Upflow Filter Research Articles

Combination of granular activated carbon adsorption and deep-bed filtration as a single advanced wastewater treatment step for organic micropollutant and phosphorus removal

Adsorption onto granular activated carbon (GAC) is an established technology in water and advanced wastewater treatment for the removal of organic substances from the liquid phase. Besides adsorption, the removal of particulate matter by filtration and biodegradation of organic substances in GAC contactors has frequently been reported. The application of GAC as both adsorbent for organic micropollutant (OMP) removal and filter medium for solids retention in tertiary wastewater filtration represents an energy- and space saving option, but has rarely been considered because high dissolved organic carbon (DOC) and suspended solids concentrations in the influent of the GAC adsorber put a significant burden on this integrated treatment step and might result in frequent backwashing and unsatisfactory filtration efficiency. This pilot-scale study investigates the combination of GAC adsorption and deep-bed filtration with coagulation as a single advanced treatment step for simultaneous removal of OMPs and phosphorus from secondary effluent. GAC was assessed as upper filter layer in dual-media downflow filtration and as mono-media upflow filter with regard to filtration performance and OMP removal. Both filtration concepts effectively removed suspended solids and phosphorus, achieving effluent concentrations of 0.1 mg/L TP and 1 mg/L TSS, respectively. Analysis of grain size distribution and head loss within the filter bed showed that considerable head loss occurred in the topmost filter layer in downflow filtration, indicating that most particles do not penetrate deeply into the filter bed. Upflow filtration exhibited substantially lower head loss and effective utilization of the whole filter bed. Well-adsorbing OMPs (e.g. benzotriazole, carbamazepine) were removed by >80% up to throughputs of 8000–10,000 bed volumes (BV), whereas weakly to medium adsorbing OMPs (e.g. primidone, sulfamethoxazole) showed removals <80% at <5,000 BV. In addition, breakthrough behavior was also determined for gabapentin, an anticonvulsant drug recently detected in drinking water resources for which suitable removal technologies are still largely unknown. Gabapentin showed poor adsorptive removal, resulting in rapid concentration increases. Whereas previous studies classified gabapentin as not readily biodegradable, sustained removal was observed after prolonged operation and points at biological elimination of gabapentin within the GAC filter. The application of GAC as filter medium was compared to direct addition of powdered activated carbon (PAC) to deep-bed filtration as a direct process alternative. Both options yielded comparable OMP removals for most compounds at similar carbon usage rates, but GAC achieved considerably higher removals for biodegradable OMPs. Based on the results, the application of GAC in combination with coagulation/filtration represents a promising alternative to powdered activated carbon and ozone for advanced wastewater treatment.

Avaliação técnico-econômica da tecnologia de tratamento de água de dupla filtração

RESUMO O artigo avaliou a tecnologia de dupla filtração visando definir os critérios de seleção. A literatura é unanime em afirmar que na dupla filtração é necessário realizar o anteprojeto dos dois tipos de instalações (com filtro ascendente em pedregulho - FAP e com filtro ascendente em areia grossa - FAAG) e, em seguida, fazer um estudo técnico-econômico para determinar a melhor alternativa a ser implantada. No Brasil inexiste literatura que facilite a seleção da tecnologia em questão; assim, o artigo apresenta diretrizes que orientam a escolha da dupla filtração, facilitando o trabalho dos engenheiros projetistas. No estudo, os custos de 50 sistemas de dupla filtração foram analisados. Os resultados indicaram que o gerenciamento dos resíduos, a escavação e o consumo de energia elétrica na dupla filtração com FAAG podem incrementar o valor presente em até 33% quando comparado à com FAP; o resultado é válido para sistemas com vazões entre 10 e 100 L.s-1. Os gastos advertem que o engenheiro projetista deve justificar a seleção da dupla filtração com FAAG; portanto, os custos devem ser avaliados e confrontados com o risco microbiológico presente no manancial.

Fate and transport with material response characterization of green sorption media for copper removal via adsorption process.

Green adsorption media with the inclusion of renewable and recycled materials can be applied as a stormwater best management practice for copper removal. A green adsorption media mixture composed of recycled tire chunk, expanded clay aggregate, and coconut coir was physicochemically evaluated for its potential use in an upflow media filter. A suite of tests were conducted on the media mixture and the individual media components including studies of particle size distribution, isotherms, column adsorption and reaction kinetics. Isotherm test results revealed that the coconut coir had the highest affinity for copper (q(max) = 71.1 mg g(-1)), and that adsorption was maximized at a pH of 7.0. The coconut coir also performed the best under dynamic conditions, having an equilibrium uptake of 1.63 mg g(-1). FE-SEM imaging found a strong correlation between the porosity of the micro pore structure and the adsorptive capacity. The use of the green adsorption media mixture in isolation or the coconut coir with an expanded clay filtration chamber could be an effective and reliable stormwater best management practice for copper removal.

