Vertical-flow Filters Research Articles

Performance Evaluation of Two Series Vertical Flow Filters for Wastewater Treatment: A Case Study of the Prototype Installed at Gaston Berger University, Saint-Louis, Senegal

Performance Evaluation of Two Series Vertical Flow Filters for Wastewater Treatment: A Case Study of the Prototype Installed at Gaston Berger University, Saint-Louis, Senegal

The effect of synthetic silver nanoparticles on the antibiotic resistome and the removal efficiency of antibiotic resistance genes in a hybrid filter system treating municipal wastewater

Engineered nanoparticles, including silver nanoparticles (AgNPs), are released into the environment mainly through wastewater treatment systems. Knowledge of the impact of AgNPs on the abundance and removal efficiency of antibiotic resistance genes (ARGs) in wastewater treatment facilities, including constructed wetlands (CWs), is essential in the context of public health. This study evaluated the effect of increased (100-fold) collargol (protein-coated AgNPs) and ionic Ag+ in municipal wastewater on the structure, abundance, and removal efficiency of the antibiotic resistome, integron-integrase genes, and pathogens in a hybrid CW using quantitative PCR and metagenomic approaches. The abundance of ARGs in wastewater and the removal efficiency of ARGs in the hybrid system were significantly affected by higher Ag concentrations, especially with collargol treatment, resulting in an elevated ARG discharge of system effluent into the environment. The accumulated Ag in the filters had a more profound effect on the absolute and relative abundance of ARGs in the treated water than the Ag content in the water. This study recorded significantly enhanced relative abundance values for tetracycline (tetA, tetC, tetQ), sulfonamide (sul1, sul2), and aminoglycoside (aadA) resistance genes, which are frequently found on mobile genetic elements in collargol- and, to a lesser extent, AgNO3-treated subsystems. Elevated plasmid and integron-integrase gene levels, especially intI1, in response to collargol presence indicated the substantial role of AgNPs in promoting horizontal gene transfer in the treatment system. The pathogenic segment of the prokaryotic community was similar to a typical sewage community, and strong correlations between pathogen and ARG proportions were recorded in vertical subsurface flow filters. Furthermore, the proportion of Salmonella enterica was positively related to the Ag content in these filter effluents. The effect of AgNPs on the nature and characteristics of prominent resistance genes carried by mobile genetic elements in CWs requires further investigation.

Use of Shredded Recycled Plastic as Filter Bed Packing in a Vertical Flow Filter for Onsite Wastewater Treatment Plants: Preliminary Findings

Household wastewater is a problem, especially in areas with a dispersed settlement where there is no wastewater collection system or wastewater treatment plant. In this case, it is necessary to build a local or onsite wastewater treatment plant. This paper is an attempt to analyse the possibility of using recycled shredded ABS plastic (acrylonitrile butadiene styrene) as packing media in an experimental vertical flow filter for use in on-site wastewater treatment plants. Studies have shown that shredded recycled ABS is a promising filtration material that has several features important in the treatment process, like a large surface area, high mechanical strength and chemical inertness. The system was operated with a hydraulic load of 50 dm3/m2 (3 months). BOD5 (biochemical oxygen demand), COD (chemical oxygen demand), and total suspended solids (TSS) reduction efficiency in the primary effluent was high; 94.4%, 77.8%, and 92.8%, respectively.

Impact of synthetic silver nanoparticles on the biofilm microbial communities and wastewater treatment efficiency in experimental hybrid filter system treating municipal wastewater

Silver nanoparticles (AgNPs) threaten human and ecosystem health, and are among the most widely used engineered nanomaterials that reach wastewater during production, usage, and disposal phases. This study evaluated the effect of a 100-fold increase in collargol (protein-coated AgNP) and Ag+ ions concentrations in municipal wastewater on the microbial community composition of the filter material biofilms (FMB) and the purification efficiency of the hybrid treatment system consisting of vertical (VF) and horizontal (HF) subsurface flow filters. We found that increased amounts of collargol and AgNO3 in wastewater had a modest effect on the prokaryotic community composition in FMB and did not significantly affect the performance of the studied system. Regardless of how Ag was introduced, 99.9% of it was removed by the system. AgNPs and AgNO3 concentrations did not significantly affect the purification efficiency of the system. AgNO3 induced a higher increase in the genetic potential of certain Ag resistance mechanisms in VFs than collargol; however, the increase in Ag resistance potential was similar for both substances in HF. Hence, the microbial community composition in biofilms of vertical and horizontal flow filters is largely resistant, resilient, or functionally redundant in response to AgNPs addition in the form of collargol.

