Treatment Of Domestic Effluents Research Articles

Treatment of domestic effluents using sustainable biofilter methods

The discharge of effluents is a permanent environmental and sanitation concern. Efficient water management must include water treatment and reuse. It is therefore necessary to study treatment systems to improve their performance throughout the entire chain, from drinking water to wastewater or, more specifically, waste effluent. Currently, technologies using bio-filtration processes have proven to be an effective and low-cost method for treating industrial effluents and domestic sewage. In this study, a low-cost domestic sewage treatment system made up of biofilters and pipes was built on a bench model as a means of teaching practical classes, and its efficiency was also studied. The results showed that the equipment can be made from recyclable material and is low-cost, easy to detail technically and easy to handle and operate. The students involved can easily replicate the technology in their communities, thus spreading low-cost sanitation treatment technologies to low-income populations without access to conventional sanitation systems. The parameters pH, turbidity, chlorination, temperature, and electrical conductivity were all at acceptable levels for discharge into receiving bodies and domestic use.

Microbiological characterization of biofilm from different immobilization structures used in submersed aerobic biofilters in domestic effluent treatment at the city of Joinville, Brazil.

The objective of this work was to develop a polymeric structure for a biofiltration unit of domestic effluents through microbiological immobilization, capable of promoting the efficient removal of pollutants, meeting local/national Brazilian standards and/or legislation while providing low environmental impact on their production. Four different structures were tested, namely, polypropylene casings without filling material (TF1); polypropylene casings filled with expanded polystyrene grains (TF2); polypropylene casings, filled with polyurethane foam (TF3); and polypropylene casings, filled with polyvinyl chloride pellets (TF4). A flow of 0.216 m3 d-1 was applied to the system, and the biofilters operated in sequential batches with a hydraulic retention time of 6h. The efficiency potential of the four immobilization structures was verified regarding biochemical and chemical oxygen demand, total ammoniacal nitrogen and total phosphorus. Microbiological analysis of the formed biofilm, performed with the 16S library sequencing method, with amplification of the 16S rRNA V3 and V3-V4 genomic regions, showed a high diversity of microbiological colonization in the four immobilization structures, with better results and consequently greater community stability in TF2. It is recommended using the filter bed made up of unfilled casings, followed by the one filled with expanded polystyrene grains.

Textile and domestic effluent treatment via co-cultivation of Diplosphaera mucosa VSPA and Scenedesmus obliquus

The present research aimed to study the efficiency of two microalgae strains in treating textile and domestic effluent in co-cultivation mode. A newly isolated strain, Diplosphaera mucosa VSPA, and Scenedesmus obliquus were co-cultivated in the mixotrophic and heterotrophic modes in the effluents. Monoculture cultivation mode acted as a control. Co-cultivation was performed at an inoculation ratio of 01:04 (Diplosphaera:Scenedesmus) in a conventionally designed 10 L photobioreactor. The highest biomass concentration was achieved in mixotrophic co-cultivation mode, which was 8.87 ± 0.05 g/L in domestic effluent and 6.14 ± 0.03 g/L in textile effluent. Biomass productivity in co-cultivation mode was nearly 1.5–2 times higher than in mono-cultivation mode. The substrate removal efficiency was also higher in the mixotrophic co-cultivation mode. More than 90% of ammonium-nitrogen, chemical oxygen demand, and 80% of phosphate-phosphorus removal were obtained from both effluents. Microscopic and flow cytometry analysis revealed that the final biomass concentration contains more Diplosphaera culture. It was concluded that the co-cultivation strategy is better than mono-cultivation for treating high-strength industrial effluent. Also, the experimental results of the co-cultivation mode were verified and simulated via various growth and substrate removal models.

