Sewage Concentration Research Articles

Evaluation of Groundwater Infiltration in Sewer Networks Using Fluorescence Spectroscopy

Diagnosing water infiltration is imperative to assess the integrity and operation performance of sewer networks, which is challenging and costly due to the complex nature of these networks. This study proposes a simple approach to evaluate the extent of groundwater infiltration via a fluorescence spectroscopy method, i.e., the identification and quantification of the fluorescent signature components of the dissolved organic matter sewage. A newly built sewer network in Shantou, Southern China, was selected for the case study, and a mass balance method based on water quality characteristic factors (total phosphorus and NH4+-N) was applied in parallel for comparison. The results showed that the mass balance method was substantially influenced by fluctuations in sewage and external water concentrations, rendering it unreliable due to the extensive data and calculations required. Conversely, three-dimensional excitation–emission matrix–parallel factor analysis enabled the identification of terrestrial humus compounds as the signatures of underground water sources. The estimation indicates that the groundwater proportion across the four surveyed inspection wells along the pipeline network ranged from 10.8 ± 2.5% to 9.6 ± 3.5%, conforming to the allowable groundwater infiltration limits set for municipal sewage pipelines (10–15%). This study presents a simple method for the in-depth analysis of groundwater infiltration in urban sewage networks, providing valuable insights into maintaining water quality and network integrity.

Detection of BK and JC polyomaviruses in sewage water of the urban areas of Lahore, Pakistan.

The surveillance of sewage water has become an extremely essential tool to trace the circulation of viruses in a population and to predict the outbreak of viral diseases. Sewage monitoring is important for those viruses which cause subclinical infections since it is difficult to determine their prevalence. Polyomaviruses are ubiquitously present, circular double-stranded DNA viruses that can infect humans as well. Among all human polyomaviruses, BK polyomavirus and JC polyomavirus associated with the development of aggressive diseases in immunocompromised individuals, are highly prevalent. This study aimed to investigate the presence and the quantitative prevalence of these two disease-associated human polyomaviruses in sewage water collected from six drains of Lahore, Pakistan. The viruses present in the environmental samples were concentrated by PEG method before isolating viral nucleic acids. Conventional PCR amplifications were performed for molecular detection of BK polyomavirus and JC polyomavirus targeting their large tumor antigen genetic region. The presence of BK polyomavirus and JC polyomavirus was confirmed in the DNA extracted from concentrated sewage samples of each drain by performing both qualitative and quantitative PCR. Our data shows that the viral load ranged from 1278 to 178368 copies per µg of environmental DNA for BK polyomavirus and 5173 to 79129 copies per µg of environmental DNA for JC polyomavirus. In conclusion, here we report first time the detection of BK polyomavirus and JC polyomavirus in sewage water collected from six main drains in urban areas of Lahore, Pakistan showing the high prevalence ofthese viruses in the Pakistani population. This assay could be used as a proxy to determine the prevalence of these viruses in the Pakistani population.

Removal efficacy of fly ash composite filler on tailwater nitrogen and phosphorus and its application in constructed wetlands.

Constructed wetlands (CWs) have been widely used in tailwater treatment. However, it is difficult to achieve considerable removal efficiency of nitrogen and phosphorus in tailwater solely by CWs-an efficient green wetland filler is also important. This study investigated 160 domestic sewage treatment facilities (DSTFs) in rural areas from two urban areas in Jiaxing for TP and NH3-N and found that TP and NH3-N concentrations in rural domestic sewage (RDS) in this plain river network are still high. Therefore, we selected a new synthetic filler (FA-SFe) to enhance nitrogen and phosphorus reduction, and we discuss the importance of filler in constructed wetlands. Experiments revealed the adsorption capacity of the new filler: the maximum adsorption amounts of TP and NH3-N reached 0.47g m-2 d-1 and 0.91gm-2 d-1, respectively. The application potential of FA-SFe was verified in actual wastewater treatment, with the removal rates of ammonia nitrogen and TP reaching 71.3% and 62.7%, respectively. This study provides a promising pathway for nitrogen and phosphorus removal from rural tailwaters.

