Wastewater Treatment Units Research Articles

Wastewater treatment effectiveness is facilitated by crucial bacterial communities in the wetland ecosystem.

Microorganisms play essential roles in nutrient removal and biogeochemical cycling during wastewater treatment. However, little is known about the main roles of key functional bacterial communities in wastewater treatment processes. We collected 18 water samples and 15 sediment samples from the six operational subsystems of the constructed wetland, among which the contact oxidation pond, enhanced hybrid biofilm reactor, and central stabilization pond are the main wastewater treatment units in the constructed wetland, and then investigated the bacterial communities using 16S rRNA gene targeting and sequencing to address this knowledge gap. The results indicated that the composition of the bacterial community is closely related to the efficiency of pollutant removal. The abundant carbon metabolism function increased the removal of nitrate‑nitrogen (NO3--N) and total nitrogen (TN) by the contact oxidation pond by 89.84 % and 38.91 %, respectively. The overlap of ecological niches and the presence of pathogenic bacteria substantially affect effluent wastewater treatment. Second, NO3--N (p < 0.001) was the most important factor driving the bacterial community composition in water and sediments. Furthermore, the positive structure was prevalent in the cooccurrence network of water samples (87.24 %) and sediments (76.53 %) of the wetland, and this positive structure with keystone species was critical for the adaptation of the bacterial community to environmental filtration. In summary, this study reveals the distribution patterns of bacterial communities in different wastewater treatment processes and their driving factors and provides new perspectives on the link between the bacterial community composition and wastewater treatment.

Suitability of urban river water for irrigation: the case of the Houet river in Burkina Faso

This study focused on the suitability of using an urban river for the irrigation of vegetable crops. The relevant urban river is Houet river located in the city of Bobo-Dioulasso (Burkina Faso) receives wastewater released by a wastewater treatment and purification unit (WWTP). To do this, a diagnosis of the functioning of WWTP and an assessment of the quality of the effluents released in the river were indeed carried out. The WWTP treats wastewater from industries, households and the percolating water from the treatment of the city's sewage sludge. Water released by the WWTP has a poor physico-chemical quality and high microbiological pollution. The urban river water suitability for irrigation was carried out by taking 8 water samples from the river sections at upstream and downstream parts of the WWTP junction. The physico-chemical (pH, EC, STD, Ca2+ , Mg2+ , K+ , Na+ , Cl-, HCO3- , PO43- , NO2- , NO3- , NH4+ ), microbiological (total coliform, fecal coliform, Escherichia coli and fecal Streptococci), trace metallic elements (Ni, Cr, Zn, Cu, Al, Fe and Mn) and indices such as sodium adsorption rate (SAR), percentage of soluble sodium (%Na), permeability index (PI), magnesium adsorption ratio (RAM) and Kelly ratio (RK) were analyzed and the results compared with WHO, FAO and USSL guidelines for irrigation water. The results show that the physico-chemical parameters are in line with the WHO and FAO standards for irrigation. However, the river water is reported to have medium salinity with a slight to moderate degree of restriction for EC and STD. The concentrations of ammonium (NH4+), manganese (Mn) and nickel (Ni) in the river’s water have values above standard reference for irrigation water. This suggests (i) overuse of nitrogenous fertilizers, (ii) industrial and anthropogenic discharges directly into the river, (iii) and an incomplete treatment process of water released by the WWTP. The presence of Total Coliforms, Fecal Coliforms, Escherichia coli and Fecal Streptococci at levels of around 104 to 109 CFU/100ml, above the FAO standard (2000 CFU/100ml), indicate that the river water is probably contaminated by viruses, parasites and other pathogenic bacteria of fecal origin. Houet river water is in excellent range for irrigation according to Wilcox diagram and in the C2 S1 range of medium to good quality according to the Riverside diagram. The SAR, %Na, PI, RAM and RK indices showed that the infiltration problem issue of the river water on irrigated soils is low before its junction with the WWTP and moderate after its junction. Overall, this river water is suitable for irrigation, but the presence of bacteria, ammonium and trace metallic elements require for the regional water and agricultural authorities to (i) pay particular attention to human activities in the vicinity of the river, (ii) improve the efficiency of the wastewater treatment process at the WWTP and (iii) more strictly control fertilizers’ uses by market gardeners. This will make it possible to preserve the quality of the river’ water for the irrigation of 175 hectares of market gardens products (lettuce, parsley, pepper, mint…) using a commercial urban outland to feed an urban population estimated of one million people.

