the tool to remove pollutants and nutrients from wastewater” and “preparation of the valuable material as a solid recovered fuel (SRF) that meets customer-specific requirements”. Technical Report CEN/TR 15508 and Technical Standard EN ISO 21640 set up methods for specifying and classifying pellets as an SRF. In the last eleven years (2010–2021), pellets’ net calorific value (NCV) is 13.0 ± 0.7 MJ kg−1 as received (ar). In 2021, the 80th percentile of the Hg/NCV ratio was 0.079 mg Hg MJ−1. In 2010–2021, the annual amount of Hg transferred to stakeholders reduced by 64.3% m/m—from 10.1 kg to 3.67 kg. The halogen contents of the pellets do not threaten corrosion to the incineration facility. Stable pellets’ energy potential and perspective ash composition for critical raw materials recovery qualify pellets as a specific waste stream and a renewable material for SRF production.

Avaliação de desempenho de uma estação de tratamento de esgoto movida a energia solar (SBR de dois estágios) operada em regiões de clima tropical

ABSTRACT This article investigates the performance behaviour of a small decentralized wastewater treatment plant with a capacity of up to 50 population equivalents powered by solar energy. The two-stage sequencing batch reactor (SBR) consists of a photovoltaic (PV) system to deliver energy, a battery storage for night operation and two reactor tanks. In the experimental period of 157 days, the wastewater inflow was increased from 3 to 4.5 and 6 m3.d−1, with sludge ages of 32 ± 2 d in the beginning and 21 ± 2 d in the end. The results corresponding to the different phases indicated high efficiency and stability of the system with domestic wastewater, reaching efficiencies of the test periods of 93 ± 2%, 86 ± 4% and 93 ± 6% for removal of chemical oxygen demand, nitrogen and phosphorus, respectively. In the last 51 days, aeration in the night was interrupted for three hours to save energy and study the behaviour of extended non-aerated phases. A shortening of the aeration phases can help to extend the lifetime of batteries and reduce operational costs, while limiting values in the outlet are still met.

How Many Small Agglomerations Do Exist in the European Union, and How Should We Treat Their Wastewater?

The European Union (EU)’s legislation on urban wastewater requires all agglomerations with a population equivalent (PE) above 2000 people to undergo a secondary (mechanical/physical and biological) wastewater treatment. Agglomerations below 2000 PE, though, fall outside the scope of the current EU’s legislation. As such, their regulation is heterogeneous across the various EU member states, and there is no systematic collection nor reporting of data enabling an estimation of their actual significance as a source of pollution for the receiving water bodies. Here we present a spatial model to delineate agglomerations in a GIS, based on population distribution and land cover. From the model results, in the EU, we identify 364,650 agglomerations with 2000 PE or less, housing a cumulative population of about 75 million inhabitants. We then calculate the organic matter and nutrient loads these agglomerations can discharge, assuming they presently undergo primary wastewater treatment, and the reduction of loads that can be expected under different treatment scenarios, together with the corresponding treatment costs based on a simple cost model. Using a conventional shadow price for the organic matter and nutrients removed, we show that all treatment scenarios show a benefit-to-cost ratio (B/C) above (or close to) 1. However, only a scenario of secondary treatment applied to all agglomerations above 1000 PE provides sufficient safety margins on the B/C. This suggests the opportunity to expand the scope of the current legislation down to agglomerations of this size, while addressing smaller agglomerations depending on their actual impacts on the receiving water bodies, through “appropriate treatments” defined by the local authorities.

Plant-wide modeling of a metropolitan wastewater treatment plant to reduce energy consumption and carbon footprint.

A real metropolitan wastewater treatment plant (RWWTP) serving a population equivalent of 1.55 million was modeled to reduce energy consumption and carbon footprint (CFP). An approach was proposed to handle the dilution factor and partial aeration due to discontinuous air diffuser locations in the Bardenpho-5 configuration. Various operational, structural, and configurational modifications were evaluated. Results indicated that management scenarios might provide conflicting outcomes for different targets. Reduced energy consumption may not result in lower CFP at the same time. Moreover, operational changes that would impact total nitrogen (TN) concentrations and N2O release may significantly impact CFP. A policy of using a modified Bardenpho-5 process with reduced internal recycle (IR) ratio, waste activated sludge (WAS), and return activated sludge (RAS) flow rates provided the lowest CPF. Modified Bardenpho-5 process and replacing belt thickeners with gravity thickeners supplied the highest savings in energy consumption. Overall, up to 14% and 20% reductions were possible in the energy consumption and CFP of the plant, respectively. The RWWTP may save up to 10% in energy expenses annually by operational modifications.