An Innovative Waterwheel-Rotating Biological Contactor (WRBC) System for Rural Sewage Treatment

The treatment of rural sewage has become an important part of environmental protection. In this study, a novel waterwheel-rotating biological contactor (WRBC) system, with intensified biofilm and high-shock load resistance, was applied to treat rural sewage. When the COD concentration of actual sewage fluctuated between 79–530 mg/L, the COD removal efficiency was 41.3–94.5%, and the NH4+-N removal efficiency always reach 100% with actual sewage. The TN removal efficiency changed between 14.3–86.2%, which was greatly affected by the water intake. The effluent TN concentration ranged from 5 to 14 mg/L, which meets the emission requirements. It maintained an absolute effluent stability when the change rates of influent loads (N or COD) varied from −60% to 100%. The biofilm morphology and the composition of extracellular polymeric substances were evaluated based on SEM and FTIR spectra. The results showed that the -NH2 group content increased compared with the inoculated sludge, and the biofilm formed more uneven compact clusters after the treatment of actual sewage. Based on 16SrRNA high-throughput sequencing techniques, the bacterial diversity and microbial community structure of the WRBC system over time was revealed. This study may help guide optimization strategies for more effective pollutant removal in rural areas.

Diffuse and concentrated nitrogen sewage pollution in island environments with differing treatment systems

Macroalgae is an under-utilised tool as a bioindicator of anthropogenic nitrogen loading to the coastal environment in the UK. This study compared two island systems—Jersey (Channel Islands) and St Mary’s (Isles of Scilly) to assess how differing sewerage infrastructure affects nitrogen loading. A total of 831 macroalgae samples of Fucus vesiculosus and Ulva sp. were analysed for nitrogen isotopes (δ15N). Elevated δ15N values were recorded for Jersey (> 9‰) in St Aubin’s Bay—caused by the outflow of the Bellozanne Sewerage Treatment Works (STW). δ15N isoplots maps indicate low diffusion of nitrogen out of St Aubin’s Bay. St Mary’s produced a varied δ15N isoplot map in comparison. δ15N was typically lower and is attributed to a smaller population and inefficient STW. Outflow of sewage/effluent at Morning Point, Hugh Town and Old Town produced elevated δ15N values in comparison to the island average. St Mary’s inefficient sewerage treatment and reliance on septic tanks/soakaways complicates δ15N interpretation although it still indicates that nitrogen pollution is an island-wide issue. Future sewerage development and upgrades on islands are required to prevent similar effluent environmental issues as recorded in St Aubin’s Bay. This study advocates the use of macroalgae as a bioindicator of nitrogen effluent in the marine environment.

Prediction of hospitalisations based on wastewater-based SARS-CoV-2 epidemiology

Wastewater-based epidemiology is widely applied in Austria since April 2020 to monitor the SARS-CoV-2 pandemic. With a steadily increasing number of monitored wastewater facilities, 123 plants covering roughly 70 % of the 9 million population were monitored as of August 2022. In this study, the SARS-CoV-2 viral concentrations in raw sewage were analysed to infer short-term hospitalisation occupancy. The temporal lead of wastewater-based epidemiological time series over hospitalisation occupancy levels facilitates the construction of forecast models. Data pre-processing techniques are presented, including the approach of comparing multiple decentralised wastewater signals with aggregated and centralised clinical data. Time‑lead quantification was performed using cross-correlation analysis and coefficient of determination optimisation approaches. Multivariate regression models were successfully applied to infer hospitalisation bed occupancy. The results show a predictive potential of viral loads in sewage towards Covid-19 hospitalisation occupancy, with an average lead time towards ICU and non-ICU bed occupancy between 14.8-17.7 days and 8.6–11.6 days, respectively. The presented procedure provides access to the trend and tipping point behaviour of pandemic dynamics and allows the prediction of short-term demand for public health services. The results showed an increase in forecast accuracy with an increase in the number of monitored wastewater treatment plants. Trained models are sensitive to changing variant types and require recalibration of model parameters, likely caused by immunity by vaccination and/or infection. The utilised approach displays a practical and rapidly implementable application of wastewater-based epidemiology to infer hospitalisation occupancy.

Performance Evaluation of Urban Water Environment Management Projects for the Protection of the Yangtze River Based on AHP-Fuzzy Comprehensive Evaluation Method