Performance Evaluation of Laboratory Scale Vegetated Vermifilter for Domestic Wastewater

Abstract: Locally as well as globally, the Collection and treatment of wastewater are seen to have an impact on the environment and economy in one way or the other. Designing a system that minimizes this effect to the best possible scenario is of paramount importance, adding to greater sustainability in terms of economic, environmental, and social terms. The solutions such as on-site treatment of wastewater, local recycling, and reuse of resources contained in domestic wastewater (predominantly water itself) can be best summed up as Decentralized treatment of sewage which appears to be a coherent solution to address sustainability. Vermifiltration is a low-cost aerobic decentralized wastewater treatment option. Two lab-scale vertical flow filters are designed in this project, with both being assisted by Canna indica (MAVF), but only one introduced with Eisenia fetida. The experimental phase continued for 5 weeks with a hydraulic loading rate of 0.14 m3 m -2 day-1 with an acclimatization period of 15 days. The results depicted that MAVF has a better organic degradation capacity than the one without earthworms alone. The quality of wastewater is determined by Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD) to a great extent. Removal efficiencies of COD were 67 % for MAVF and 55 % for MAF, while for BOD, it was 80 % for MAVF and 69 % for MAF, respectively. The BOD and COD tests were assisted by other parameters like pH, and turbidity. Keywords: Domestic wastewater, Decentralized treatment, Aerobic treatment, Macrophyte Assisted Vermifilter (MAVF), Macrophyte Assisted Filter (MAF), Sustainability, Low-Cost Treatment, Canna Indica, Eisenia Fetida

Efficiency of saturated vertical-flow filters planted with Panicum maximum reeds for passive wastewater treatment

ABSTRACT A vertical-flow unit containing four filters filled with shale was used to study the removal of phosphorous, nitrogen and organic matter of an urban residual wastewater during a period of 90 days. The influence of both the shale granulometry and the plant density of Panicum Maximum were studied. The decrease of the shale granulometry led to a significant improvement of all the measured parameters, while the presence of plants did only influence the phosphate retention with a lower extent. By comparing the results to previous studies, we hypothesised that the effect of the root system of Panicum maximum would be different depending on the size and the depth of the reactors. For practical application, adjusting the material granulometry was proposed to be the most important parameter for improving the filtration efficiency. Concomitantly, adjusting the plant density helps to control the clogging percentage of the filters.

Modeling and optimization of wastewater treatment, from the Ain Chock Faculty in Morocco, using the vertical flow filter filled with pozzolana

Modeling and optimization of wastewater treatment, from the Ain Chock Faculty in Morocco, using the vertical flow filter filled with pozzolana

Domestic Wastewater Treatment by Vertical-Flow Filter Grown with Juncus Maritimus in Arid Region

This study aims to experimentally investigate the performance ofJuncus maritimusspecies in removing pollutants from domestic wastewater under arid conditions. The experiment was carried out for three month and several physicochemical and organic parameters were monitored. Results showed a good quality of filtered waters reflecting the high efficiency of vertical-flow filters. The presence of Juncus maritimus species promotes significantly the nitrogen elimination and augments the dissolved oxygen content at the outlet.It was also found that the planted filter provides small improvements in removing BOD5, TSS and TP removal for the three pollutants. The mean removal rate obtained withJuncus maritimusfilter was 91.05 % for BOD5, 86.67 % for TSS, 78.45 % for Ntot, and 95.14 % for TP. Microbial activity, uptake by plants, adsorption and physical sedimentation are the main mechanisms of limiting the contaminants rates in the vegetated vertical-flow filter.

