Average Effluent Concentrations Research Articles

Pilot scale microbial fuel cells using air cathodes for producing electricity while treating wastewater

Microbial fuel cells (MFCs) can generate electrical energy from the oxidation of the organic matter, but they must be demonstrated at large scales, treat real wastewaters, and show the required performance needed at a site to provide a path forward for this technology. Previous pilot-scale studies of MFC technology have relied on systems with aerated catholytes, which limited energy recovery due to the energy consumed by pumping air into the catholyte. In the present study, we developed, deployed, and tested an 850 L (1400 L total liquid volume) air-cathode MFC treating domestic-type wastewater at a centralized wastewater treatment facility. The wastewater was processed over a hydraulic retention time (HRT) of 12 h through a sequence of 17 brush anode modules (11 m2 total projected anode area) and 16 cathode modules, each constructed using two air-cathodes (0.6 m2 each, total cathode area of 20 m2) with the air side facing each other to allow passive air flow. The MFC effluent was further treated in a biofilter (BF) to decrease the organic matter content. The field test was conducted for over six months to fully characterize the electrochemical and wastewater treatment performance. Wastewater quality as well as electrical energy production were routinely monitored. The power produced over six months by the MFC averaged 0.46 ± 0.35 W (0.043 W m–2 normalized to the cross-sectional area of an anode) at a current of 1.54 ± 0.90 A with a coulombic efficiency of 9%. Approximately 49 ± 15 % of the chemical oxygen demand (COD) was removed in the MFC alone as well as a large amount of the biochemical oxygen demand (BOD5) (70%) and total suspended solid (TSS) (48%). In the combined MFC/BF process, up to 91 ± 6 % of the COD and 91 % of the BOD5 were removed as well as certain bacteria (E. coli, 98.9%; fecal coliforms, 99.1%). The average effluent concentration of nitrate was 1.6 ± 2.4 mg L–1, nitrite was 0.17 ± 0.24 mg L–1 and ammonia was 0.4 ± 1.0 mg L–1. The pilot scale reactor presented here is the largest air-cathode MFC ever tested, generating electrical power while treating wastewater.

The nitrogen removal performance and mechanisms for urea wastewater by simultaneous urea hydrolysis, partial nitritation and anammox in one reactor

The efficient and economical disposal of urea wastewater for promoting wastewater reuse, are still tough obstacles for the sustainable development of urea industry. In order to explore newly efficient and economical alternative for urea wastewater treatment, a novel one-stage autotrophic nitrogen removal reactor (submerged aerated biological filter, SABF) simultaneously combining with urea hydrolysis, partial nitritation (PN) and anammox was carried out and stably operated for 126 days. The SABF reactor not only presented excellent urea removal efficiency (˃ 99.5%) with average effluent urea concentration of 0.83 mg/L to meet reuse standard, but also achieved high nitrogen removal loading, ammonium removal efficiency and total nitrogen removal efficiency as 1.5 kg N/(m3·d), 89.46% and 77.09%, respectively. The urea removal mechanism was proven as the intracellular urea hydrolysis, which was conducive to accomplish the persistent free ammonia (FA) inhibition on nitrite-oxidizing bacteria for stable PN and guaranteed total nitrogen removal by anammox. High-throughput sequencing analysis results revealed that Nitrosomonas accounting for 15.92% should be responsible for excellent urea hydrolysis and PN performance and Candidatus_Brocadia with relative abundance of 1.63% was the main anammox bacteria for further nitrogen removal in the SABF reactor. The proposed process showed significant advantages of extremely low operational cost and high removal efficiency with recyclable effluent for urea wastewater treatment. This study provided a novel and superior alternative for the cleaner production of urea manufacturing enterprises, which can well alleviate the stress of urea wastewater treatment and further benefit the sustainable development of urea industry in the future.