In order to promote the urban water environment management work for the protection of the Yangtze River, it is necessary to use a scientific evaluation index system to evaluate the governance effectiveness of completed management projects in pilot cities. Based on the characteristics of urban water environment management projects, this paper uses a constructed evaluation index system for the effectiveness of urban water environment management projects in the protection of the Yangtze River to evaluate the effectiveness of Phase I urban water environment management projects in Jiujiang City. The weights of each criterion layer and indicator layer were determined using the Analytic Hierarchy Process, and the fuzzy comprehensive evaluation method was used for comprehensive evaluation. The conclusions are as follows: (1) the engineering efficiency evaluation result is poor, mainly affected by the urban rain and sewage pipe network engineering criterion layer, in which the weight of the BOD5 concentration of domestic sewage in the influent of the sewage treatment plant is relatively large, and the membership degree result is poor, so attention should be paid to the BOD5 concentration of the sewage treatment plant within the scope of the project. (2) the engineering benefit evaluation result is generally good, and this evaluation result can reflect the overall benefits of the Phase I urban water environment comprehensive management project to the "plant-network-river-lake-shore" within the scope of Jiujiang City, but it is only reflected significantly by the surface water improvement contribution criterion. The reflection of social and economic aspects is not obvious, and follow-up research needs to increase the participation of residents through questionnaires or field surveys to make the results more reflective of the economic and social benefits.

Physio-chemical characterization of sewage sludge generated from sewage treatment plant at Varanasi, in relation to nutrients and heavy metals for agriculture use

Large amount of sewage sludge is generated during waste water treatment at sewage treatment plant (STP), as a result of the sedimentation and suspension of particles. The safe disposal and management of this concentrated sewage sludge posesa major challenge for town and city municipal corporations. However, this could also be used in agriculture as an input to partially replace recommended doses of fertiliser. Thus, the current study was conducted to investigate the physio-chemical and biological characteristics of sewage sludge (SS) and its potential application in agricultural fields as an organic manure. Sewage sludge samples were collected from sewage treatment plant (STP) at Bhagwanpur, Varanasi, India and sieved in 2 mm mesh before being analysed for various physical and chemical characteristics. The processed sewage sludge possessed both major [total nitrogen (1.76 %), total phosphorous (1.29%), total potassium (1.15%)] and micro nutrients (Fe, Mn, Zn and Cu) and significant amount of organic carbon (8.67 %). However, this sewage sludge was also containing considerable amount of heavy metals like Cadmium (7.3 mg kg-1), chromium (49.2 mg kg-1), nickel (total 27.43 mg kg-1), and lead (39.53 mg kg-1), which were reported to be harmful to human beings, but these were lower than threshold limit recommended by Council of the European Communities, 1988 for agricultural use. Further, Bulk density and water holding capacity was 1.18 g cm-3 and 54.5 % respectively. With respect to microfauna, fungi were found more dominating than actinomycetes and bacteria in this sewage sludge. Therefore,considering use of this sewage sludge for agriculture may decrease the use of chemical fertilisers and make it more sustainable. However, in order to increase soil health without posing an environmental risk, sewage sludge must be carefully evaluated before being applied to soil especially for heavy metals and other hazardous pollutants.

ASSESSMENT OF HEAVY METALS ACCUMULATION IN WHEAT GROWN ON SEWAGE SLUDGE-TREATED FERTILE SOIL

The application of sewage sludge to agricultural land is an increasingly popular disposal route and it can be a valuable source of nutrients for crops. Soil properties such as texture, pH value, and ion exchange capacity, strongly influence the availability of trace metals to plants. This paper aims to determine the concentrations of heavy metals (Cd, Cr, Cu, Mn, Pb, and Zn) from wheat, grown in controlled conditions, using two analytical methods as Atomic Absorption Spectrometry (AAS) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The analyzes were carried out at various stages of wheat grain growth and at different concentrations of sewage sludge/soil (0/100, 25/75, 50/50, 75/25, 100/0). The purpose of this paper is to present a method for valorizing sludge from sewage treatment plants, as well as the benefits that this method can have for the growth of cereals, while also looking at the influence and possible accumulation of heavy metals in this plant.

The Estimation of Domestic Greenhouse Gas Potential from Sewer Pipeline and the Review on Reducing Technologies

The recent accelerating global warming and its consequent disasters call for the immediate greenhouse gas (GHG) reduction. In this regard, the time has arrived to consider applying global warming potential (GWP) value of 20 years’ time-scale rather than 100 years’ one, and the importance of reducing methane emissions has rapidly increased due to its short life span. Sewer pipeline is the source of emitting methane through biological anaerobic conversion. However, it is not recognized as the official source from IPCC due to lack of data and investigation. In Korea, to our knowledge, there has been no study on GHG emissions from sewer pipeline. In the present work, at first, the amount of methane potential from domestic sewer pipeline was calculated considering various parameters. Depending on the organic concentration of sewage and its degradation rate, the potential amount ranged 3.2-13.4 m ton CO<sub>2</sub> eq./yr, when GWP100 value was considered. By using GWP20, this amount could reach up to 40.2 m ton CO<sub>2</sub> eq./yr, which exceeds the current total domestic methane emissions (27.8 m ton CO<sub>2</sub> eq./yr in 2019). The calculation results clearly tells the importance of developing technologies for reducing GHG from sewer pipeline. Later on, the former technologies were largely divided into chemical and physical methods, and reviewed by each. In addition, the limitation of current technologies were mentioned with addressing future works. In Korea, this is the first study regarding on GHG from sewer pipeline, which will be used for estimating the exact amount and establishing carbon neutrality.