Sewage contamination assessment in an urbanized tropical estuary in Northeast Brazil using elemental, isotopic and molecular proxies

The Capibaribe Estuarine System (CES) is a tropical estuary located within a densely populated metropolitan region in the Brazilian Northeast, providing multiple ecosystem services including artisanal fisheries, tourism, and navigation. A significant load of domestic and industrial effluents is causing visible environmental degradation that needs to be characterized. This study evaluated the degree of contamination by domestic sewage and the relative contribution of organic carbon (OC) sources in sediments, measuring carbon-to-nitrogen atomic (C/N)a ratios, δ13C of OC, and linear alkylbenzene concentrations (LAB). The SIAR mixing model indicated that estuarine phytoplankton and sewage contribute 73% and 22% to OC, respectively, based on sedimentary (C/N)a ratios that varied from 8.5 to 13, and δ13C ranging from −25.21 to −21.63‰. This suggests that eutrophication of CES is triggered by sewage inflow. The CES was moderately contaminated by LAB, and the highest concentrations observed in the inner portion, from 287 to 1349 ng g−1 dry weight, suggests the retention of sewage. The mixing isotopic model indicated a significant dilution process of sewage-derived OC by estuarine phytoplankton. The lowest LAB in the lower estuary (317–320 ng g−1 dw) probably resulted from marine dilution. Principal component analysis demonstrated that mud regulates sedimentary OC content, and that the sewage plume regulates sedimentary LAB. High degradation of LAB isomers probably reflects the net heterotrophic condition of this system, also suggesting these compounds are introduced into CES partially degraded. Our results pointed out that degraded OM is a result of chronic and long-term sewage input. Considering the implications of sewage pollution to environmental and public health, there is an urgent need of better policies to improve domestic effluent treatment capacity, reducing contamination of estuarine environments.

PERFIL DOS PESCADORES RECREATIVOS NA LAGUNA DA JANSEN, SÃO LUÍS, ESTADO DO MARANHÃO

This study provided to analyze the profile of recreational fishermen who frequent Laguna da Jansen on the island of São Luís - MA, Eastern Amazon, because of the socio-economic importance of the activity as an important source of employment and income. Data were collected from June to August 2020 from semi-structured online interviews applied to the study’s target audience using the “snowball” method. 78 questionnaires were applied, of which 95% were men, aged between 26-35 years (35%), 40% with professional occupation in the private sector, and average monthly salary ranging from 1 to 3 minimum wages (47%). Most of the interviewees use: reel and spinning reels (31%), with artificial baits (54%) and landed fishing (37%). They have the snnoks Centropomus spp. (34%), the tarpon Megalops atlanticus (31%), and the ladyfish Elops saurus (15%) as target species. Recreational fishing in Laguna da Jansen has shown to be very promising, but it needs improvements in the local infrastructure, such as the construction of a fishing pier, kiosks with specific stores for fishing materials, and selling food products, cleaning, public lighting, and treatment of domestic effluents and improving the system for opening and closing the gates, optimizing the flow of water exchange, and minimizing eutrophication due to the accumulation of organic matter and other organic and inorganic compounds.

Surfactants in sediment of Itanhaém Estuary, São Paulo, Brazil

AbstractThis study investigated surfactant levels in the sediment of Itanhaém Estuary through colorimetric methods with methylene blue active substances (MBAS). Samples were collected with a Van Veen bottom sampler at eight sampling points during autumn, winter, and spring of 2015. The results demonstrate growing detergent deposition in the sediment of the estuary. Surfactant concentration was higher (16.18 μg MBAS g−1) around the sewage treatment plant (STP) than in the estuary in autumn, after the vacation/summer season when the population of the city had increased due to tourism. There was a significant (p < 0.05) reduction in detergent concentration (to 14.94 μg MBAS g−1) in winter, after school vacation, while in spring the surfactants concentration for the STP was high only for the sampling points nearer the ocean. Surfactant concentrations differed significantly among sampling points (p < 0.05), with them being higher at those closer to the STP. Enrichment with high loads from anthropogenic sources associated with urbanization and tourism was responsible for the greater surfactant concentrations in areas near the STP. In conclusion, more efficient treatment of domestic effluent of the city of Itanhaém is needed, as is the control of clandestine discharge into the river since the accumulation of detergents in sediment can have harmful effects on aquatic life.