Combined Vertical-Horizontal Flow Biochar Filter for Onsite Wastewater Treatment—Removal of Organic Matter, Nitrogen and Pathogens

This study investigated the performance of a combined vertical-horizontal flow biochar filter (VFF-HFF) system in terms of organic matter, total nitrogen (Tot-N), Escherichia coli and Salmonella removal and explored the effects of hydraulic loading rate (HLR) on pollutant removal. The combined VFF-HFF system used biochar as the filter medium and comprised two stacked sections: (i) an aerobic vertical flow filter (VFF) in which the wastewater percolated through the biochar medium in unsaturated mode and (ii) a horizontal flow filter (HFF), in which the biochar was saturated with water and had limited access to air, to enable anaerobic conditions and enhance the denitrification process. The system was tested over 126 weeks using real wastewater applied at different HLR (23, 31, 39 L m−2 day−1). The results showed that long-term removal of organic matter in the entire system was 93 ± 3%, with most (87 ± 5%) occurring in the VFF. For Tot-N, the long-term removal was 71 ± 12%, with increasing trends for nitrification in the VFF and denitrification in the HFF. Mean long-term nitrification efficiency in the VFF was 65 ± 15% and mean long-term denitrification efficiency in the HFF 49 ± 14%. Increasing HLR from 23 to 31 L m−2 day−1 increased the nitrification efficiency from 42 to 61%. Increasing the HLR further to 39 L m−2 day−1 decreased the denitrification efficiency from 45 to 25%. HLR had no significant effects on VFF and HFF performance in terms of E. coli and Salmonella removal, although the VFF achieved a 1.09–2.1 log10 unit reduction and the HFF achieved a 2.48–3.39 log10 unit reduction. Thus, long-term performance, i.e., removal of pollutants measured during the last 52 weeks of the experiment, was satisfactory in terms of organic matter and nitrogen removal, with no signs of clogging, indicating good robustness of the combined VFF-HFF biochar filter system.

Influence of design parameters on the treatment performance of VF wetlands - a simulation study.

The main approach for designing vertical flow (VF) treatment wetlands is based on areal requirements ranging from 2 to 4 m2 per person equivalent (PE). Other design parameters are the granularity of the filter material, filter depth, hydraulic and organic loading rates, loading intervals, amount of single doses as well as the number of openings in the distribution pipes. The influence of these parameters is investigated by running simulations using the HYDRUS Wetland Module for three VF wetlands with different granularity of the filter material (0.06-4 mm, 1-4 mm, and 4-8 mm, respectively). For each VF wetland, simulations are carried out at different temperatures for different organic loading rates, loading intervals and number of distribution points. Using coarser filter material results in reduced removal of pollutants and higher effluent concentrations if VF wetlands are operated under the same conditions. However, the treatment efficiency can be increased by applying more loadings and/or a higher density of the distribution network. For finer filter material, longer loading intervals are suggested to guarantee sufficient aeration of the VF filter between successive loadings.

Waste assessment decision support systems used for domestic sewage treatment

The paper discusses the use of Decision Support Systems (artificial neural networks analysis preceded by Principal Component Analysis) for the assessment of domestic sewage filtration effectiveness with four types of waste serving as filling materials in vertical flow filters. The study analyzed the effectiveness of pollution removal from wastewater by mechanically shredded waste in the form of PET flakes, polyurethane foam trims, shredded rubber tires and wadding. The organic compounds (CODcr, BOD5) removal, suspended solids, biogenic compounds (N-NH4+, PO43−) and oxygen saturation changing compared with reference sand filling was analyzed. The paper presents the proposal for the use of artificial neural networks as a tool to support decision making on the selection of waste material, filling vertical filters cooperating with the septic tank. An analysis of the functioning of the trained neural network was performed, comparing its responses with the reduction values obtained for individual fillings under changing hydraulic conditions. Generally good agreement between the predictions of the neural model and the reduction values was obtained for the MLP 11-7-2 network.