Wastewater Surveillance of Pharmaceuticals and Genes: Challenges and Opportunities

Wastewater-based epidemiology (WBE) using viral nucleic acids to predict community viral outbreaks has many challenges, including interferences from the wastewater matrix. Liquid chromatography with tandem mass spectrometry (LC–MS/MS) monitoring of pharmaceutically active compounds, such as antivirals and over-the-counter drugs commonly used to relieve the symptoms of infection, could complement information provided by molecular techniques. For instance, residues of drugs associated with managing Covid-19 symptoms, including azithromycin, chloroquine, hydroxychloroquine, and lopinavir, have been detected in influent wastewater. A significant correlation can be observed between the total of Covid-19–related drugs detected and the 5-day rolling averages of reported cases. Spikes in acetaminophen concentrations can also be observed a couple of weeks before a spike in SARS-CoV-2 RNA copies in wastewater, suggesting that over-the-counter analgesic concentrations in raw sewage may be used to complement viral RNA data as an early-warning system for effective management of viral outbreaks at the community level. Sample preparation and analysis of pharmaceuticals in wastewater present unique challenges and are discussed in this article.

Investigation of airport sewage to detect importation of poliovirus, Poland, 2017 to 2020

BackgroundPolioviruses are human pathogens which may easily be imported via travellers from endemic areas and countries where oral polio vaccine (OPV) is still routinely used to polio-free countries. Risk of reintroduction strictly depends on polio immunisation coverage. Sustaining a polio-free status requires strategies that allow rapid detection and control of potential poliovirus reintroductions.AimThe aim of this study was to apply environmental surveillance at an international airport in Poland to estimate the probability of poliovirus importation via air transport.MethodsBetween 2017 and 2020, we collected 142 sewage samples at Warsaw Airport. After sewage concentration, virus was isolated in susceptible cell cultures. Poliovirus isolates were characterised by intratypic differentiation and sequencing.ResultsSeven samples were positive for polioviruses. All isolates were characterised as Sabin-like polioviruses type 3 (SL-3). No wild or vaccine-derived polioviruses were found. The number of mutations accumulated in most isolates suggested a limited circulation in humans. Only one SL-3 isolate contained seven mutations, which is compatible with more than half a year of circulation.ConclusionSince OPV was withdrawn from the immunisation schedule in Poland in 2016, detection of SL-3 in airport sewage may indicate the events of importation from a region where OPV is still in use. Our study shows that environmental surveillance, including airport sewage investigation, has the capacity to detect emerging polioviruses and monitor potential exposure to poliovirus importation. Poliovirus detection in sewage samples indicates the need for sustaining a high level of polio immunisation coverage in the population.

A Novel Hybrid Reactor of Pressure-Retarded Osmosis Coupling with Activated Sludge Process for Simultaneously Treating Concentrated Seawater Brine and Wastewater and Recovering Energy.

As an attractive way to deal with fresh water shortage, membrane-based desalination technologies are receiving increased interest. However, concentrated seawater brine, in needing further treatment, remains a main obstacle for desalination via membrane technology. Here, a hybrid technology integrating pressure-retarded osmosis with activated sludge process (PRO-MBR) was applied for simultaneously treating concentrated seawater brine and municipal wastewater. Performance of the PRO-MBR, including water flux, power density, contaminants removal, and membrane fouling was evaluated and compared at two different membrane orientations (i.e., active layer facing feed solution (AL-FS) mode and active layer facing draw solution (AL-DS) mode). During the PRO-MBR process, the municipal wastewater was completely treated regardless of the membrane orientation, which means that there was no concentrated sewage needing further treatment, owing to the biodegradation of microorganisms in the bioreactor. In the meantime, the concentrated brine of seawater desalination was diluted into the salinity level of seawater, which met the standard of seawater discharge. Owing to the high rejection of forward osmosis (FO) membrane, the removal efficiency of total organic carbon (TOC), total phosphorus (TP), ammonia nitrogen (NH4+-N), and total nitrogen (TN) was higher than 90% at both modes in the PRO-MBR. In addition, the PRO-MBR can simultaneously recover the existing osmotic energy between the municipal wastewater and the seawater brine at both modes. Compared with the AL-DS mode, the AL-FS mode took a shorter time and achieved a bigger power density to reach the same terminal point of the PRO-MBR owing to a better water flux performance. Furthermore, the membrane fouling was much more severe in the AL-DS mode. In conclusion, the current study demonstrated that the PRO-MBR at the AL-FS mode can be a promising and sustainable brine concentrate and municipal wastewater treatment technology for its simultaneous energy and water recovery.