Design and performance analysis of a renewable pumping system for treated wastewater to reuse in the Moroccan desert

Abstract Treated wastewaters are an important alternative water supply for communities in dry climates all over the world. This study investigates using waste stabilization ponds (WSPs) to treat wastewater and the design of a solar photovoltaic pumping system to transfer the water to an Oasis in the Moroccan desert. The Oasis is currently about 5 ha in size and is irrigated with 24 m3/day of underground water. The wastewater is subjected to physicochemical and bacteriological analyses, also monitoring of operation, maintenance and loading rates of the WSPs for 12 months. To build a solar water pumping system, data on the system's components as well as local climatic data are obtained. The design optimization is done by simulation software PVsyst. WSPs provide reduced rates of BOD and fecal coliforms of 95 and 99%, respectively, with an average effluent concentration of 20 mg/l and 195 CFU. The exploitation of solar energy for pumping 24 m3/day requires five panels with a unit nominal power of 440 W for each panel and 2200 W for the entire system. This allows us to save about 1,500 kg of CO2 emissions per year, protect the region's fragile water resources and ensure the sustainability of the Oasis.

Removal of cyanide from alumina smelter wastewater using precipitation and filtration technique

Aluminum is a metal that is used in many products because of its good conducting properties. However, in the production process, aluminum is not obtained easily but through a long process. In aluminum smelting process, wastewater that is produced indicates the existence of pollutants as determined by several indicators of water pollution, one of which is cyanide that will threaten human and environmental health if not treated properly. This study was conducted to determine the optimal dose of ferrous sulfate to remove cyanide, the precipitation and filtration process efficiency in reducing cyanide, and its effect on pH of wastewater. Data were collected from an aluminum smelting company, and experiments were conducted in the laboratory. Based on results, ferrous sulfate dose of 93 mg/l is the most optimal dose in removing cyanide with an efficiency of 58.74±0.51%, while filtration process provides an efficiency of 81.65±0.42%. Precipitation with ferrous sulfate makes pH value of wastewater decrease, but filtration process increases the value again. Throughout the whole process, cyanide can be reduced by a combination of precipitation and filtration process with the efficiency of 92.43±0.26% and an average final effluent concentration of 0.78 mg/L from an initial concentration of 10.3 mg/L.

Decentralized domestic wastewater management as unconventional water resource for agricultural purposes

AbstractThis research addresses biological compact unit(BCU)used for onsite wastewater treatment for application and replication in small communities as a non- conventional water resource for agricultural purposes. A (BCU) was fabricated and installed in the in-house experimental zone where the domestic sewage was delivered to the BCU continuously .Operation of the BCU was continuous, hence at different organic loading rates (OLR) and different temperatures .The treated sewage was fed from the BCU to a sand filter upper side. The treated wastewater quality produced from the BCU in terms of physico-chemical and biological characteristics at HRT 12h agree with the Egyptian permissible limits for restricted irrigation. This is because of the substantial reduction of total COD resulting in an average effluent concentration of 67 mg/l and FC of 560/100 ml. The characteristics of sand filter effluent, treating BCU effluent operated at 12h HRT in terms of COD, BOD,TSS and fecal coliform were 35 ,17 ,5 mg/l and 95/100ml. These values are compatible with national legislation for wastewater reuse in un-restricted crops irrigation. The total cost of BCU construction, operation and maintenance will be US$0.34/m3 for restricted crops irrigation. When adding a sand filter, the cost will be US$0.46 /m3 for un-restricted crops irrigation.

Improving the performance of waste stabilization ponds in an arid climate

Abstract In many parts of the world, waste stabilization ponds (WSPs) are currently the preferred wastewater treatment method for municipal wastewater. The objective of this research is to examine the performance of a WSP in an arid climate region and to identify ways to improve its purification efficiency so that it can meet the criteria for reuse. The results attributed the poor performance to both improper process and physical design after 12 months of physicochemical and bacteriological analyses, as well as monitoring of operation, maintenance and loading rates. In tertiary treatment, maturation ponds are added, an increase in the capacity of the station, and management of the flow rate and retention time for each pond. By simulating the new WSP with GPS-X, the best pond area ratio obtained is 2.5 m2/capita, with a retention time of 4 days for anaerobic ponds, 20 days for facultative ponds and 3 days for two maturation ponds in series, which is suitable and provides reduction rates of BOD and fecal coliforms of 95 and 99%, respectively, with an average effluent concentration of 20 mg/L and 195 CFU. According to the results, well-maintained WSPs provide a viable, self-sufficient and environmentally friendly wastewater treatment solution for irrigation water supply in dry areas.