Treatment of micropollutants in wastewater: Balancing effectiveness, costs and implications

In this contribution, we analyse scenarios of advanced wastewater treatment for the removal of micropollutants. By this we refer to current mainstream, broad spectrum processes including ozonation and sorption onto activated carbon. We argue that advanced treatment requires properly implemented tertiary (nutrient removal) treatment in order to be effective. We review the critical aspects of the main advanced treatment options, their advantages and disadvantages. We propose a quantification of the costs of implementing advanced treatment, as well as upgrading plants from secondary to tertiary treatment when needed, and we illustrate what drives the costs of advanced treatment for a set of standard configurations. We propose a cost function to represent the total costs (investment, operation and maintenance) of advanced treatment. We quantify the implications of advanced treatment in terms of greenhouse gas emissions. Based on the indicators of total toxic discharge, toxicity at the discharge points and toxicity across the stream network discussed in Pistocchi et al. (2022), we compare costs and effectiveness of different scenarios of advanced treatment. In principle the total toxic load and toxicity at the points of discharge could be reduced by about 75 % if advanced treatment processes were implemented virtually at all wastewater treatment plants, but this would entail costs of about 4 billion euro/year for the European Union as a whole. We consider a “compromise” scenario where advanced treatment is required at plants of 100 thousand population equivalents (PE) or larger, or at plants between 10 and 100 thousand PE if the dilution ratio at the discharge point is 10 or less. Under this scenario, the length of the stream network exposed to high toxicity would not increase significantly compared to the previous scenario, and the other indicators would not deteriorate significantly, while the costs would remain at about 1.5 billion Euro/year. Arguably, costs could be further reduced, without a worsening of water quality, if we replace a local risk assessment to generic criteria of plant capacity and dilution in order to determine if a WWTP requires advanced treatment.

Evaluating the Performance of Small Wastewater Treatment Plants

An evaluation of the treatment performance of small wastewater treatment plants with the capacity of ≤50 PE (population equivalent) was carried out using data collected in external monitoring reports, taking Upper Austria as an example. External monitoring data for 2009–2018 were available for this analysis. About 2′500 small WWTPs are in operation in Upper Austria. The main technologies implemented include about 870 Sequencing Batch Reactor (SBR) plants, 630 conventional activated sludge (CAS) plants and 535 vertical flow (VF) wetlands. The data set for the present evaluation comprises a total of approx. 14′000 external monitoring reports from approx. 2′000 small WWTPs. This paper presents the results of this evaluation. The evaluation showed that all technologies meet the legal requirements regarding BOD5, COD and NH4-N effluent concentrations. However, for small WWTPs with a polishing stage consisting of a VF wetland, the median values of the effluent concentrations and the limit value exceedances are significantly lower. There is no evidence of a significant deterioration in treatment performance with the age of the plant for any technology. However, for all technical WWTPs such as SBR and CAS plants, a greater fluctuation of the measured values (i.e. the median values of the effluent concentrations) can be observed when the plant is longer in operation. Compared to technical WWTPs, this fluctuation is significantly smaller in VF wetlands.

SAMPLE EQUALITY TEST IN BLENDED LEARNING USING GOOGLE CLASSROOM

Along with the recovery from the COVID-19 pandemic, the government expects the use of technology, information and communication (ICT) in innovative learning activities in schools. One of them is in the process of Limited Face to Face Learning (PTMT) mathematics in Vocational High Schools (SMK) to provide more opportunities for students to actively participate in each stage of learning. The quality of education is very dependent on the quality of learning carried out by teachers in the classroom. Optimization of the learning process can be done by integrating the use of technology as a learning medium, one of which is by using Google Classroom in blended learning at school. o find out the equality between classes in the population, a t-test was conducted. The results of the population equivalence test obtained that all students of Class XI SMK Wira Harapan for the academic year 2022/2023 were equal and the experimental group selected was X JB1 and the control group obtained X AP.