Ecological engineering practice of cascade-pond system: Water purification and biodiversity conservation

With the aggravation of agricultural pollution and habitat degradation, ecological engineering has been applied to solve those contradictions. One of the effective strategies for agricultural pollution and biodiversity conservation in hilly areas is to build the cascade-pond system. In this project, the cascade-pond system was built as agricultural facilities for sustainable development in Lieshen village of Liangping district, China. In order to analyze the purification effect of aquaculture pollution and the characteristics of the macroinvertebrate assemblages in the cascade-pond system, aquatic macroinvertebrates and environmental variables were sampled at three times in one year. The results showed that the cascade-pond group in the middle reach had lower purification function to the aquaculture pollution from the upstream fish pond, which might be due to the low concentration of sewage from upstream. Higher concentration of nutrients, little macrophytes and plenty of fish in the fish ponds, did harmful to the macroinvertebrate assemblages. Meanwhile, the cascade-pond group in the middle reach with lower concentration of nutrients, abundant macrophytes and less fish could support higher biodiversity of macroinvertebrates. In the cascade-pond group, with the decrease of nutrients, the productivity of macroinvertebrates was limited by oligotrophic condition. In addition to water purification and biodiversity conservation, the system also could provide ecosystem services as hydrological regulation, soil and water conservation, economic production, leisure and entertainment. The study can offer practical model for sustainable development of agriculture in hilly areas and provide data support for the protection of regional biodiversity.

Prediction of household wastewater treatment systems' in situ performance based on standardized tests.

This paper presents a comparative analysis on operating conditions of onsite wastewater treatment systems. Actual EU Member States' national regulations require in situ treatment thresholds expressed in effluent concentrations. CE marking of onsite wastewater treatment system is mandatory according to standardized test (EN 12566-3 + A2) with performance declared in removal efficiency. Recent study indicates that in situ raw sewage concentrations are 1.5 times higher than those on test platforms. In this context, performance comparison between platform tests and in situ discharge threshold cannot be based on effluent concentrations but rather on removal efficiency to fulfill environmental and health requirements. This study compares: (i) results from eight standardized tests, (ii) over 300 measurements of in situ raw sewage, and (iii) several national-level thresholds focusing on carbon parameters. To meet French effluent thresholds, a minimum removal efficiency of 96% in SS and 95% in BOD5 is required. A beta law model assesses the efficiency measured during standardized testing and establishes a robustness characteristic with a probability above 80%. When a septic tank is used, its efficiency can be incorporated into the prediction. Although the new performance criteria are more stringent, some of the eight products evaluated still meet the requirements.

Study on the Effect of Membrane Active Surface Orientation in OMBR on Norfloxacin Wastewater Treatment

The forward osmosis membrane bioreactor (OMBR) is a kind of new treatment technology which applied forward osmosis technology to the membrane bioreactor. In this paper, the OMBR was adopted to tackle with the typical antibiotic wastewater.The influence of orientation was investigated. The results showed that the magnesium chloride solution with high osmotic pressure is advantageous for OMBR due to its superior membrane flux and a better producing water quality and the membrane flux decreases with a rise of the concentration of sewage and sludge. In this condition, the removal rate of COD and norfloxacin is 84.21% and 93.70%, respectively.