Assessment of a wide array of organic micropollutants of emerging concern in wastewater treatment plants in Greece: Occurrence, removals, mass loading and potential risks

Exploring the contamination profile of multi-class emerging contaminants (ECs) in wastewater is highly desirable. To this end, the occurrence, removal, mass loading and risks associated with a large panel of pharmaceuticals and personal care products, illicit drugs, perfluorinated compounds and organophosphate flame retardants in two wastewater treatment plants (WWTPs) in the region of Thessaloniki (Greece) after a survey is illustrated. Influent and effluent wastewaters were submitted to solid phase extraction on Oasis HLB cartridges, followed by ultra-high-performance liquid chromatography Orbitrap high-resolution mass spectrometry (UHPLC–Orbitrap MS). Influent concentrations in both WWTPs were notably higher than effluent, with caffeine, acetaminophen, irbesartan and valsartan being the most ubiquitous compounds, exhibiting elevated concentrations. Average effluent concentrations ranged from below the method quantification limits (<MQL) to remarkably high values (μg L−1 scale), such as for caffeine, acetaminophen, diclofenac, irbesartan and valsartan, among others. Removal efficiencies ranged between −273% for lamotrigine and 100%, i.e., for the UV filter BP1. Notably, the polar compounds such as cytarabine, methotrexate and capecitabine were removed at a rate >80% in both WWTPs, allowing the correlation between logKow and removals. Interesting trends for the illicit drugs were revealed by means of mass loading estimation, as in the case of benzoylecgonine (71.6 mg/day/1000 inhabitants). Ecotoxicological risk assessment was evaluated for both single components and mixture, using three approaches: risk quotient (RQ), risk quotient considering frequency (RQf) and toxic units (TU). Irbesartan and telmisartan posed a high risk in all trophic levels, while fish was the most sensitive taxa for diclofenac. This work aspires to intensify the surveillance programs for the receiving water bodies, as well as to motivate the investigation of toxicity to non-target organisms.

A new Fe-C porous filter material from dredged sediment: preparation, characterization, and its application.

A new Fe-C porous filter material was prepared with dredged sediment of river as raw material. The orthogonal test L9(34) and component ratio experiment of raw material were conducted to investigate the optimum technological condition. Further, the filter obtained was characterized by Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), energy dispersive X-ray spectroscope (EDS), and X-ray diffraction (XRD). Results showed that the optimal technological condition was sludge: straw: starch: iron powder: foam: iron powder 74.5: 10: 7.5: 3: 5, preheating temperature 280 °C, preheating 15 min, sintering temperature 1080 °C, and sintering 11 min. The BET surface area of the filter was 3.32 m2 g-1, and average pore size was 10.05 nm. Phase composition mainly included SiO2, Fe3O4, Fe2O3, and muscovite (KAl2(Si3Al)O10(OH)2). Average effluent concentrations of total phosphorus (TP), total organic carbon (TOC), and total nitrogen (TN) of the biofilter system filled with the filter obtained were decreased to 0.08, 3.43, and 3.76 mg L-1, separately, at hydraulic retention time 4 h. Thus, the filter prepared with dredged sediment of rive as raw material is an alternative material for polluted river water purification.

Hydraulic flow direction alters impacts of AgNPs on pollutant removal and silver spatial distribution in vertical flow constructed wetlands.