Data clustering analysis in the assessment of wastes using in the sewage filtration

Abstract The paper discusses the use of multiclustering statistical analysis in the assessment of domestic wastewater filtration effectiveness. Calculations included data collected over four months of experiments with using waste as filling material of vertical flow filters for domestic sewage treatment. The effectiveness of pollutants removal was analysed in case of mechanically shredded waste in the form of PET flakes, PUR foam trims, shredded rubber tires and wadding. The organic compounds (CODcr, BOD5) removal, suspend solids, biogens (as NH4+, PO43−ions) and oxygen saturation changing compared with sand filling was analysed. Multiclustering statistical analysis allowed to divide pollutants removal efficiency of analysed materials into 3 clusters, depending on the hydraulic loading. The first group consisted in quality parameters of treated sewage: the highest reduction of BOD5 and NH4-N. It included the values of quality parameters and indicators for the filtrates obtained at the lowest hydraulic load from columns filled with 60 cm of rubber tires or sand. The second group comprised the results for fillings containing foam, PET and rubber tires (the other hydraulic loads). It featured the highest reduction of total suspended solids and PO43−. Removal of easily biodegradable organic compounds was at a similar level in both cluster groups. The filter filled with polyester waste (wadding), which was as effective as 30 cm layer of sand, and the filters filled with 60 cm of sand working at the highest hydraulic load. Third group showed the lowest values of parameters and indicators for analysed filtrates.

Application of multidimensional clustering for an assessment of pollutants removal from domestic wastewater using a filter with a plastic waste filling

The paper discusses the effectiveness of pollutants removal from pre-treated domestic wastewater using a vertical-flow filter with a plastic-waste filling. Raw and treated wastewater samples were analyzed to assess the effectiveness of the removal of organic compounds (COD and BOD5), suspended solids, and nitrogen as N-NH4+ depending on the filter filling type and working volume. Multidimensional clustering, including the hierarchical and non-hierarchical method, proved to be an efficient source-data clustering tool. It was found that reduction of hardly biodegradable organic compounds, as indicated by COD, was the main criterion of affiliation to the respective clusters.The studies lasted for four months, and showed that operation of the filter filled with 0.5 V of the polyurethane foam sponge waste was characterized by the highest operating stability under varied organic loading rates (OLR) from 5.0 to 80.2 g COD·m−3·d-1). On average, COD, BOD5, suspended solids and N-NH4+ reductions for that filter type were 87.8%, 91.0%, 80.0%, and 74.1%, respectively. In the removal of hardly biodegradable organic compounds and suspended solids, comparable performance figures were recorded for poly(ethylene terephthalate) flakes at organic loading rate values of 3.05 g COD·m−3·d-1. In that case, average reductions of COD and suspended solids were 87.1%, and 84.0%, respectively.

Effect of earthworms and plants on the efficiency of verticalflow systems treating university wastewater.

One of the possible ways to improve the operation efficiency of constructed wetlands and to prevent their clogging is the application of earthworms. They have already been successfully applied for vermicomposting and for sludge dewatering and treatment. A few studies have already examined the effect of earthworms on the treatment of wastewater by vertical flow constructed wetlands (VFCWs), but none of them have provided a yearlong research result from an open-air system or compared the effect that different seasons in a temperate climate area can have on these invertebrates. The goal of this research was to estimate the effect that earthworms and plants have on VFCW's operation. Four mesocosms (a filter, a filter with earthworms, a VFCW and a VFCW with earthworms) were built and their influent and effluent water quality was monitored for a period of 1year. They were fed with wastewater coming from a building of the University of Bologna (Italy). The results have shown that the presence of earthworms in this specific system did not reduce the organic matter content of the substrate, but it has positively influenced plants' growth. However, since neither earthworms nor plants had a statistically significant effect on the effluent quality, it can be concluded that the integration of these invertebrates cannot improve wastewater treatment of vertical flow filters or constructed wetlands.

Effectiveness of indicator bacteria removal in vertical flow filters filled with natural materials

Effectiveness of indicator bacteria removal in vertical flow filters filled with natural materials

Bacterial community activity and dynamics in the biofilm of an experimental hybrid wetland system treating greywater.