European scale assessment of the potential of ozonation and activated carbon treatment to reduce micropollutant emissions with wastewater

Micropollutants (MPs) in wastewater pose a growing concern for their potential adverse effects on the receiving aquatic environment, and some countries have started requiring that wastewater treatment plants remove them to a certain extent. Broad spectrum advanced treatment processes, such as ozonation, activated carbon or their combination, are expected to yield a significant reduction in the toxicity of effluents. Here we quantify the reduction of effluent toxicity potentially achieved by implementing these advanced treatment solutions in a selection of European wastewater treatment plants. To this end, we refer to a list of “total pollution proxy substances” (TPPS) composed of 1337 chemicals commonly found in wastewater effluents according to a compilation of datasets of measured concentrations. We consider these substances as an approximation of the “chemical universe” impinging on the European wastewater system. We evaluate the fate of the TPPS in conventional and advanced treatment plants using a compilation of experimental physicochemical properties that describe their sorption, volatilization and biodegradation during activated sludge treatment, as well as known removal efficiency in ozonation and activated carbon treatment, while filling the gaps through in silico prediction models.We estimate that the discharge of micropollutants with wastewater effluents in the European Union has a cumulative MP toxicity to the environment equal to the discharge of untreated wastewater of ca. 160 million population equivalents (PE), i.e. about 30 % of the generated wastewater in the EU. If all plants above a capacity of 100,000 PE were equipped with advanced treatment, we show that this load would be reduced to about 95 million PE. In addition, implementing advanced treatment in wastewater plants above 10,000 PE discharging to water bodies with an average dilution ratio smaller than 10 would yield a widespread improvement in terms of exposure of freshwater ecosystems to micropollutants, almost halving the part of the stream network exposed to the highest toxic risks.Our analysis provides background for a cost-effectiveness appraisal of advanced treatment “at the end of the pipe”, which could lead to optimized interventions. This should not be regarded as a stand-alone solution, but as a complement to policies for the control of emissions at the source for the most problematic MPs.

An Evidence-Based Survey on Full-Scale Membrane Biological Reactors: Main Technical Features and Operational Aspects

This paper presents the results of a survey on full-scale membrane biological reactors (MBRs) wastewater treatment plants (WWTPs) in Italy. Alongside the main technical characteristics of the Italian MBR plants, the opinions of the plant managers on the operational advantages and disadvantages are described. As reported by the MBR technology suppliers, approximately 290 MBR municipal or industrial WWTPs are in operation in Italy, out of which 242 were studied in this survey. Data from more than one hundred municipal WWTPs were collected; these account for a total capacity of about 2,000,000 population equivalent (PE), which corresponds to 3% of the total organic load treated by the Italian WWTPs with secondary and advanced treatment. Usually, small installations adopt the flat-sheet rather than hollow-fiber membrane configuration. The main reasons why the MBR technology has been preferred to other options are its potential to be used for increasing the treatment capacity of existing plants and its compactness. Moreover, the followed operational advantages have been highlighted: easiness to comply with the discharge limits, removal of pathogens without specific disinfection units, possibility of internal reuse of the effluent, and process automation. Membrane fouling and plant shutdown have been recorded as the most relevant troubles, the last one indeed occurring only occasionally or rarely.

Situation Analysis and the Potential for Circularity of the Wastewater Sector in Lithuania

The concept of circular economy is one of the priority areas for economic development on which the current environmental policy of the European Union is based. Most existing European wastewater treatment plants were built and operated according to the concept of linear economy where wastewater and sewage sludge were considered as waste only. In fact, there is a wide range of possibilities to use them as a resource to recover materials and energy. Implementation of the concept of circular economy in a relatively small country requires a great deal of additional research and monitoring to assess the available potential. In this paper, data on municipal wastewater in agglomerations larger than population equivalent of 2000 were analyzed, and the situation is presented through indicators covering prevention, removal, reuse, recycling, and recovery. The novelty of this article is that it evaluates the circularity of Lithuanian wastewater treatment plants and their potential for the future. Thus far, the wastewater sector in the country has been found to largely comply with legal obligations, but very few solutions of circularity were found to be implemented.