Evaluation of chlorophyll and anti-oxidative components harvested from the anaerobic digestion of fruit and vegetable waste

Abstract Two-phase up-flow sludge blanket filter (TUBF) digestion process of fruit and vegetable waste homogenate generated anaerobic sludge with concentrated pigments and reducing compounds. In the 5–50 L scale-up daily batch and semi-batch operations, the organic loading rate attained was over 6 kg COD/m 3 .day. A comparative study indicated that Minox polyethylene ring packing was critical for optimization of anaerobic digestion. The biogas production in terms of the volatile fatty acid pattern with a C 2 –C 6 level of 600 mg/L through liquefaction and acidification (LA) maintained the alkalinity over 3500 mg/L and stabilized the pH of the LA phase at 5.2–6.8 according to the loading status. In the semi-batch operation of 50 L, pigments gradually condensed in the sludge layer were concentrated by a factor of at least ten fold, and a high level of reducing activity was retained by the chlorophyll and anti-oxidative components.

Investigation into the Optimum Hydraulic Loading Rate for Selected Filter Media Packed in a Continuous Upflow Filter

Abstract— Continuous upflow filters can combine the nutrient (nitrogen and phosphate) and suspended solid removal in one unit process. The contaminant removal could be achieved chemically or biologically; in both processes the filter removal efficiency depends on the interaction between the packed filter media and the influent. In this paper a residence time distribution (RTD) study was carried out to understand and compare the transfer behaviour of contaminants through a selected filter media packed in a laboratory-scale continuous up flow filter; the selected filter media are limestone and white dolomite. The experimental work was conducted by injecting a tracer (red drain dye tracer –RDD) into the filtration system and then measuring the tracer concentration at the outflow as a function of time; the tracer injection was applied at hydraulic loading rates (HLRs) (3.8 to 15.2 m h -1 ). The results were analysed according to the cumulative distribution function F(t) to estimate the residence time of the tracer molecules inside the filter media. The mean residence time (MRT) and variance σ

Experimental evaluation of ripening behavior: Down-Flow vs. Up-Flow rapid sand filters

Filter ripening is progressive development of media charge and build-up of collector efficiency, during starting phase of granular filtration. In the present work, a comparative study of ripening behavior was carried out by conducting simultaneous laboratory filtration experiments on Down-Flow (DF) and Up-Flow (UF) sand filters. The artificial influent was used for filtration studies. It was prepared to replicate pretreated low turbidity surface water. The Filter Ripening Sequence (FRS) curve for the UF filter was observed to be significantly distinct. It was corroborated that the ripening depends on filtration rate (v) for the both filters. Enhancement in the ripening performance of the both filters was witnessed for the influents with less negative zeta potential of influent particles (ζp). Further, the technique of Extended Terminal Sub-fluidized Wash (ETSW) with cationic polymer in wash water was also tested to improve ripening process. It was found effective in reducing initial degradation of effluent for the both filters. However, the ETSW with polymer modified wash water resulted in considerable increase in head loss during ripening for the DF filter. Particularly, the incremental increase in head loss subsequent to polymer modified ETSW was less for the UF filter.

Anaerobic treatment of rice winery wastewater in an upflow filter packed with steel slag under different hydraulic loading conditions

Rice-washing drainage (RWD), a strong organic wastewater, was anaerobically treated using an upflow filter filled with blast-furnace slag. The continuous performance of the reactor was examined at varying hydraulic retention times (HRTs). The reactor achieved 91.7% chemical oxygen demand removal (CODr) for a 10-day HRT (0.6gCOD/Ld organic loading rate) and maintained fairly stable performance until the HRT was shortened to 2.2days (CODr>84%). Further decreases in HRT caused process deterioration (CODr<50% and pH<5.5 for a 0.7-day HRT). The methane production rate increased with decreasing HRT to reach the peak level for a 1.3-day HRT, whereas the yield was significantly greater for 3.4-day or longer HRTs. The substrate removal and methane production kinetics were successfully evaluated, and the generated kinetic models produced good performance predictions. The methanogenic activity of the reactor likely relies on the filter biofilm, with Methanosaeta being the main driver.