Post-treatment of Anaerobic Reactor Effluent by Double Filtration with Gravel and Clinoptilolite and Ozone Disinfection

Anaerobic reactors are an excellent alternative in the treatment of domestic effluents. However, this system presents the disadvantage of requiring post-treatment. Many technologies have been studied and rapid filtration systems have proven to be a viable alternative for the post-treatment of anaerobic reactor effluents. This study evaluates the efficacy of an anaerobic reactor effluent post-treatment system using double filtration (DF), which consists of an upward gravel filter and a downward filter of clinoptilolite, and disinfection by ozonation. The system was evaluated using physicochemical and microbiological parameters. The lowest ozone dose (0.4 mg L -1 ) indicated possible oxidation of fractions of biodegradable organic matter with BOD removals above 95%. Higher ozone concentrations (5.0 and 7.0 mg L -1 ) improved COD removal and total nitrogen removal. Regarding microbiological parameters, over 87% E. coli and 89% total coliforms could be removed only with the use of DF, while total inactivation was observed using doses above 5.0 mg L -1 ozone. The results showed that following the proposed treatment, the effluent treated with the DF/Ozonation combination meets the guidelines for reuse in toilets, irrigation of orchards, cereals, pastures, and other crops through runoff or by punctual irrigation system according to the NBR 13969/97. According to these results, DF using clinoptilolite followed by ozonation is a promising technology for the anaerobic reactor effluent post-treatment. DOI: http://dx.doi.org/10.17807/orbital.v13i4.1617

The effects of anaerobic reactor post-treatments by rapid filtration systems and conventional techniques.

Although anaerobic reactors are an excellent alternative in the treatment of domestic effluents, they have the disadvantage of requiring post-treatment. Many technologies have been studied and, recently, rapid filtration systems have been presented as a viable alternative for post-treatment. This work compared post-treatment techniques for anaerobic upflow sludge blanket (UASB) reactors by rapid filtration systems (double filtration (DF); triple filtration with clinoptilolite (TFc); and triple filtration with activated carbon (TFac)) to conventional systems (facultative pond (FP); biological filter (BF); biological filter with recirculation and decantation (BFD)), verifying their potential for improvement of the final effluent quality. The UASB effluent post-treatments by FP, BF, BFD, DF, TFc, and TFac were evaluated. The removal of turbidity in both BFD and FP post-treatments was below 75%. The DF, TFc, and TFac treatments showed over 99% removal of the same parameters. COD removal in the FP, BF, and BFD post-treatments was over 10%, while in the DF, TFc, and TFac treatments, it was over 80%. The greatest total phosphorus removal was observed in TFc and TFac, whose values were over 99%. The best removal of ammoniacal nitrogen, 99% was observed in the TFc treatment. Regarding Al, Cd, Cr, Cu, Mn, Ni, Pb, and Zn removal, all rapid filtration systems showed better performance when compared to conventional systems. The DF, TFc, and TFac systems showed over 90% removal of most metals evaluated, while the FP and BF treatments presented values below 50% for most metals, and in the BFD system, the removal values were below 80% for most metals. The results indicate that rapid filtration systems were better at removing all evaluated parameters when compared to conventional systems.