Design of Influent Distribution System in Domestic Wastewater Treatment Units

The efficient treatment of domestic wastewater is associated with good operational practices in wastewater treatment plants (WWTP) and the proper design of each treatment unit, which ensures the correct hydraulic performance of each WWTP. For this reason, the objective of this article was to study the design of the multiple influent distribution systems of a high-rate primary sedimentary, a UASB (Upflow Anaerobic Sludge Blanket) reactor, and an up-flow anaerobic filter (FAFA) in the WWTPs of the municipalities of San Carlos and San Roque, and in the township of Santiago, respectively, located in Antioquia-Colombia. For this purpose, the methodology proposed by Hudson in 1981 was used to evaluate the performance of the current design and, subsequently, a pre-dimensioning was carried out to distribute the flow uniformly, to have velocities within the ranges recommended by the literature, and to obtain the total head loss generated by the distribution manifold in each treatment unit evaluated. It was found that the existing design is not efficient and that the new pre-dimensioning ensures homogeneous flow distribution and provides velocities that contribute positively to the treatment process. The study concludes that the smaller the number of orifices and the larger the pipe diameter, the more uniform the flow distribution, and that the total head loss depends on both the velocity head and the head loss coefficient. The diameter of the orifice was the predominant parameter to control the inlet velocity of the treatment units.

Optimization model for cost estimation of decentralized wastewater treatment units

In this study, an optimization model, which is a combination of Genetic algorithm (GA) and geographical information system (GIS) was used to find minimum construction, operation, and flow reuse cost ( Fmin) . This Fmin model will be used for the estimation of the constructional and operational costs of decentralized wastewater treatment units [DTUs] and can be used for the estimation of reusing treated municipal wastewater flow for irrigation purposes in Sulaimani city, Iraq as well. In the optimization processes, an objective function technique was used based on data from 31 small-sized DTU and the costs of reusing their effluents in 827 deferent sizes green areas [GRs] across the city. A transportation matrix model of size [31x827] was built to find the Fmin for conveying the required flow from the DTUs to the GRs destinations. Also, optimum required pipe lengths and routes for the treated flow conveying were found using GIS Network Analysis – Origin-Destination (OD) Matrix Tools. The results showed that the proposed model could successfully obtain an optimal solution. The algorithm is flexible enough to consider a variety of scenarios and compare the best options.

A Novel 4-Set Venn Diagram Model Based on High-Resolution Mass Spectrometry To Monitor Wastewater Treatment.

A 4-set Venn diagram model oriented to high-resolution mass spectrometry (HRMS) data was developed to decipher the fate of dissolved organic matters (DOM) in three-stage continuous wastewater treatment processes. In total, 24 typical wastewater treatment modes conceptualized into a combination of three stages were generalized so that this model can be applied to all common types of actual wastewater treatment processes. As a result, eight kinds of native DOM and seven kinds of wastewater-produced (WW-produced) DOM separately represented by each proper subset of the 4-set Venn diagram could be identified so as to offer a molecular profile of DOM transformation. The 15 proper subsets of the 4-set Venn diagram could then explain how different wastewater treatment units work. Transformation rates of each DOM molecular formula can be estimated as a semiquantitative result. We further discussed the relationship between the transformation rates and proper subsets. As a proof of concept, the 4-set Venn diagram model was successfully applied in a complicated full-scale mature leachate treatment process with nine treatment units. This model can help to overcome the challenging task of data mining when applying HRMS and reduce the workload of data screening in the subsequent structural annotation.