&lt;b&gt;Proposal for initial collection efficiency models for direct granular upflow filtration

Mathematical models of the filtration process are based on the mass balance in the filter bed. Models of the filtration phenomenon describe the mass balance in bed filtration in terms of particle removal mechanisms, and allow for the determination of global particle removal efficiencies. This phenomenon is defined in terms of the geometry and the characteristic elements of granule collectors, particles and fluid, and the composition of the balance of forces that act in the particle collector system. This type of resolution is well known as the trajectory analysis theory. Particle trajectory analysis by mathematical correlation of the dimensionless numbers that represent fluid and particle characteristics is considered the main approach for mathematically modeling the initial collection efficiency of particle removal in water filtration. The existing initial collection efficiency models are designed for downflow filtration. This study analyzes initial collection efficiency models, and proposes an adaptation of these models to direct upflow filtration in a granular bed of coarse sand and gravel, taking into account the contribution of the gravitational factor of the settling removal efficiency in the proposal of initial collection efficiency models.

Performance of upflow gravel filtration in multi-stage filtration plants.

This paper presents the results of a study of four full-scale upflow gravel filters that are part of full-scale multi-stage filtration. The study explored the design criteria, the operation and maintenance (O&M) practices, and the performance of the systems. Findings showed that most design criteria and O&M procedures are following the recommendations as presented in the literature but several diversions were also identified. Performance data showed that removal efficiencies were on the low side when compared to the literature, possibly because of the good influent quality water that was treated. Cleaning efficiency was analyzed and the overall conclusion is that an adjustment of the design criteria and O&M procedures is needed to enhance system performance. This includes drainage system design, surface cleaning by weir, and filter bed cleaning to allow a reduction in cleaning cycles and an improvement in operation control.

Investigation of geometric properties of media particles and operating conditions on floating media filtration

Filtration is an effective process in removing particles that are present in water. Floating medium filter has been used in direct filtration because of its flexibility, cost savings gained by less land requirements, and less water and energy required for backwashing. The aim of this work was to investigate the effect of geometric properties of a floating medium in upflow filtration mode. A pilot plant was designed and constructed to evaluate the filtration process. Effect of physical parameters on filtration performance was also investigated. The experiments were carried out using a commonly available polypropylene floating medium. Four median grain sizes (2.28, 3.03, 3.30, and 4.07 mm) of polypropylene plastic pellets were used. Two media shapes (cubic and disc) were evaluated. Bentonite (250 mg/L ≈ 60 NTU) was used to make up the raw feed water. Three parameters that could influence the filtration performance were identified, namely: filtration velocity, media depth, and coagulant dose. The results showed that the best conditions to remove turbidity were found to be: low filtration rate (36.8 L/m2 min), longer media depth (600 mm) and optimum coagulant dose (23 mg/L). The results also indicated that the smaller plastic medium (2.28 mm) was more efficient in terms of turbidity removal than the larger medium. However, headloss development associated with smaller media was higher (109 mm of water) than that associated with larger medium (42 mm of water).

Anaerobic transformation of Cationic Red X-GRL with low levels of carbon source

In this study, an anaerobic upflow biological filter (UBF) was used for the treatment of Cationic Red X-GRL (X-GRL)-containing wastewater with low concentrations of carbon sucrose. The performance and mechanisms involved in the color removal and aromatic amine transformation under anaerobic condition were investigated. The results showed that all color and more than 90% of aromatic compounds were removed by UBF with 200 mg/L of X-GRL and 50 mg/L of sucrose in the influent, which indicates the UBF is effective for degrading X-GRL with a low concentration of carbon source. The sucrose acted as an initial electron donor for X-GRL reduction, and the EPS and aromatic compounds also donated electrons for the cleavage of azo bond, leading to decolorization of X-GRL. The addition of X-GRL improved the anaerobic degradation of aromatic compounds. The bacterial and archaeal communities in the anaerobic sludge were determined by clone library method as well.

Hydraulic analysis of an upflow sand filter: Tracer experiments, mathematical model and CFD computation