Zeolitas nativas en el tratamiento de agua residual doméstica

En esta investigación zeolitas de río y de cerro fueron evaluadas para ver su potencial en el tratamiento de aguas residuales. En primer lugar, se diseñó y construyó un sistema experimental de tres biorreactores de lecho fijo de flujo ascendente (BLFFA) con una altura de 1.5 metros y diámetro de cuatro pulgadas, seguidamente se evaluó el potencial de las zeolitas nativas y una testigo comercial en el tratamiento de aguas residuales. Se arrancaron los BLFFA con un diseño factorial 3 x 3, operando con zeolita de río, zeolita de cerro y zeolita comercial (control), todas con partículas de ¼ de pulgada, utilizando tres diferentes alturas de lecho (0.75, 0.90 y 1.10 m) y tres tiempos de retención hidráulica (6, 12 y 24 horas). Se evaluaron las variables de respuesta mediante un análisis de varianza multifactorial y para discriminar entre las medias se empleó el método de diferencia mínima significativa (LSD) de Fisher (p < 0.05, 95 % de confianza). La zeolita de cerró presentó (promedio, N = 10) las mejores características fisicoquímicas con densidad real y aparente de 2700 y 1470 kg/m3 respectivamente, peso específico de 2240 kg/m3, porosidad de 62 %, absorción de 15.20 %, solubilidad en ácido clorhídrico de 29.96 %, pH de 7.4 y conductividad eléctrica de 70 mS/cm. Al agua residual con las que se desarrollaron los tratamientos se le aplicó previo al experimento un tratamiento primario (rejilla, desarenador, desnatador y fosa séptica) y presentó valores (promedio, N = 9) de temperatura de 25.26 °C, pH de 8.63, sólidos disueltos totales con 950.50 mg/L, color de 1305.10 UC, turbiedad 96.37 UNT y demanda química de oxígeno de 373 mg/L. De las zeolitas evaluadas (N = 81) en el BLFFA, la que presentó el mejor tratamiento fue la zeolita de cerro operando con una altura de lecho de 0.9 m y con 24 horas de tiempo de retención hidráulica; obtuvo las mejores eficiencias de remoción con 71.42 % en sólidos disueltos totales, 84.34 % para turbiedad, 96.33 % para color y 97.28 % para la demanda química de oxígeno. La altura óptima en los BLFFA fue 0.9 m, factor importante de evaluar, ya que a mayor altura se aumentan los costos y las eficiencias no son relevantes para justificar la inversión y a menor altura cae el rendimiento en calidad del agua tratada. En conclusión, las zeolitas nativas cuentan con propiedades idóneas para ser utilizadas en el tratamiento de agua residual doméstica y podemos recomendar la implementación de los BLFFA en el tratamiento secundario de efluentes domésticos en sistemas descentralizados del sureste de México como una alternativa viable en el tratamiento de sus aguas residuales domésticas.

Evaluation of the Efficiency of a Septic Tank Combined with Anaerobic Filter, Filled with Plastic Residue, Including a Root Zone

Considering the damages resulting from the dumping of waste in natura in the bodies of water and soil, an alternative system of treatment of domestic effluent with septic tank and an anaerobic filter was installed, following a root zone. The evaluation of the efficiency of the system was based on analyzes of the physical, chemical, biological variables and ecotoxicological tests (toxicity tests with Ceriodaphnia dubia). The conductivity values decreased after treatment (83.4%), from 3380 to 561 µS cm-1. The average efficiency of removal of organic matter was 88.75% and there was a significant decrease in BOD. The removal of phosphorus was 97.68% and nitrogen was 94.7%. The toxicity tests determined an LC50 = 1.70% for the raw effluent and in the treated effluent, an LC50 = 16.63%. The system achieved good efficiency in the reduction of all analyzed parameters. The use of a plastic residue as a filter element has proved quite feasible.

Electro-oxycoagulation Efficiency for the Treatment of Domestic Effluents

Although environment protection efforts worldwide, the chemistry and biological contamination of waters represents an important challenge to be overcome, especially regarding its contamination by domestic wastewater effluents. In this context, this research presented an analysis by using an innovative wastewater treatment system for domestic effluents based on the electro-oxycoagulation approach implanted in wastewater treatment station located at Palma Sola, Santa Catarina, Brazil. We evaluated samples from domestic effluent (before and after treatment), fountain water, and river water collected from the municipality water system, as well as investigated the residual compound yielded by wastewater treatment. In these samples, we performed physicochemical analysis, investigation of viable helminth eggs, and toxicity and microbiological measurements before and after the treatment. Further, the levels of contaminant metals by X-ray fluorescence-based technique were analyzed. Results show an improvement in the quality of treated water, as demonstrated by microbiological, physicochemical, toxicity, and metal analysis of effluent after treatment. After treatment, river water and fountain water levels of metals in accordance with the maximum limits allowed by Brazilian regulatory agencies. Analysis of residual compound indicated that the workers that handle the residue were not contaminated with the identified metals. Thus, the electro-oxycoagulation-based method demonstrated high efficiency for the treatment of domestic effluents and further prevents contamination of the rivers by the released effluent without treatment.