This study investigated the effects of AgNPs on pollutant removals in constructed wetlands (CWs) with different flow patterns and spatial distributions of silver. Before exposure to AgNPs, upward flow constructed wetland (UCW) had better nitrogen removal than down-flow CW (DCW). And 0.5 mg/L AgNPs evidently inhibited nitrogen and phosphorus removal, including ammonia, nitrate, and TP (total phosphorus), with average effluent concentrations increasing by 70.83% of NH4+-N in UCW, 18.75% of TP in UCW, and 28.33% and 25.06% of NO3--N in DCW and UCW, respectively, while COD (chemical oxygen demand) was not affected. Moreover, presence of 2 mg/L AgNPs slightly inhibited organic compounds and NH4+-N removal in two systems during stage 4 (dosing 2 mg/L AgNPs). However, the response of NO3--N and TN removal to 2 mg/L AgNPs in two systems were different, and nitrogen concentrations in effluent at the end of stage 4 significantly increased in DCW. Addition of 2 mg/L AgNPs significantly affected TP removal in two systems. Two wetlands showed high removal efficiencies of about 98% on AgNPs, indicating that CWs could provide a feasible approach for ecological restoration of nanoparticles pollution. This study also found that AgNPs mainly accumulated in the upper layer with the Ag content of 17.55-20.26 mg/kg dry weight in sand layer and 7.25-10.85 mg/kg dry weight in gravel layer. Plant roots absorbed AgNPs, with Ag content at 50.80-101.40 mg/kg and bioconcentration factors 2.80-5.00. The obtained results showed that up-flow CWs had better performance and higher resistance to the exposure of AgNPs pollution, compared with down-flow CWs.

Engineered methanotrophic syntrophy in photogranule communities removes dissolved methane

The anaerobic treatment of wastewater leads to the loss of dissolved methane in the effluent of the treatment plant, especially when operated at low temperatures. The emission of this greenhouse gas may reduce or even offset the environmental gain from energy recovery through anaerobic treatment. We demonstrate here the removal and elimination of these comparably small methane concentrations using an ecologically engineered methanotrophic community harbored in oxygenic photogranules. We constructed a syntrophy between methanotrophs enriched from activated sludge and cyanobacteria residing in photogranules and maintained it over a two-month period in a continuously operated reactor. The novel community removed dissolved methane during stable reactor operation by on average 84.8±7.4% (±standard deviation) with an average effluent concentration of dissolved methane of 4.9±3.7 mg CH4∙l−1. The average methane removal rate was 26 mg CH4∙l−1∙d−1, with an observed combined biomass yield of 2.4 g VSS∙g CH4−1. The overall COD balance closed at around 91%. Small photogranules removed methane more efficiently than larger photogranule, likely because of a more favorable surface to volume ratio of the biomass. MiSeq amplicon sequencing of 16S and 23S rRNA revealed a potential syntrophic chain between methanotrophs, non-methanotrophic methylotrophs and filamentous cyanobacteria. The community composition between individual photogranules varied considerably, suggesting cross-feeding between photogranules of different community composition. Methanotrophic photogranules may be a viable option for dissolved methane removal as anaerobic effluent post-treatment.

Performance and microbial community dynamics relationship within a step-feed anoxic/oxic/anoxic/oxic process (SF-A/O/A/O) for coking wastewater treatment

A step-feed anoxic/oxic/anoxic/oxic (SF-A/O/A/O) was developed and successfully applied to full-scale coking wastewater treatment. The performance and microbial community were evaluated and systematically compared with the anoxic/oxic/oxic (A/O/O) process. SF-A/OA/O process exhibited efficient removal of COD, NH4+-N, TN, phenols, and cyanide with corresponding average effluent concentrations of 317.9, 1.8, 46.2, 1.1, and 0.2 mg·L−1, respectively. In particular, the TN removal efficiency of A/O/O process was only 7.8%, with an effluent concentration of 300.6 mg·L−1. Furthermore, polycyclic aromatic hydrocarbons with high molecular weight were the dominant compounds in raw coking wastewater, which were degraded to a greater extent in SF-A/OA/O. The abundance in Thiobacillus, SM1A02, and Thauera could be the main reason why SF-A/O/A/O was superior to A/O/O in treating TN. The microbial community structure of SF-A/O/A/O was similar among stages in system (P ≥ 0.05, Welch's t-test) and was less affected by environmental factors, which may have been one of the important factors in the system's strong stability.