Dynamic modeling of recirculating aquaculture systems: Effect of management strategies and water quality parameters on fish performance

Growing concerns regarding the sustainability of the aquaculture industry has led to the development of recirculating aquaculture systems (RAS) where the addition of wastewater treatment units is accompanied by a reduction in water consumption and waste release. In this study, a mechanistic dynamic model of RAS is presented and validated using experimental data available in the literature. Fish health is crucial to the profitability of an aquaculture facility. Therefore, fish growth and mortality relations are considered to predict fish well-being under different environmental conditions and management strategies. Insights gained from this model can lead to better decisions in the operation of RAS and thus improve fish welfare.

Explainable multisensor fusion-based automatic reconciliation and imputation of faulty and missing data in membrane bioreactor plants for fouling alleviation and energy saving

A membrane bioreactor (MBR) is a crucial wastewater treatment unit that requires continuous and precise monitoring to ensure stable operation and avoid energy loss. Sensor malfunction in MBR plants leads to missing and faulty measurements that negatively affect the control of membrane fouling and energy consumption. This study proposes an intelligent monitoring system to alleviate membrane fouling by the autonomous handling of sensor malfunctions in MBR plants using explainable AI (XAI) and a new multisensor fusion-based automated data reconciliation and imputation (MSF-ARI) approach. Missing and faulty data cases were used to validate the MSF-ARI approach in imputing the consecutive and point-to-point missing values and the detection, diagnosis, and reconciliation of the faulty data. Then, XAI analysis and an integrated biological-physical MBR model were utilized to evaluate the effect of MSF-ARI on membrane fouling and energy consumption. The results showed that the proposed MSF-ARI presents a superior missing data imputation performance (MAE = 0.31 mg/L) and a high reconciliation of the faulty measurements (MAE = 1.96 mg/L) along with a high detection rate (DRSPE = 100 %) and well-diagnosed fault groups. Applying MSF-ARI, the early membrane fouling was avoided by preventing the increased accumulation of the stable sludge cake, leading to a prolonged MBR operation by 10 days with an energy saving of 37.44 %. Therefore, managing faulty and missing data by MSF-ARI could contribute to the mitigation of membrane fouling and achieve a sustainable balance between operational time and energy consumption.

Comprehensive Evaluation of Odor-Causing VOCs from the Painting Process of the Automobile Manufacturing Industry and Its Sustainable Management

Automotive manufacturing is one of the potential sources of air pollution particularly involving volatile organic compounds (VOCs). This study intensively evaluated VOC emissions and their dispersion from the industry. The measured VOCs were speciated for further evaluation of their odor threats according to the characteristics of each compound. Mathematical emission and air dispersion models were applied to assist in elaborating the source–receptor relationship allowing the determining of existing business-as-usual conditions with proposed mitigation measures to manage the pollution of the factory studied in this paper. Seven VOC species potentially caused odor problems to the surrounding community, including 1-butanol, ethyl benzene, toluene, m,p xylene, o xylene, methyl ethyl ketone, and methyl isobutyl ketone. The results from the AERMOD dispersion model revealed that the smell from these chemicals could reach up to about 800 m from the source. Analysis of mitigation measures indicated that two interesting scenarios should be considered according to their effectiveness. The concentrations of VOCs can decrease by up to 4.7, 14.0 and 24.9% from increasing the physical stack height by +1, +3 and +5 m from its existing height, respectively. Modification of the aeration tank of the wastewater treatment unit to a closed system also helped to reduce about 27.8% of emissions resulting in about a 27.6% decreased ambient air concentration. This study provided useful information on the characteristics of VOCs emitted by the automobile manufacturing industry. It also demonstrated the relevant procedures and highlights the necessity to comprehensively analyze the source–receptor relationship to evaluate the most appropriate measures in managing industrial air pollution.