The objectives of this study were to determine the biofilm microbial activity and bacterial community structure and successions in greywater treatment filters and to relate the treatment efficiency to the bacterial community parameters. This 10-month study was performed in a newly established experimental system for domestic greywater treatment that consisted of three parallel vertical flow filters (VFs) followed by a horizontal flow filter (HF). A rapid increase in the bacterial community abundance occurred during the first 85days of filter operations, followed by a short-term decrease and the stabilization of the 16S rRNA gene copy numbers at average levels of 1.2 × 109 and 3.2 × 108 copies/g dw in VFs and HF, respectively, until the end of the experiment. The dominant bacterial phyla and genera differed between the VFs and HF. The temporal variation in the bacterial community structure was primarily related to the species replacement, and it was significantly affected by the influent organic carbon and nitrogen compounds in the VFs and the ammonia and organic carbon in the HF filters. Despite the differences in the community structure and assembly mechanisms, the temporal dynamics of the bacterial community showed high congruence between the filter types. The treatment efficiency was related to the biofilm bacterial community diversity and abundance and the abundance of certain bacterial genera in the VF filters. The results suggest that the dominant pathway of nitrogen removal by greywater treatment VFs occurs via coupled heterotrophic nitrification and denitrification, while the contribution of aerobic denitrification is temporally variable in these filters.

Purification Efficiency and Microbial Characteristics of Four Biofilters Operated Under Different Conditions

To explore the effects of aeration, microbial acclimation period, and pool shape or flow pattern change on the purification efficiency of biofilters at the microbiological level, four biofilters with different working conditions, that is, MAVF, NAVF, NVF, and BHF, were studied. The first three are vertical-flow biofilters and the last one is a baffled-flow biofilter. The four filters filled with the same ceramsite were made of organic glass. The MAVF filter was connected with the BHF filter in series and was operated for one year prior to the trial. The NAVF and NVF filters are newly activated filters. The four filters that were used to treat domestic sewage were synchronously operated in batch mode in this study. The MAVF and NAVF filters were intermittently aerated in contrast to the other two. During the period of microbial acclimation of the newly activated filters, the purification efficiency of the four filters was continuously monitored and the microbial community structure characteristics were analyzed at the end of microbial acclimation. The results show that the purification efficiency of the three vertical-flow filters is significantly higher than that of the horizontal-flow one and aeration significantly enhances the purification efficiency. However, aeration has a weaker effect on the efficiency than the microbial maturity of the filter. An apparent accumulation of nitrates or nitrites in the four filters was not observed, indicating that the denitrification was rather thorough. The 16S rDNA high-throughput sequencing analysis shows that the diversity index of the four filters is BHF > MAVF > NAVF > NVF, indicating that the more mature the filter is, the higher is the diversity index. Most of the packing microorganisms are facultative heterotrophic bacteria and the most abundant are heterotrophic denitrifying bacteria. Heterotrophic nitrification occurs in the NVF and BHF filters and aeration promotes the enrichment of aerobic ammonium-oxidizing bacteria. Aerobic phosphorus-accumulating organisms were not detected in the four filters. Therefore, phosphorus was mainly removed via denitrifying phosphorus accumulation. Under the test conditions, the removal rate of total nitrogen was not high, mainly because nitrifying bacteria were not enriched in the filter or their abundance was insufficient. The latter resulted in the limited ammonium-oxidizing ability of the filter, thus affecting the removal of total nitrogen. The above-mentioned results show that the adjustment of different working conditions will affect the redox status and associated enrichment of functional bacteria inside the biofilter, which will ultimately affect the purification efficiency.