A novel pilot-scale IFAS-MBR system with low aeration for municipal wastewater treatment: Linkages between nutrient removal and core functional microbiota

In this study, we proposed a novel IFAS-MBR with low aeration for the treatment of real municipal wastewater. With biocarriers packed in the anoxic tank, the pilot-scale IFAS-MBR operated with average dissolved oxygen concentrations of 0.56 mg/L in the oxic tank. Over 110 days of operation, highly efficient nutrient removal was achieved with the total nitrogen (TN) and phosphorus (TP) removal efficiencies of 78.1 ± 7.2% and 93.7 ± 5.8%, respectively. The average effluent concentrations of TN and TP reached 5.4 and 0.26 mg/L, respectively. Meanwhile, the removal efficiency of COD reached 95.3 ± 1.3% in the system, and the concentrations of COD decreased from 31.9 ± 3.7 (sludge supernatant) to 12.7 ± 1.6 mg/L (permeate) after membrane filtration. Microbial community analysis showed that Nitrosomonas (0.32%) and Nitrospira (1.85%) in activated sludge were the main drivers of the nitrification process, while various denitrifying bacteria in activated sludge and biofilms were responsible for nitrate reduction in the anoxic tank. Candidatus Accumulibacter (0.34%) and Dechloromonas (1.31%) primarily contributed to denitrifying phosphorus uptake in the anoxic tank. Furthermore, these organisms (i.e., core functional microbiota) exhibited stable levels over the entire operation. The highly enriched hydrolytic fermentation bacteria drove community succession, and the remarkable functional robustness of microbial communities in activated sludge and biofilms favored nutrient removal. Overall, the novel IFAS-MBR system provides an energy-efficient MBR alternative owing to its highly efficient performance and low operating costs enabled by low aeration rates and the absence of an external carbon source.

Effect of constructed wetland system on aquaculture wastewater by ecological treatment

In this study, an integrated ecological system was constructed to treat small scattered aquaculture wastewater in southern rural areas of China. The water outlet of 4 level wetlands was continuously monitored from July to December in 2017. Results showed the average concentrations of total nitrogen (TN), ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3-N), total phosphorus (TP) and chemical oxygen demand (COD) were 43.64mg/L, 17.53mg/L, 1.71mg/L, 1.66mg/L and 51.39mg/L in the average effluent concentration of grade I wetland, respectively, and 8.35mg/L, 4.42mg/L, 0.24mg/L, 0.26mg/L, 21.32mg/L in the average effluent concentration of grade IV wetland, respectively. The removal rates were 81%, 75%, 86%, 85% and 59% for TN, NH4+-N, NO3-N, TP and COD in the integrated ecological system, respectively. The effluents from the integrated ecological system met the requirements of “Discharge Standard of Pollutants for Livestock and Poultry Breeding” (GB 18596-2001) and achieved “Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant” (GB 18918-2002) the center two levels to discharge the standard. Obviously, the integrated ecological system could work efficiently in treating the rural scattered aquaculture wastewater, and also possess merits of low construction and operation costs and simple management method, which will be benefited to its application in the southern rural regions of China.