Design, development and performance evaluation of skid-mounted pilot wastewater treatment and resource recovery unit for mechanical scavenging vehicle

The current work is an effort towards developing a sustainable solution towards the obnoxious practice of manual scavenging of the drainage pipelines and clogged pits in the developing countries. Here, a skid-mounted system has been developed and tested that works both as wastewater treatment and recovery unit and also for recovery of valuable nutrients that further has economic value. The initial bench scale work was carried out in two different approaches: the first targeting to a sequential process of separating the N, P in the form of struvite as a nutrient rich bio-cake followed by treatment & recovery of the supernatant liquid through AOP. The second approach intended to initially reduce the solid content of the effluent through coagulation followed by separating the nutrient laden liquid and treatment by AOPs to degrade the organic. Under the optimized condition of pH 9.5, Mg:P:NH4 at 1.1:1:1 and 20 min, maximum recovery of the nutrient was achieved. The results obtained from ozone based AOP was improved by combining a venturi-based cavitation device under optimized geometric and operating condition. Both the nutrient rich bio-cake obtained from degraded sludge in a rotating hydrodynamic cavitator as well the nutrient rich water was used as the fertilizer for studying the plant growth rate and compared with commercial fertilizer. The techno-economic study indicates that $ 0.22/m3 as operational cost for treatment and recycling of sewage wastewater using the developed skid mounted device reveals techno-economic viability and self-sustainability of the process.

Comammox Nitrospira Bacteria Are Dominant Ammonia Oxidizers in Mainstream Nitrification Bioreactors Emended with Sponge Carriers.

Complete ammonia oxidation (i.e., comammox) is a newly discovered microbial process performed by a subset of the Nitrospira genus, and this unique microbial process has been ubiquitously detected in various wastewater treatment units. However, the operational conditions favoring comammox prevalence remain unclear. In this study, the dominance of comammox Nitrospira in four sponge biofilm reactors fed with low-strength ammonium (NH4+ = 23 ± 3 mg N/L) wastewater was proved by coupling 16S rRNA gene amplicon sequencing, quantitative polymerase chain reaction (qPCR), and metagenomic sequencing. The results showed that comammox Nitrospira dominated in the nitrifying guild over canonical ammonia-oxidizing bacteria (AOB) constantly, despite the significant variation in the residual ammonium concentration (0.01-15 mg N/L) under different sets of operating conditions. This result indicates that sponge biofilms greatly favor retaining comammox Nitrospira in wastewater treatment and highlights an essential role of biomass retention in the comammox prevalence. Moreover, analyses of the assembled metagenomic sequences revealed that the retrieved amoA gene sequences affiliated with comammox Nitrospira (53.9-66.0% read counts of total amoA gene reads) were always higher than those (28.4-43.4%) related to β-proteobacterial AOB taxa. The comammox Nitrospira bacteria detected in the present biofilm systems were close to clade A Candidatus Nitrospira nitrosa.

Integration of wastewater treatment units and optimization of waste residue pyrolysis conditions in the brominated phenol flame retardant industry

Among the bromine flame retardants, tetrabromobisphenol A (TBBPA) is a highly effective flame retardant that can be used as both reactive and additive. However, the synthesis reaction of TBBPA has a low conversion rate and many brominated phenolic organics. Therefore, there is an urgent need to remove brominated organic pollutants produced in the process of producing flame retardants to reduce the harm to the environment and human beings and to reduce production costs. In this study, an efficient process was developed to treat the wastewater and waste residue generated in TBBPA production process, realizing its harmless and resource utilization. In the resource utilization system, through the ingenious design of solution mixing, precipitation separation, three-effect evaporation and concentration, valuable substances were extracted to realize the recovery and reuse of wastewater. In the harmless utilization process of hazardous waste residue, through high-temperature pyrolysis at 500 °C for 2 h after optimization with hypoxia-hyperoxia atmosphere modulation, it can avoid the production of dioxins and carbon black, effectively remove the organic impurities, realize the harmlessness and obtain high-quality sodium sulfate. This paper aims to propose a simple, efficient and feasible utilization system, including the three major technological processes of TBBPA production, integrated wastewater treatment and optimized the harmless treatment of waste residue to obtain sodium sulfate, so as to realize TBBPA green production. Compared with the traditional TBBPA synthesis system, wastewater and waste residue treatment processes, the TBBPA quality is increased by 2 % and the economic cost is reduced by 10 %, which is of great significance to the development of the industry.