A comparison of different scenarios for on-site reuse of blackwater and kitchen waste using the life cycle assessment methodology

Decentralized systems for treatment of domestic effluents have been suggested as a sustainable alternative for situations where conventional sanitation has not yet been established. This study compares three possible scenarios for the destination of separated blackwater (BW) and kitchen waste (KW), being: co-digestion of both (BW&KW) in loco with subsequent reuse of sub-products like nutrients and water (scenario 1); discharge of BW into a septic-tank and composting of the KW (scenario 2) and discharge of the BW into a septic-tank and of the KW at a solid waste disposal (scenario 3, actually the most common situation in large part of Brazil). In order to compare the scenarios, the use of equivalent amounts of water and fertilizer was considered in scenarios 2 (septic-tank and composting) and 3 (septic-tank and landfill), in order to maintain functional equivalence with that of scenario 1 (co-digestion and reuse). In scenario 1, treatment of the organic waste in an Upflow Anaerobic Sludge Blanket (UASB) reactor, for a period of 6 (scenario 1A) or 12 days (scenario 1B), with effluent recycling, was considered. In order to verify the effect of the use of energy in scenario 1 and to verify the effect of the degree of treatment realized in scenarios 2 and 3, a sensitivity analysis was realized for the parameters energy use and COD removal. The management of the sub-products in scenario 1 resulted in emission gains, when compared to scenarios 2 and 3, where the need to include amounts of water and fertilizer, to obtain functional equivalence, increased the environmental impacts associated to these scenarios. However the energy consumption increased the impact levels in scenario 1 and, overall, scenario 2 (septic-tank and composting), obtained the lowest impact scores, presenting the most advantageous scenario, among the three scenarios studied, from an environmental point of view, considering the restrictions as defined here, followed by scenarios 3 (septic-tank and landfill), 1A (6-day co-digestion and reuse) and 1B (12-day co-digestion and reuse). After the sensitivity analysis the influence of energy consumption on the impact categories for scenario 1 became evident, whereas, on the other hand, the degree of pollution removal from the blackwater did not change the overall results, making thus minimizing energy consumption during treatment more relevant than improving pollutant removal, in order to minimize the environmental impacts.

A structural equation model to predict macroinvertebrate-based ecological status in catchments influenced by anthropogenic pressures

A Partial Least Squares-Path Model (PLS-PM) was developed for the Ave River Basin (North of Portugal), and the results used in a scenario analysis. The data for PLS-PM comprised a set of anthropogenic pressures, water quality parameters, and a macroinvertebrate-based biodiversity index (IPtIN) used to assess the ecological status of streams. These groups of measured parameters (called latent variables) were given the names “Pressures”, “Contamination” and “Ecological Integrity”. Besides, latent variables were connected through path coefficients representing potential causal effects among them. In a large portion of Ave the ecological status of streams is currently bad or poor. Nitrate and coliforms were the most weighted measured variables of latent variable “Contamination”, with w ≈ 0.7 and w ≈ 0.2, respectively. The highest “Pressures” weights were ascribed to livestock farming (0.7) and population density (0.4). The connections “Pressures”—“Contamination” and “Contamination” — “Ecological Integrity” exposed a sequence of direct negative effects between the three variables, expressed in the corresponding path coefficients (pc = 0.87 and pc = −1.11). Paradoxically, a direct negative effect of “Pressures” over “Ecological Integrity” was absent (pc = 0.29). Therefore, the poor ecological status of local stream waters might not be directly related to the presence of potentially threatening contaminant sources (the “Pressures”), but to ineffective monitoring of livestock farming and wastewater treatment activities that potentiate (accidental) releases of contaminants into the streams. The lack of a direct link “Pressures” — “Ecological Integrity” supported the results of pressure change versus IPtIN change scenarios. Regardless of some significant reductions of anthropogenic activity and population density until 2027, announced by the Portuguese Environmental Agency, the scenarios could not predict improvement of ecological status beyond the “moderate” category. The study recommendations were therefore to prevent contamination through proper implementation and monitoring of existing watershed management plans. The adequate treatment of domestic effluents and the control of livestock farming residues are urgent.