Phosphorus removal potential at sewage treatment plants in Bavaria – a case study

Controlling phosphorus emissions from sewage treatment plants is a key factor in preventing eutrophication of surface waters. Regarding surface waters in Germany, the orientation value for the "good ecological status" for total phosphorus (Ptotal) is set at 0.10 mg Ptotal/L. To achieve this value, a further reduction in the Ptotal emissions from sewage treatment plants (STPs) is required. The evaluation of 2,626 Bavarian STPs showed a high reduction potential of the Ptotal emissions in STPs treating more than 1,000 population equivalents (PE). To achieve the goal of improving the surface water quality as well as to investigate which option is most feasible for Bavaria, three alternative scenarios of tightening the discharge permits of Ptotal were considered. By these scenarios, a reduction of the Ptotal load by app. 35%-50% can be achieved. For example, to reduce 50% of the Ptotal load, the discharge permits should be set as follows: STPs from 1,000 to 10,000 PE should comply with 1.0 mg Ptotal/L, STPs >10,000 PE to 0.5 mg Ptotal/L. The required annualized specific capital investment and operating costs required to implement simultaneous precipitation are fluctuating between 2 and 5 €/(PE•y). In larger STPs, an average effluent concentration of 0.5 mg Ptotal/L can generally be achieved, if clarification is designed and operated in accordance with applied regulated designing standards.

Novel approach to improving wastewater treatment and sewage sludge combustion using pulverized coal-activated sludge.

Sewage and sludge are usually treated separately. Considering improving sludge treatment while improving sewage treatment is beneficial to the synergetic effect of sewage treatment and sludge treatment. The efficiency of pulverized coal-activated sludge (PAS) on contaminant removal, sludge calorific value, and combustion characteristic was investigated in contrast to conventional activated sludge (CAS) using the laboratory-scale sequencing batch reactor (SBR). Results indicated that the average chemical oxygen demand, ammonium nitrogen, total nitrogen, and total phosphorus removal efficiency of PAS were highest under a dosage of 0.4g/L, which were 98.56%, 94.22%, 68.60%, and 95.96%, respectively. The average effluent concentration satisfied the Level A discharge standard of pollutants for municipal wastewater treatment plants (GB18918-2002). The calorific value and maximum weight loss of PAS gradually increased adjusting the dosage of pulverized coal. At the pulverized coal dosage of 0.2g/L, the calorific value of PAS with 70% water content is 3,824.07kJ/kg, which can satisfy the requirement of self-maintained combustion. Overall, the pulverized coal can simultaneously improve the treatment of wastewater in SBR and promote the sludge combustion by increasing calorific value. Therefore, PAS system is an innovation based on improving the sewage treatment sludge combustion. PRACTITIONER POINTS: An innovative method to simultaneously improving wastewater treatment and sewage sludge combustion using pulverized coal-activated sludge was developed. The average COD, , TN, and TP removal efficiency of PAS-0.4 is best. The 70% moisture content sludge calorific values of 3,824.07kJ/kg in PAS-0.2 can satisfy the requirement of self-maintained combustion.

Characteristics of Nutrient Removal in a Pilot-scale A2/O with Mixture of Sludge Fermentation Liquor and Tail Water as External Carbon Source

To resolve the issue of sewage fluctuation and discontinuity in a rural district of China, a new operation mode of replenishing the mixture of fermentation liquor and tail water during the off-flow period was proposed, and the nutrient removal performance of a pilot-scale A2/O system with this operation mode was investigated. The results of beaker experiments found that the mixture of tail water and fermentation liquor at a ratio of 12:1 had better denitrification and phosphorus release/absorption characteristics than the raw water, and theoretically had the function of enhancing denitrification and phosphorus removal performances. The results of a 97 d pilot test showed that the removal efficiency of TN and TP was improved after the system was adjusted from the constant flow mode to this new operation mode, and the average removal rate of TN and TP increased from 69.27% and 86.94% to 73.34% and 89.94%, respectively. The corresponding average effluent concentration decreased from 15.77 mg·L-1 and 0.80 mg·L-1 to 13.76 mg·L-1 and 0.64 mg·L-1. The sequencing results of the 16S rRNA gene showed that this new operation mode was beneficial to the enrichment of five common hydrolytic acidizing bacteria genera, six phosphorus-accumulating organisms genera, and four denitrifying bacteria genera. This was also the main reason for the improved nutrient removal performance. According to the long-term monitoring of the characteristics of activated sludge, this new operating mode will degrade the sedimentation performance of activated sludge in the system, and the average SVI increased from 106 mL·g-1 to 131 mL·g-1. However, this degree of deterioration did not adversely affect the sludge activity and nutrients removal performance of the system, and there was no sludge bulking in the entire experiment. The results of this study have shown that the A2/O system can maintain and improve the performance of nutrients removal by replenishing the mixture of tail water and sludge fermentation liquor when the flow is cut off. This will provide new ideas for the design and operation of sewage treatment plants in rural areas in the future.