Flocculating microscale zero-valent iron (mZVI) improves its hydrodynamic properties for wastewater treatment

Microscale zero-valent iron (mZVI) powder is dense due to the presence of metallic iron (Fe(0)). Herein, we show that the dense mZVI has several hydrodynamic problems in wastewater treatment unit operations (WTUO), and an mZVI modification method using inorganic floc is proposed and studied to solve the problems. Specifically, mZVI particles are flocculated using Fe(OH)2 or Al(OH)3 floc, forming a mZVI-floc combination ((mZVI)a(floc)b) in which mZVI is embedded in the floc. The (mZVI)a(floc)b is then characterized at hydrodynamic conditions simulating those of large-scale WTUO (e.g., mechanical mixing and gravitational settling). The study demonstrates that 1) the combination is better in mixedness during the mixing, in settleability during the settling and in fluidity in the concentrated form; 2) the mZVI remains embedded in or attached to the floc during the mixing. The study also provides physical and rheological data about the (mZVI)a(floc)b, such as size, bulk density and apparent viscosity. The improvement in hydrodynamic properties is attributed to the low particle density after the flocculation, which is less than one tenth to that of the bare mZVI. Comparative experiments show no reactivity inhibition of the floc on the embedded mZVI. The recommended floc/mZVI molar ratio for practical use is ≥0.5:1, with the influent pH adjusted to ∼6.2 (for Al(OH)3) or ∼8.9 (for Fe(OH)2); it is also suggested that these operating parameters can be determined on a case-by-case basis via bench- and/or pilot-scale experiments studying the treatment efficiencies and evaluating the overall treatment cost. The flocculation method makes mZVI more adaptable to the large-scale wastewater treatment applications (e.g., the treatment plant retrofitting). The work is also the 1st report about mZVI hydrodynamics for wastewater treatment and provides study methodology for this topic.

Distributed wastewater treatment offers an environmentally preferable alternative to conventional septic systems in Central Florida.

Wastewater management is a critical issue globally. In Florida, the importance of this issue is heightened by the proximity to sensitive ecosystems. Distributed wastewater treatment units (DWTU) are a recent, state-approved alternative to septic system conversions to centralized sewer infrastructure. In this study, the performance of a DWTU was tested at a new residence in Lake Hamilton, FL. A monitoring well was installed downgradient of the DWTU absorption field to establish baseline groundwater conditions prior to occupation of the residence. The residence was occupied, after which groundwater, DWTU influent, and effluent samples were collected. Many effluent parameters significantly decreased compared to influent, including ammonia (NH3; 97%), total Kjeldahl nitrogen (TKN; 95%), total nitrogen (TN; 88%), the TN:TP ratio (84%), fecal coliforms (92%), carbonaceous biochemical oxygen demand (CBOD; 96%), and total suspended solids (TSS; 96%). In the groundwater, nutrient concentrations initially increased compared to the baseline data, but eventually decreased, demonstrating that the DWTU was effective at improving quality of wastewater effluent. These systems could be especially effective in sensitive areas where advanced wastewater treatment has been mandated or is needed.

Concentration and reduction efficiency of vancomycin-resistant heterotrophic bacteria and vanA and vanB genes in wastewater treatment unit processes