TRATAMENTO DE ESGOTO DOMÉSTICO A PARTIR DO SISTEMA LEITO DE RAÍZES: EXPERIÊNCIA EM UMA PEQUENA COMUNIDADE RURAL DO SEMIÁRIDO BRASILEIRO.

O presente artigo aborda de forma sucinta a necessidade do manejo racional dos recursos hídricos e manejo ecológico da água no Semiárido Brasileiro, a partir da experiência de uma atividade extensionista na Escola Família Agrícola de Colônia, Itaetê-BA (EFACI), com o objetivo principal de realizar a instalação e operação de uma unidade experimental de tratamento de efluentes domésticos, por meio da técnica leito de raízes. Nesta etapa da pesquisa procedeu-se metodologicamente a execução de oficinas de capacitação com enfoque no planejamento ambiental participativo, manejo da água e do solo, bem como o tratamento de águas servidas, trabalhos de campo, com intuito de apresentar/compartilhar conteúdos técnicos e proporcionar a integração destes conhecimentos científicos com os saberes tradicionais da comunidade.

Long-term, low technicality sewage sludge amendment and irrigation with treated wastewater under Mediterranean climate: impact on agronomical soil quality.

We evaluated the agronomic quality of loam to clay-loam soils from a Mediterranean area, which have been submitted for more than 10years to irregular and poorly controlled treated wastewater (TWW) irrigation and sewage sludge (SS) amendment, both TWW and SS issuing from a domestic effluent treatment plant. A soil was submitted to SS amendment only, another to TWW irrigation only, another to both treatments, and another was not submitted to any of these treatments. We found that the agronomic quality of the treated soils has not decreased. In treated soils, it was observed a slight increase of pH, an increase of the cation exchange capacity, and no change of either salinity or electrical conductivity. Sodium adsorption ratio and exchangeable sodium percentage remained satisfactory, below 13 and 15, respectively, and no infiltration problems were observed, indicating that rainwater percolation was sufficient to leach the salt brought by SS or TWW. The soil organic matter (SOM) increased in all SS-amended and/or TWW-irrigated soils, the increase being higher in SS-amended soils. The SOM kept a satisfactory C/N ratio, lower than 15; the SUVA (Specific UV Absorbance)and E2/E3 index showed normal characteristics of the water-extracted organic matter (WEOC). Both SS amendment and TWW irrigation brought high amounts of nutrients in the considered soils and increased the nutrients disponibility, especially regarding K and P, as shown by the nutrient concentrations in the soil water extracts. The pH increase does not seem to be a problem for the bioavailability of trace elements, at least regarding Cu, Zn, Co, and Fe. Complementary studies should be undertaken for Ni. These observations highlight the potential agronomical benefits of application of wastewater and sewage sludge, even without great technicality, the better results being obtained using both SS amendment and TWW irrigation.

Application of Activated Carbon in the Treatment of Domestic Effluent: A Comparative Analysis

Application of Activated Carbon in the Treatment of Domestic Effluent: A Comparative Analysis

Assessing anthropogenic impacts on riverine ecosystems using nested partial least squares regression.