Decentralized grey and black water reuse by combining a vertical flow constructed wetland and membrane based potable water system: Full scale demonstration

Safe drinking water is not accessible in many rural and peri-urban areas. Decentralized wastewater treatment can be a sensible solution for communities of any size and/or demographic having a very small water cycle and could be used as a solution to provide potable water at more remote locations. In view of demonstrating decentralized production of potable water, a hybrid system combining a vertical flow constructed wetland (VFCW) and a membrane filtration system was designed and operated at a restaurant. The VFCW with an area of 60 m2 was constructed and operated for six months at a hydraulic loading rate of 0.05 to 0.08 m3. m−2.d-1 and achieved a removal of 84%, 97%, 92%, 42% and 24% for chemical oxygen demand (COD), biological oxygen demand (BOD), total suspended solids (TSS), total nitrogen (TN) and total phosphorus (TP) respectively, corresponding to mass loading rates of 9.6 gCOD. m−2.d−1, 7.9 gBOD. m−2.d−1, 4.7 gTSS. m−2.d−1, 1.5 gTN. m−2.d−1. Final (average) effluent concentrations were 7 mg.L−1, 1.6 mg.L−1, 4.7 mg.L−1, 1.5 mg N.L−1 and 1.5 mg P.L−1 for respectively COD, BOD5, TSS, TN and TP. The VFCW effluent was further treated using a combination of activated carbon, ultrafiltration, reverse osmosis and mixed bed ion exchange, remineralization as well as ultraviolet disinfection to produce potable water. This potable water met the legislative criteria and was used in the restaurant for drinking and cleaning purposes. As such, a sustainable decentralized potable water system with direct black water reuse was demonstrated at full-scale.

Occurrence and Removal of Veterinary Antibiotics in Livestock Wastewater Treatment Plants, South Korea

In this study, livestock wastewater treatment plants in South Korea were monitored to determine the characteristics of influent and effluent wastewater, containing four types of veterinary antibiotics (sulfamethazine, sulfathiazole, chlortetracycline, oxytetracycline), and the removal efficiencies of different treatment processes. Chlortetracycline had the highest average influent concentration (483.7 μg/L), followed by sulfamethazine (251.2 μg/L), sulfathiazole (230.8 μg/L) and oxytetracycline (25.7 μg/L), at five livestock wastewater treatment plants. Sulfathiazole had the highest average effluent concentration (28.2 μg/L), followed by sulfamethazine (20.8 μg/L) and chlortetracycline (11.5 μg/L), while no oxytetracycline was detected. For veterinary antibiotics in the wastewater, a removal efficiency of at least 90% was observed with five types of treatment processes, including a bio-ceramic sequencing batch reactor, liquid-phase flotation, membrane bioreactor, bioreactor plus ultrafiltration (BIOSUF) and bio best bacillus systems. Moreover, this study evaluated the removal efficiency via laboratory-scale experiments on the conventional contaminants, such as organic matter, nitrogen, phosphorus and veterinary antibiotics. This was done using the hydraulic retention time (HRT), under three temporal conditions (14 h, 18 h, 27 h), using the anaerobic–anoxic–oxic (A2O) process, in an attempt to assess the combined livestock wastewater treatment process where the livestock wastewater is treated until certain levels of water quality are achieved, and then the effluent is discharged to nearby sewage treatment plants for further treatment. The removal efficiencies of veterinary antibiotics, especially oxytetracycline and chlortetracycline, were 86.5–88.8% and 87.9–90.8%, respectively, exhibiting no significant differences under various HRT conditions. The removal efficiency of sulfamethazine was at least 20% higher at HRT = 27 h than at HRT = 14 h, indicating that sulfamethazine was efficiently removed in the A2O process with increased HRT. This study is expected to promote a comprehensive understanding of the behavior and removal of veterinary antibiotics in the livestock wastewater treatment plants of South Korea.