ObjectivesThis study elucidated the distribution and fate of vancomycin (VCM)-resistant heterotrophic bacteria (HTB) and resistance genes, vanA and vanB, during each treatment unit process of a wastewater treatment plant (WWTP). MethodsSeveral bacterial counts as well as copy numbers of vanA and vanB genes were determined in each wastewater and sludge sample. In addition, HTB strains isolated from wastewater and sludge were analyzed for VCM susceptibility. Then, the fate and reduction ratios of each bacterial count, copy number of vanA and vanB genes, and the existence ratio of VCM-resistant HTB strains in the wastewater treatment unit process were evaluated. ResultsVCM-resistant HTB were detected in all wastewater and sludge samples, and their existence ratio decreased along the treatment process (92.9% in influent wastewater to 39.4% in chlorinated water). Notably, most of the HTB isolated from the influent wastewater were resistant to 8.0 µg/mL of VCM, strongly suggesting that a significant number of antibiotic-resistant bacteria are flowing into the WWTP from urban areas through the sewage system. The vanA and vanB genes were also detected in all wastewater and sludge, with high copy numbers (102-104 copies/mL) even in chlorinated water samples. ConclusionsResults revealed that residual VCM-resistant HTB, and resistance genes, which could not be completely removed, were ubiquitously released into the aquatic environment. Furthermore, a high existence ratio of VCM-resistant HTB and high copy numbers of resistance genes were also detected in the sludge, indicating that they are constantly circulating in the WWTP via the returned sludge.

Enhanced hydrolytic removal of tylosin in wastewater using polymer-based solid acid catalysts converted from polystyrene

Antibiotic production wastewater usually contains high concentrations of antibiotic residues, which can cause instability and deterioration of biological wastewater treatment units and also domestication and proliferation of antibiotic-resistance bacteria. An effective pretreatment on antibiotics production wastewater is expected to selectively reduce the concentration of antibiotics and decrease the toxicity, rather than mitigate organic and other contaminants before further treatments. In this work, two polymer-based solid acids, PS-S and CPS-S bearing high concentrations of -SOH3 groups (up to 4.57 mmol/g), were prepared and successfully used for hydrolytic mitigation of 100 mg/L tylosin within 20 min. The co-existence of high concentrations of COD and humic substances did not affect the mitigation of tylosin obviously, while more than 500 mg/L of nitrogenous compounds suppressed the hydrolytic efficiency. Recycle and reuse experiments showed that the solid acids performed well in five cycles after regeneration. Three transformation products (P1, P2 and P3) were identified using UPLC-QTOF-MS/MS. Sugar moieties including mycarse, mycaminose, and mycinose detached and released simultaneously or in order from the 16-member lactone ring through desugarization, which led to a dramatic decrease in antibacterial activity as revealed by cytotoxicity evaluations using S. aureus. Ecotoxicity estimation indicated the acute toxicities of the hydrolyzed products to model species (e.g., fish, daphnid and green algae) were classified as “not harmful”. This work suggested an effective and selective method to pretreat tylosin-contained production wastewater by using polymer-based solid acids. These results will shed light on effective elimination of antibiotics pollution from pharmaceutical industries through strengthening the pretreatments.

Occurrence and migration of microplastics and plasticizers in different wastewater and sludge treatment units in municipal wastewater treatment plant

Occurrence and migration of microplastics and plasticizers in different wastewater and sludge treatment units in municipal wastewater treatment plant

Treating High COD Dyeing Wastewater via a Regenerative Sorption-Oxidation Process Using a Nano-Pored Activated Carbon.

Nowadays, the structural complexity of dyes used in the textile industry and the widely adopted water-saving strategy in the dyeing processes often fail plants’ biological wastewater treatment units due to chemical oxygen demand (COD) overload. To alleviate this problems, this study investigated a regenerable adsorption–oxidation process to treat dyeing wastewater with COD around 10,000 mg/dm3 using a highly nano-pored activated carbon (AC) as a COD adsorbent, followed by its regeneration using hydrogen peroxide as an oxidizing reagent. In addition to studying AC’s COD adsorption and oxidation performance, its operational treatment conditions in terms of temperature and pH were assessed. The results firstly demonstrated that about 50–60% of the COD was consistently adsorbed during the repeated adsorption operation before reaching AC’s maximum adsorption capacity (qmax) of 0.165 g-COD/g-AC. The optimal pH and temperature during adsorption were 4.7 and 25 °C, respectively. Secondly, AC regeneration was accomplished by using an initial peroxide concentration of 2.5% (by wt %) and EDTA-Fe of 2.12 mmole/dm3. The reuse of the regenerated ACs was doable. Surprisingly, after the first AC regeneration, the COD adsorption capacity of the regenerated AC even increased by ~7% with respect to the virgin AC. Thirdly, the results of a five-consecutive adsorption–regeneration operation showed that a total of 0.3625 g COD was removed by the 5 g AC used, which was equivalent to an adsorption capacity (q) of 0.0725 (= 0.3625/5) g-COD/g-AC during each adsorption stage. Based on the obtained results, a regenerable COD adsorption–oxidation process using a nano-pored AC to treat the high-textile-COD wastewater looks promising. Thus, a conceptual treatment unit was proposed, and its potential benefits and limitations were addressed.