Sand filters are gradually being adapted for use in the water treatment. The hydraulic performance of the filter bed directly affects the pollutant removal performance. Tracer experiments and residence time distribution (RTD) theory were used to characterize the flow in a special upflow sand bed filter. The detailed flow pattern of the reactor was obtained from computational fluid dynamics (CFD) simulation. An orthogonal analysis was adopted to optimize the filter's structures, including the piping network, free-water surface and bearing-layer. The RTD study and CFD simulation show that the free-water surface and the bearing-layer have the functions of collecting and distributing water, respectively. The free-water surface and the bearing-layer have little effect on the flow pattern when the network is distributed throughout the water-carrying section. However, when the piping network is distributed in the partial carrying section, the free-water surface and the bearing-layer can improve the hydrodynamics as well as eliminate preferential/shortcut flow and stagnant volume. The orthogonal analysis shows that the order of factors with regard to the effect on volume efficiency is as follows: bearing-layer > free-water surface > piping network. There are marked interactions between the factors. The reactor with partially piping network, free-water surface and bearing-layer had the highest volume efficiency. The flow pattern is close to plug flow and the normalized mean retention time is 1.093. Increasing the packing medium diameter in the fully piping network reactor greatly decreases the unavailable volume, while the diameter in partially piping network reactors does not significantly change the water flow pattern in reactors.

Treatment of high turbidity water through plain and coagulated up-flow roughing filter

Khokhar Zar Dam in Chakwal, Pakistan, serves as a main source of water supply to the area. This water is not only turbid but also biologically polluted. A hybrid slow sand filtration (SSF) plant, involving coagulation and sedimentation prior to SSF, is employed for the treatment. The treatment train is sensitive to wide variations in raw water turbidity and often results into short filter runs. Major objective of this research was to study the existing treatment process and conduct a pilot-scale investigation for the most appropriate treatment scheme, using an up-flow multistage roughing filter. A three-stage up-flow roughing filter (UFRF) was tested in plain and coagulated mode for a range of flow rates. Results showed that raw water turbidity reduced to 30 NTU in dry period and rose to over 2000 NTU after rainfall, whereas raw water pH and conductivity remained consistent. Jar tests showed that higher FeCl3 dose (65 mg/L) would be required when compared with alum (47 mg/L). Plain multistage UFRF demonstrated 30–50% turbidity removal, whereas coagulated UFRF showed 99% turbidity removal at 35% of the dose applied by the treatment plant. Effectiveness of coagulated filtration continued even after the dose supply was ceased.

OPERATIONAL PERFORMANCE OF VERTICAL UPFLOW ROUGHING FILTER FOR PRE-TREATMENT OF LEACHATE USING LIMESTONE FILTER MEDIA

This study was conducted to investigate the removal of COD, BOD, turbidity and colour from leachate using vertical upflow filtration technique. Limestone media with a density of 2554kg/m3 was crushed and graded in sizes of 4-8 mm, 8-12 mm and 12-18 mm. Trial runs were done before the main experiment at an interval of 24 h analysis. Leachate was between pH 7.94 to 8.12 before experiments but increased to pH 8.42 after the filtration process. Maximum headloss at steady flow rate 20mL/min was 0.5 cm. The optimum treatment was achieved with 4 – 8 mm, 8 – 12 mm &amp; 12 – 18 mm media size in combination and removal efficiency was 22 to 81 %, 22 to 75 %, 32 to 86 %, and 36 to 62 % for BOD, COD, turbidity and colour respectively. Vertical upflow roughing filter can be used for pre-treatment of leachate before further treatment.

OPERATIONAL PERFORMANCE OF VERTICAL UPFLOW ROUGHING FILTER FOR PRE-TREATMENT OF LEACHATE USING LIMESTONE FILTER MEDIA

This study was conducted to investigate the removal of COD, BOD, turbidity and colour from leachate using vertical upflow filtration technique. Limestone media with a density of 2554kg/m3 was crushed and graded in sizes of 4-8 mm, 8-12 mm and 12-18 mm. Trial runs were done before the main experiment at an interval of 24 h analysis. Leachate was between pH 7.94 to 8.12 before experiments but increased to pH 8.42 after the filtration process. Maximum headloss at steady flow rate 20mL/min was 0.5 cm. The optimum treatment was achieved with 4 – 8 mm, 8 – 12 mm &amp; 12 – 18 mm media size in combination and removal efficiency was 22 to 81 %, 22 to 75 %, 32 to 86 %, and 36 to 62 % for BOD, COD, turbidity and colour respectively. Vertical upflow roughing filter can be used for pre-treatment of leachate before further treatment.

Self-cleaning filtration: A novel concept for rainwater harvesting systems

The treatment of rainwater is typically performed by the diversion of the first flush and the use of strainers to retain gross particles (e.g. leaves). To date, there is a lack of rainwater treatment systems with both high efficiency to remove small suspended particles, and simple operation without energy consumption and associated greenhouse gas emissions. The objective of this work was to develop and test a novel concept for the filtration of particles in raw rainwater with no energy usage, self-cleaning mechanism, and simple installation and operation in buildings. For this purpose, an innovative concept was developed based on an up-flow filtration with down-flow backwashing operation. The concept was tested by building a prototype, in which the treatment efficiency for particle removal as well as the backwash efficiency were assessed for three different filter media. Results showed that the system designed under the proposed concept operated effectively with the correct selection of the filter medium. Therefore, the proposed rainwater treatment concept offers an opportunity to enhance water security by treating and using rainwater in buildings in an efficient, simple, and energy-free way.