Description of a Fe/Al Electrocoagulation Method Powered by a Photovoltaic System, for the (Pre-)Treatment of Municipal Wastewater of a Small Community in Northern Greece

Small and insular communities are sometimes not served by an efficient Wastewater Treatment Plant, and this is a hazard for both the environment and public health. A wastewater treatment apparatus based on the electrocoagulation process (EC) was tested with municipal wastewater from a small community in Northern Greece with a maximum of 6500 population equivalents. COD decrease was assessed under various parameters: current intensity, time duration, pH and use of Fe or Al electrodes. A simulation of meeting the community’s electricity needs with this apparatus was tested through RETScreen software. The results showed a satisfactory COD decrease through electrocoagulation which was affected by all the parameters mentioned; Fe electrodes could efficiently be used at 300 mA for 60 min for 55% COD removal. It was also shown that a photovoltaic panel system covers the electricity needs of the apparatus, thus no external electricity source is needed for its use. This apparatus could be used effectively by this community, so that the running costs are minimal.

Microplastics removal from a primary settler tank in a wastewater treatment plant and estimations of contamination onto European agricultural land via sewage sludge recycling

Wastewater treatment plants (WwTPs) remove microplastics (MPs) from municipal sewage flow, with the resulting bulk of MPs being concentrated within generated sewage sludge which is frequently recycled back onto agricultural land as accepted practice in many European countries as a sustainable fertiliser resource. This circular process means that MPs successfully removed from WwTPs are deposited into the soil and able to return into the natural watercourse by means of run-off or infiltration to groundwater. This study quantifies the removal efficiency of MPs with size ranging between 1000 and 5000 μm in a primary settlement tank (PST) at a WwTP serving a population equivalent of 300,000 and provides MP concentrations in the generated sewage sludge. Our study revealed that the proportion of MPs partitioning in a PST to settled sludge, floating scum and effluent was 96%, 4% and 0% respectively, implying 100% removal of MPs of 1000–5000 μm in size. The generated sewage sludge was estimated to contain concentrations of approximately 0.01 g of MPs or 24.7 MP particles per g of dry sewage sludge solid, equivalent to ∼1% of the sewage sludge weight. Using these figures and data from the European Commission and Eurostat, the potential yearly MP contamination onto soils throughout European nations is estimated to be equivalent to a mass of MPs ranging between 31,000 and 42,000 tonnes (considering MPs 1000–5000 μm in size) or 8.6×1013–7.1×1014 MP particles (considering MPs 25–5000 μm in size). An estimated maximum application rate of 4.8 g of MP/m2/yr or 11,489 MP particles/m2/yr, suggests that the practice of spreading sludge on agricultural land could potentially make them one of the largest global reservoirs of MP pollution. Hence, recycling raw sewage sludge onto agricultural soils should be reviewed to avoid introducing extreme MP pollution into the environment.

Municipal Wastewaters Carry Important Carbapenemase Genes Independent of Hospital Input and Can Mirror Clinical Resistance Patterns.

ABSTRACTThe spatiotemporal variation of several carbapenemase-encoding genes (CRGs) was investigated in the influent and effluent of municipal WWTPs, with or without hospital sewage input. Correlations among gene abundances, bacterial community composition, and wastewater quality parameters were tested to identify possible predictors of CRGs presence. Also, the possible role of wastewaters in mirroring clinical resistance is discussed. The taxonomic groups and gene abundances showed an even distribution among wastewater types, meaning that hospital sewage does not influence the microbial diversity and the CRG pool. The bacterial community was composed mainly of Proteobacteria, Firmicutes, Actinobacteria, Patescibacteria, and Bacteroidetes. Acinetobacter spp. was the most abundant group and had the majority of operational taxonomic units (OTUs) positively correlated with CRGs. This agrees with recent reports on clinical data. The influent samples were dominated by blaKPC, as opposed to effluent, where blaIMP was dominant. Also, blaIMP was the most frequent CRG family observed to correlate with bacterial taxa, especially with the Mycobacterium genus in effluent samples. Bacterial load, blaNDM, blaKPC, and blaOXA-48 abundances were positively correlated with BOD5, TSS, HEM, Cr, Cu, and Fe concentrations in wastewaters. When influent gene abundance values were converted into population equivalent (PE) data, the highest copies/1 PE were identified for blaKPC and blaOXA-48, agreeing with previous studies regarding clinical isolates. Both hospital and non-hospital-type samples followed a similar temporal trend of CRG incidence, but with differences among gene groups. Colder seasons favored the presence of blaNDM, blaKPC and blaOXA-48, whereas warmer temperatures show increased PE values for blaVIM and blaIMP.IMPORTANCE Wastewater-based epidemiology has recently been recognized as a valuable, cost-effective tool for antimicrobial resistance surveillance. It can help gain insights into the characteristics and distribution of antibiotic resistance elements at a local, national, and even global scale. In this study, we investigated the possible use of municipal wastewaters in the surveillance of clinically relevant carbapenemase-encoding genes (CRGs), seen as critical antibiotic resistance determinants. In this matter, our results highlight positive correlations among CRGs, microbial diversity, and wastewater physical and chemical parameters. Identified predictors can provide valuable data regarding the level of raw and treated wastewater contamination with these important antibiotic resistance genes. Also, wastewater-based gene abundances were used for the first time to observe possible spatiotemporal trends of CRGs incidence in the general population. Therefore, possible hot spots of carbapenem resistance could be easily identified at the community level, surpassing the limitations of health care-associated settings.