Cleaner production and carbon reduction target: Analysis of sewage treatment plants in Nort-Central China

ABSTRACT In order to realize cleaner production of Sewage Treatment Plants and reduce the emission of carbon, the current situation of various sewage treatment plants of varying scales in Nort-Central China from 2019 to 2020 was investigated. For contrast, the energy consumption and material consumption of each sewage treatment plant and their cleaner production potential were analyzed. The results revealed that the implementation of a cleaner production scheme in the 14 investigated sewage treatment plants resulted in a cost reduction of 2.13 million annually. Further, the energy-saving effects of the cleaner production schemes of the sewage treatment plants were compared, and the results revealed that the use of a magnetic levitation fan reduced the power consumption of the wastewater treatment unit and carbon emission by 13.16–17.87 and 4.58–7.69%, respectively. In addition, the utilization of a modified precise aeration system reduced the wastewater power consumption and carbon emission by 2.8–6.33 and 10.37–17.24%, respectively. This study demonstrates that the Sewage Treatment Plants can become cleaner by using magnetic levitation fan and precise aeration system. The paper highlights the value of increased energy efficiency and reduction of greenhouse gas emissions.

Environmental Aspects of the Combined Cooling, Heating, and Power (CCHP) Systems: A Review

Expanding cities means increasing the need for energy in the residential sector. The supply of this energy must be in environmentally friendly ways; one method of meeting demand in the residential sector is the use of combined cooling, heating, and power (CCHP) systems. The current review paper shows that due to the high cost of gas and electricity, CCHP can be used in various sectors, such as hospitals and airports, to reduce energy consumption with lower environmental impacts by using renewable energy systems as the main driver. While CCHP systems are not feasible in tropical regions with high cooling demand, a solar hybrid system is a superior candidate for regions with sufficient radiation. CCHP can also be used in sectors such as wastewater treatment units, desalination systems, and hydrogen production units to improve performance and increase productivity. The carbon and water footprints of CCHP systems are discussed in detail. The main drivers for reducing carbon and water footprints are improving system components such as the combustion engine and increasing productivity by expanding the system to multi-generation systems. Finally, the carbon tax index can help reduce carbon emissions if properly used in the right context. Based on our best knowledge, there is no extensive review of the environmental aspects of CCHP systems in the literature.

Evaluation of operational parameters for the removal of turbidity and total coliform from wastewater using fabricated electrocoagulation treatment unit

The purpose of this study was to design and fabricate a prototype electrocoagulation wastewater treatment unit. The treatment system consist of wastewater storage tank, reactor tank with electrodes, treated water collection tank, filtration unit, filtered water storage tank, DC power supply. The study focuses on the effect of electrocoagulation treatment unit on treatment of wastewater containing physical and biological impurities using aluminium and iron electrodes. The aluminium electrodes used as anode and iron electrodes used as cathode. This study was based on treatment of synthetic wastewater containing turbidity and total coliform colonies. The unit was optimized at various operating conditions including pH, current density, and contact time. Impurities removal efficiency of designed Electrocoagulation (EC) unit was investigated at various conditions. Batch flow system was used for operation of reactor. From the experiments, the best turbidity removal efficiency was 94% at 6.5 pH, 18 mins and 3 A and for total coliform the removal efficiency was 98.95 % at 6.5 pH, 18mins and 3A. Results showed that aluminium and iron electrode are very effective electrode material for removal of physical and biological impurities cost effectively.