Low-cost multi-stage filtration enhanced by coagulation-flocculation in upflow gravel filtration

Abstract. This paper assesses the operational and design aspects of coagulation and flocculation in upflow gravel filters (CF-UGF) in a multi-stage filtration (MSF) plant. This study shows that CF-UGF units improve the performance of MSF considerably, when the system operates with turbidity above 30 NTU. It strongly reduces the load of particulate material before the water enters in the slow sand filters (SSF) and therewith avoids short filter runs and prevents early interruption in SSF operations. The removal efficiency of turbidity in the CF-UGF with coagulant was between 85 and 96%, whereas the average efficiency without coagulant dosing was 46% (range: 21–76%). Operating with coagulant also improves the removal efficiency for total coliforms, E-coli and HPC. No reduction was observed in the microbial activity of the SSF, no obstruction of the SSF bed was demonstrated and SSF runs were maintained between 50 and 70 days for a maximum head loss of 0.70 m. The most important advantage is the flexibility of the system to operate with and without coagulant according to the influent turbidity. It was only necessary for 20% of the time to operate with the coagulant. The CF-UGF unit represented 7% of total construction costs and the O&amp;amp;M cost for the use of coagulant represented only 0.3%.

Water treatment by multistage filtration system with natural coagulant from Moringa oleifera seeds

This study presents an evaluation of a pilot multistage filtration system (MSF) with different dosages, 131 mg L-1 and 106 mg L-1, of the natural coagulant extracted from Moringa oleifera seeds in pre-filtration and slow filtration stages, respectively. The system was comprised by a dynamic pre-filter unit, two upflow filters in parallel and four slow filters in parallel, and in one of the four filters had the filter media altered. The performance of the system was evaluated by monitoring some water quality parameters such as: turbidity, apparent color and slow filter load loss. The stages that have received the coagulant solution had better treatment efficiency compared with the steps without it. However, the direct application of the coagulant solution in the slow filter caused rapid clogging of the non-woven blanket and shorter career length.

Hydrodynamic analysis of particle collection efficiency: comparing downflow and upflow filtration

Models of the filtration phenomenon describe the mass balance in bed filtration in terms of particle removal mechanisms, and allow for the determination of global particle removal efficiencies. These models are defined in terms of the geometry and characteristic elements of granule collectors, particles and fluid, and also the composition of the balance of forces that act in the particle collector system. This work analyzes particles collection efficiency comparing downflow and upflow direct filtration, taking into account the contribution of the gravitational factor of the settling removal efficiency in future proposal of initial collection efficiency models for upflow filtration. A qualitative analysis is also made of the proposal for the collection efficiency models for particle removal in direct downflow and upflow filtration using a Computational Fluid Dynamics (CFD) tool. This analysis showed a strong influence of gravitational factor in initial collection efficiency (t = 0) of particles, as well as the reasons of their values to be smaller for upflow filtration in comparison with the downflow filtration.

Tratamento de água de reservatórios por dupla filtração, oxidação e adsorção em carvão ativado granular

Este trabalho teve como objetivo avaliar o tratamento de água bruta proveniente de um reservatório de água, utilizando instalação piloto de dupla filtração (DF), composta por filtro ascendente de pedregulho (FAP) e filtro rápido descendente de areia (FRD), seguida de uma unidade de pós-tratamento com carvão ativado granular (CAG). Adicionalmente, foi verificado o efeito da pré e interoxidação (entre o FAP e o FRD) na eficiência global do tratamento e na formação de subprodutos orgânicos halogenados (SOH). Em função dos resultados obtidos, foi observado que a pré-oxidação melhorou a qualidade do efluente do FAP e a interoxidação favoreceu que resultassem valores menores de turbidez e cor no efluente do FRD. O processo de tratamento por adsorção em carvão ativado granular, utilizado como pós-tratamento, mostrou-se eficiente para assegurar a qualidade dos efluentes finais nos ensaios realizados, especialmente, em relação à remoção de matéria orgânica, cianobactérias e cor. As concentrações máximas de SOH encontrados nos efluentes do FRD e do FCAG não ultrapassaram os valores limites da Portaria nº 2.914/2011 do Ministério da Saúde.