Potentials and Integrated Suitability Pre-assessment of Wastewater Treatment Plants as Local Energy Cells

In 2018 the European Union has recognized wastewater as a renewable energy source, particularly due to its thermal energy content. To create and further develop knowledge on the possible role that wastewater could play in the energy transition, this article pursues two objectives: 1) it presents an overview on the electric and thermal energy potentials available at the wastewater treatment plants (WWTPs) in the Central European area also taking their spatial context to adjacent settlement structures into account. 2) It introduces a small number of easy to apply criteria to (pre-)assess the suitability of WWTPs for being integrated into local energy (heat) supply concepts from an integrated perspective (considering energetic, spatial and environmental aspects). The investigations address the energy generation potentials of 3,315 WWTPs (with a treatment capacity of at least 5,000 population equivalents) in the area under survey. Analysis reveal, that notable amounts of heat ranging to almost 26 TWh/a are available. Their exploitation appears very promising, as investigations also show, that about 73% of the considered WWTPs are situated near or even within existing settlement structures implying very advantageous heat supply distances. Following the estimation of energy potentials, which is made available in the supplementary material, the presented suitability criteria can then be used to identify the most promising WWTPs in a specific regional/local context, in the investigated Central European area and beyond.

Opportunities for wastewater heat recovery in Hungary and its role in the circular economy

Most of the energy content of wastewater can be found in wastewater heat, however, its recovery is limited. In this article, the current situation, future opportunities of wastewater heat recovery are presented based on secondary data collection, mentioning the constraints and main influencing factors of sustainable implementation of heat recovery systems in Hungary. Besides, the already existing systems are described. As regards the capacities of treatment plants, 103 of the 574 domestic plants have a capacity of over 20,000 Population Equivalent (PE), of which 25 plants have a capacity of over 100,000 PE. According to our calculations, in big cities/capitals (20.000 – 100.000, and over 100.000 inhabitants), it may be possible to recover wastewater heat sustainably in several places. In small towns (5.000 – 20.000 inhabitants), wastewater heat recovery can be technologically and economically sustainable only in the presence of agricultural or industrial plants with high and continuous wastewater feed into the pipeline system. Taking into account the temperature conditions at each place of use and their estimated fluctuations, it can be said that proper, careful planning, sizing and implementation have a crucial effect on the efficiency of microbiological activity in the treatment plants. In bigger cities, of course, the effect of the temperature drop of one main collector may be minimal, however, in smaller and medium-sized settlements, excessive heat extraction may result in complete inhibition or cessation of nitrification. In Hungarian case studies, the maximum acceptable temperature drop is approx. 2-3 °C. It can be stated that energy recovery from wastewater may be very promising considering the size and temperature limitations. Therefore, the rational recovery of wastewater heat can be an important part of the implementation of circular economy and sustainable energy utilization in wastewater management, resulting in significant energy savings and pollutant reduction. JEL CODE: Q25

Energy Consumption and Carbon Footprint of Greek Wastewater Treatment Plants

Wastewater treatment plants (WWTPs) exhibit significant energy consumption and produce large amounts of Greenhouse Gas emissions (GHG emissions). Energy efficiency and reduction in GHG emissions in WWTPs have become important issues, especially in view of the climate crisis. The core objective of this work is to assess the energy and carbon footprint of Greek WWTPs and to propose methods to improve energy efficiency and reduce GHG emissions. Data were collected from 31 Greek WWTPs with an average treatment capacity between 250 and 3,650,000 population equivalents (PE). The total population served by the 31 WWTPs was over 6,000,000, which is more than half of the population in Greece with access to WWTPs. Based on the results, the annual average energy consumption for small, medium and large WWTPs equals 137 kWh/PE, 48 kWh/PE and 32 kWh/PE, respectively. Accordingly, annual average GHG emissions, both biogenic and non-biogenic in small, medium and large WWTPs are equal to 207 kgCO2e/PE, 144 kgCO2e/PE and 89 kgCO2e/PE, respectively. Annual average on-site GHG emissions are equal to 56.5 kgCO2e/PE, while the average off-site GHG emissions account for 16.9 kgCO2e/PE. Based on the results, acceptable and attainable targets for WWTPs energy consumption and GHG emissions are proposed.