Treatment of wastewater containing linear alkylbenzene sulfonate by bacterial-microalgal biological turntable

Linear alkylbenzene sulfonate (LAS), which is widely used as detergent, is a common toxic pollutant in wastewater. Generally, biodegradation process is applied to remove LAS. However, the efficiency of traditional wastewater treatment cannot meet the growing demand. In this study, an improved biological turntable with a symbiotic system of bacteria and microalgae was primarily used to enhance the biodegradation efficiency of LAS from wastewater. The symbiotic system of bacteria and microalgae was mainly composed of Scenedesmus dimorphus and three LAS-degrading bacteria Plesiomonas sp. (L3, L7) and Pseudomonas sp. (H6). The average removal rate of LAS was up to 94.6%. The LAS concentration of the effluent of the system decreased by 81.7% after the bacterial-microalgae inoculation (the inoculation temperature was 25 oC; microalgae were inoculated at a concentration of 10% only at the start of the system; bacteria were continuously inoculated at 1‰ concentration). After bacterial-microalgae inoculation, the average effluent concentration of CODCr in the tertiary reaction tank was 24.3 mg/L, the average membrane effluent concentration was 15.8 mg/L, and the average removal rate was 90.5%. Compared with the control group without inoculation, the concentration of CODCr in the tertiary reaction tank and membrane effluent decreased by 55.7% and 46.4%. The denaturing gradient electrophoresis (DGGE) pattern analysis of the systemic flora showed that there were two dominant species of high LAS degrading bacteria. They were identified to belong to Plesiomonas sp. and Pseudomonas sp., respectively.

Removal performance of high hydraulic loading rate subsurface wastewater infiltration systems with added Si[sbnd]Al porous clay material and scrap iron filings

To enhance pollutant removal performance in the treatment of decentralized domestic sewage, a subsurface wastewater infiltration system (SWIS) with turfy soil was improved by adding SiAl porous clay material W (PCMW) and scrap iron filings. The permeability at different depths of the SWIS was improved. Under the conditions of 186.18 ± 34.82 mg/L COD, 25.84 ± 2.57 mg/L NH4+-N, 3.02 ± 0.91 mg/L NO3−-N, 33.87 ± 3.78 mg/L TN, 6.93 ± 1.21 mg/L TP, a 0.28 m3/m2·d hydraulic loading rate and 716 d operation time, the average effluent concentrations of COD, NH4+-N, NO3−-N, TN and TP were 31.28 ± 5.87 mg/L, 3.39 ± 1.42 mg/L, 3.71 ± 0.87 mg/L, 7.11 ± 0.97 mg/L and 0.24 ± 0.07 mg/L, respectively, and the TN removal efficiency increased by 20.7% compared with that of the control SWIS. According to the pollutant variations with depth, 76.79% COD, 80.96% NH4+-N and 95.35% TP were removed at a depth of 110 cm, after which their concentrations remained stable; the TN concentration decreased with depth and was quite different from that of control SWIS, NH4+-N in TN was removed at a depth of 0–90 cm, and NO3−-N in TN was removed at 90–170 cm depth. Moreover, both the number of nitrifying/denitrifying bacteria and nitrate/nitrite reductase activity reached their maximum at 90 cm depth. Adding PCMW and scrap iron filings to SWISs could be an ideal method to improve the performance and service life of SWISs.