Resilience and reliability of compact vertical-flow treatment wetlands designed for tropical climates

Most of the tropical areas have sanitation problems to contend with. The French system of vertical-flow treatment wetlands (FS-VFTW) fed with raw wastewater could be a good water and sludge management solution. The purpose-adapted tropical design can reduce area requirement to below 1 m2/population equivalents (p.e.). The Taupinière FS-VFTW on Martinique Island was built according to this design, with one stage but with a saturated layer at the bottom of the filter and a simplified trickling filter (TF) added for further treatment to meet the high performances targeted. Unsaturated/saturated vertical-flow filters (US/S FS-VFTW) have shown improved performances on total nitrogen, carbon and suspended solids removal in temperate climates, but the performances in tropical conditions remain unknown.Here, we report on real-world-operation in the French Overseas Territories (FOT), the reliability and performances of this VFCW tropical-design. The system experienced loading conditions ranging from 30% to 165% of nominal carbonaceous biological oxygen demand (BOD5), as well as tropical rainstorms that brought over 7 times the nominal hydraulic load. Over a period of 3 years, 29 campaigns collected 24-h flow-proportional samples at each treatment stage (raw wastewater, FS-VFTW outlet, TF outlet). When applied loads were close to nominal values, the US/S FS-VFTW itself guarantees 85/90/60/50% removal and 125/25/40/50 mg/L at the outlet for chemical oxygen demand (COD)/total suspended solids (TSS)/total Kjeldahl nitrogen (TKN)/total nitrogen (TN), respectively. By comparison with US/S systems in mainland France, it appears that the warmer tropical-climate temperatures facilitate both nitrification and denitrification kinetics.Performances in overload conditions confirm that the US/S FS-VFTW remains robust and reliable although COD and TKN removal are impacted, especially after strong tropical rain events. By adding a simple compact trickling filter to a US/S FS-VFTW, the treatment system delivers high-level performances (>95% removal for BOD5, COD, TSS and TKN) at less than 1 m2/p.e.

Urban stormwater treatment by a constructed wetland: Seasonality impacts on hydraulic efficiency, physico-chemical behavior and heavy metal occurrence

Urban stormwater affects the general quality of water bodies because of their hydraulic and pollution impacts. Stormwater discharges modify stream water flow and are reported as major source of heavy metals (HMs) in urban streams. Stormwater Constructed Wetlands (SCWs) have been built worldwide to manage stormwater before it is released into hydrosystems. In SCWs, stormwater is stored, evaporated and sometimes infiltrated. Subsequently, the HMs in stormwater can be settled, filtered and bioassimilated by microorganisms. Hence, the efficiency of SCWs in managing stormwater depends on climatic conditions, which change with season. The aim of this study was to investigate the impacts of seasonality on the performance of a 6-year-old constructed wetland made with a pond followed by a vertical flow filter. Hydraulic performance of, physico-chemical behaviour of, and HM mitigation via the SCW were evaluated using over 3 years of monitoring (2015–2017) data. Only 35% of the rain events that occurred in the studied catchment caused a discharge into the pond and 17% into the filter. The SCW was mostly supplied with stormwater in spring and summer and provided peak flow attenuation from 97 to 100% in all seasons. Variations in physico-chemical parameters (temperature, dissolved oxygen, pH, and redox potential) were caused by seasonal and dry/wet weather changes. They were greater in the pond than in the filter, which buffers these variations. The high physico-chemical variations in the pond probably had a deleterious effect on HM storage in the pond sediments. Finally, hydrologic and physico-chemical conditions (antecedent dry period length, pH, redox potential) affected the HM concentrations along the SCW. However, HM removal efficiencies were >97% in all seasons.

A single-output model for the dynamic design of constructed wetlands treating combined sewer overflow

Constructed wetlands treating combined sewer overflow (CSO CWs) are vertical flow filters in France, with outflow limitation and detention basin. Treating storm-generated flows reduces pollutants and flow peaks entering natural waters. Storm-generated flows are stochastic and therefore optimized CSO CW design requires a dynamic approach, i.e., a modelling software targeting engineers. Therefore a new tool, called Orage, was developed. Orage consists of a core model, an iterative shell and a user interface. It optimizes dimensions and materials of CSO CWs site-specifically, based on inflow series and a low number of input parameters. The core model simulates hydraulics and TSS, COD and NH4-N removal. Manual fitting of the core showed good results with a single load. The same parameters gave satisfying accuracy when simulating load series with closed material balance. Sensitivity analysis confirmed model robustness and justified coupling with an automatic shell algorithm for automatic optimization, based on a single output.