Cleaning of concentrated emulsion sewage of electric-weld pipe lines

Existing processes of cleaning emulsion sewage are based on either physicochemical technology with application of complex of reagents – nonorganic electrolytes and organic flocculants, resulting in obtaining highly-mineralized purified water, which cannot be used for technical water supply, or based on complicated technologies of electrocoagulation and ultrafiltration. This required elaboration of a new technology and equipment for cleaning concentrated emulsion sewage, in particular, those containing emulsol of Wedolit EP-5 grade, used for hydro-mechanical expanders of electric-weld pipe lines. The technology stipulates a successive introduction of a reagent – suspension of alumo-silicate based hard-phased sorbent and solution of flocculant of cation type Praestol-650ВС – into emulsion sewage, their mixing with emulsion water in a definite mode, sedimental differentiation of the formed phases in a precipitator-flocculator “ЭП ОФ”, gravitation concentration and dewatering of the obtained sediment at vacuumfilter. The dewatered sediment can be utilized in cement industry and metallurgy. It was shown that application of the hard-phase sorbent does not result in an increase of mineralization of purified water and enables to use it for technical purposes. The group of companies “ECO-PROJECT”, Ekaterinburg, accomplished a project for Chelyabinsk pipe-rolling plant, elaboration and manufacturing of equipment, as well as commissioning and start-up of the equipment. The elaborated technical solutions in the process of equipment running showed a high efficiency and can be used as a base for creation of facilities of any productivity for cleaning multi-type emulsion sewage at enterprises of various industries.

IMPACT OF SEWAGE ON PLANKTON PRODUCTION

Waste water particularly the sewage water is a readily available biodegradable nutrient rich resource and reuse of the effluent can enhance the water productivity through plankton production. A study was carried out to assess the abundance and fluctuations of plankton and productivity in different concentration (25%, 50%, 75% and 100%) of sewage water. Selected relevant water parameters such as temperature, pH, dissolved- oxygen (DO), alkalinity, hardness, ammonia -nitrogen (NH3 -N), phosphate- phosphorous (PO4 -P), nitrate-nitrogen (NO3 -N), biological oxygen demand (BOD), chemical oxygen demand (COD), total solid (TS) and total dissolved solid (TDS) in sewage effluent in different treatments were monitored along with certain biological parameters viz. plankton production and primary productivity. The primary productivity and plankton production were observed to be significantly higher (P<0.05) in 100% concentrated sewage water than the other treatments. Key words: Waste water, productivity, plankton

Effect of Chemical Oxygen Demand Concentration on Nutrient Removal in Simultaneous Nitrification, Denitrification and Phosphorus Removal System in High-Altitude Areas

The application of biological nitrogen and phosphorus removal processes in high-altitude areas faces severe challenges due to low temperature, low atmosphere pressure and low oxygen concentration. In this study, a simultaneous nitrification, denitrification and phosphorus removal (SNDPR) system was operated under low atmosphere pressure. The chemical oxygen demand (COD) concentrations in influent were decreased from 300 mg/L (stage I) to 200 mg/L (stage II), corresponding to the low COD concentration of sewage in high-altitude areas. The removal of COD and total phosphate was efficient at the H1 reactor (72 kPa). The removal rates of COD and total phosphate were 94.08% (stage I), 90.66% (stage II) and 98.43% (stage I), 99.34% (stage II), respectively, which were similar to L1 (100 kPa). The removal rates of total inorganic nitrogen and simulation nitrification and denitrification were from 81.21% (stage I) and 59.48% (stage I) to 72.86% (stage II) and 31.95% (stage II), respectively, which were also improved compared to L1. Cycle experiment results indicated that the activity of phosphorus accumulating organisms was enhanced, while the ammonia oxidation process was inhibited under low atmosphere pressure.

Simulation and optimisation of opened sewage concentration air cycle combined with the heat pump under actual weather conditions

Opened air cycle is a promising sewage concentration technology using heated air as the medium to absorb water from the sewage. Unlike closed cycles, the air flow is directly ejected out of the system after humidification in opened cycles. Operating conditions and the circle’s efficiency are highly affected by the weather, such as the time-varying ambient temperature and relative humidity. Since the evaporating temperature relies on the ambient temperature, to restrain its dependence, the evaporator was proposed combined with the ejected air flow in this paper. Such a design could improve the efficiency of the heat pump by increasing its evaporating temperature. Simulation of the newly proposed open sewage concentration cycle was performed to investigate its thermal process and economic efficiency under actual weather conditions. Thermodynamic models of the compressor, heat exchangers and the sewage concentration chamber were established. Climatic conditions at Xi’an, China were referenced as actual weather conditions. Optimisation of the working parameters was performed to achieve higher economic index. The results demonstrated that the average monthly power consumption of the optimized cycle was 0.3508 kWh/kg. Compared with the published data of the closed cycle, the total cost of new opened cycle was nearly one-third lower.