Using the inverse dispersion method to determine methane emissions from biogas plants and wastewater treatment plants with complex source configurations

Wastewater treatment plants (WWTPs) and biogas plants (BGPs) are significant sources of methane (CH4), with a combined share of around 40% within the waste sector of the Swiss national emission inventory. We conducted whole-plant CH4 emission measurements at two WWTPs and four agricultural BGPs in Switzerland using the inverse dispersion method (IDM). This involved open-path concentration measurements up- and downwind of the plant in combination with a backward Lagrangian stochastic (bLS) model. WWTPs in particular consist of multiple CH4 sources with different areas and emission strengths. For the combination of the individual emission sources in the bLS modelling, three different calculation approaches with different levels of detail were applied: (i) single source over enveloping polygon area, (ii) uniform emission density for all individual source areas, (iii) specified relative weighting of individual sources based on literature data. Average CH4 emissions for WWTP-1 and WWTP-2 were 0.82 kg h−1 and 0.61 kg h−1 and scaled to population equivalents (PE) 166 g PE−1 y−1 and 381 g PE−1 y−1, respectively. BGPs CH4 emissions varied between 0.39 kg h−1 and 2.22 kg h−1, corresponding to less than 5% of the plants’ CH4 production. The highest numbers were due to measurements during other than normal operating conditions. The emissions of WWTPs and BGPs comply with literature values. Approach (iii) with source weighting led to a difference of up to 43% for the two WWTPs compared to the assumption of uniform emissions. Furthermore, we demonstrate how multiple open-path concentration measurements can be combined and how the measurements can be corrected for nearby external CH4 sources not belonging to the investigated plants. The results of the present study contribute to improved emission data from the waste sector.

Future nutrient recovery from sewage sludge regarding three different scenarios - German case study

Agricultural sewage sludge utilization becomes less important in Germany. In 2017, new fertilizer and waste laws caused the agricultural sewage sludge utilization to collapse by more than a quarter. From 2029, German wastewater treatment plants (WWTPs) must recover phosphorus (P) from sewage sludge if it contains more than 2 wt % P. Agricultural utilization will be prohibited for large WWTPs >100,000 population equivalents (pe) from 2029 and > 50,000 pe from 2032. In Germany, each federal state must annually report amounts and quality of agriculturally utilized sewage sludge which was 16% of the total disposal in 2019. The reports of 10 states were evaluated for 2016 and 2017 representing approx. 60% of the total agriculturally used sludge volume. In 2016, 60% of the WWTPs’ sludges exceeded the recovery limit of 2 wt % P which is 70% of the amount of sludge and 85% of the phosphorus load. Other nutrients are not affected by the recovery obligation. However, many P recovery processes recover other nutrients, too. Considering three different scenarios for future German sewage sludge disposal shows that 70–77% of the P load in sewage sludge will probably be recovered in the future. At the same time, this applies for about 0–16% nitrogen, 36–52% of calcium, 31–53% of potassium, and 40–52% of magnesium. However, these recovered nutrients loads can substitute only 1% or less of the commercial fertilizer demand except from phosphorus which is up to 43% of the demand.

Digesters as Heat Storage – Energetic Assessment of Flexible Variation of Digester Temperature

AbstractA flexible digester temperature enables holistic storage of surplus heat and minimization of heat deficits on water resource recovery facilities (WRRFs). Heat‐saving potentials, performance as heat storage, and emissions of CO2 are considered in four scenarios with increasing flexibility of digester temperature for a model WRRF with 500 000 PE (population equivalent). In comparison to a digester temperature at 37 °C all year, the scenario with seasonal variation of average digester temperatures between 32.5 and 43.6 °C has the greatest annual heat‐saving potential and increase of stored heat. Further, the ranges of digester temperatures indicate a great performance as heat storage.