The results of three Partial Least Squares (PLS) regression models were used to gain a holistic view on the consequences of natural processes and anthropogenic pressures for water quality degradation and biodiversity decline in a multi-use watershed. The processes were soil erosion and wildfire risk; the pressures comprised land use conflicts, leachates from domestic and industrial waste, arable farming intensity and livestock density. Water quality was characterized for concentrations of nutrients (nitrate, phosphate), oxygen demands (Biochemical Oxygen Demand - BOD5, Chemical Oxygen Demand - COD) and various metals (e.g., As, Cr). Ecological integrity was assessed by the recently developed MELI (Multiple Ecological Level Index). In total, 18 variables were processed in the regression models. Two models were called "nested models" because they dealt with initial (pressures), intermediate (water quality) and final (MELI) environmental descriptors, used as dependent (MELI, quality) or independent (quality, pressures) variables. The third was called "bypass model" because it dealt solely with initial and final descriptors. Overall, the results of PLS regression linked the ineffective treatment of domestic sewage to water quality and ecological integrity declines in the studied watershed. Put another way, all models recurrently affirmed the major role of local factors, meaning of point source pollution, in determining the quality of stream water and the integrity of freshwater ecosystems. Sources of diffuse pollution were accounted for as contributing factors in the PLS regressions, but their influence was scarcely perceptible in the results. The poor treatment of domestic effluents is a public concern. In their strategic plans for mitigating this problem in the forthcoming years, administrative authorities are concentrated on management initiatives to improve the quality of provided services, instead of considering the construction of new wastewater treatment plants.

Behavior of pharmaceuticals in UV photoreactors fed with sewage treated by anaerobic/aerobic system

ABSTRACTThis work has assessed the seasonal changes and the dynamics in the concentration of six pharmaceutical compounds during photolysis as a tertiary treatment of sewage previously treated by an anaerobic/aerobic system comprising a UASB (Upflow Anaerobic Sludge Blanket) reactor and a trickling filter (TF). The target compounds were four antibiotics (ciprofloxacin (CPF), clindamycin (CLM), sulfamethoxazole (SMX), and trimetoprim), one β-blocker (atenolol), and one anti-inflammatory (diclofenac (DCF)). Six hydraulic retention times (HRTs) were evaluated (5, 10, 20, 40, 80, and 160 min) with the intent of varying the ultraviolet C (UVC) radiation doses applied to the effluent from biological treatment containing the target contaminants. The concentrations of pharmaceutical compounds in the effluent of the UASB/TF system were in agreement with the concentration levels reported in the literature. Aside from DCF, the seasonality seems to be a preponderant characteristic regarding the pharmaceutical concentration found in the effluent of biological treatment systems. The radiation dose of 117 mJ cm−2 seemed to be most suited for the photolysis application to tertiary treatment of domestic effluents. It was observed that lower UVC doses led to deconjugation of pharmaceuticals, which can result in increased concentrations of target pollutants in the photoreactor effluent.

Formation and properties of sediments in constructed wetlands for treatment of domestic wastewater

Sediments formation and biogeochemical properties were studied in an experimental constructed wetland site in Ukraine (“Bioplato”) for treatment of domestic effluents. The wetland, with a capacity of 50 m3 d− 1 of wastewater, consists of vertical and horizontal filtrations units with fine gravel, middle and coarse sand, a subsurface flow unit with natural wetland soil applied, and a septic tank and sludge-drying field. Macrophytes, reed (Phragmites australis), cattail (Typha latifolia) and a number of sedge species (Carex spp.) were planted in the area and dominate the average cover of 85–90%. Treatment efficiency for BOD5 and suspended solids was 93–96%, for COD – 82%, for nutrients – 27–50%, and for pathogenic microorganisms 99.3–99.6%. Sludge was sampled at each unit followed by standard laboratory analyses of its main characteristics: total organic carbon (TOC), total nutrients (N, P), contents of trace elements, abundance of pathogenic microorganisms, and general toxicity. Results confirmed that the top layer of sludge from each unit of wetland could be used as a source of fertilizers for grain and leguminous crops.

Hydrodynamic characterisation of an airlift reactor for domestic wastewater treatment

This study evaluates the hydrodynamic and mass-transfer behaviour of a 20-L airlift photobioreactor, employed for secondary wastewater treatment of domestic effluent. Gas hold-up (e), as well as the volumetric mass transfer coefficient (k L a) was assessed as a function of superficial gas velocity (Ug) for both bi- and triphasic systems. In the experimental range of Ug investigated, the maximum k L a and e obtained were in the order of 0.0074 s −1 and 0.035 for water/ air system and 0.0097 s −1 and 0.026 for triphasic system respectively. The results indicate that this PBR is a good candidate for wastewater treatment, with lower power costs than other types of biological reactors.