Pilot-scale Trickling Filter Research Articles

Simulated Modelling, Design, and Performance Evaluation of a Pilot-Scale Trickling Filter System for Removal of Carbonaceous Pollutants from Domestic Wastewater

The aim of the present study is to assess the wastewater treatment efficiency of a low-cost pilot-scale trickling filter (TF) system under a prevailing temperature range of 12 °C–38 °C. Operational data (both influent and effluent) for 330 days were collected from the pilot-scale TF for various physicochemical and biological parameters. Average percentage reductions were observed in the ranges of 52–72, 51–73, 61–81, and 74–89% for BOD5, COD, TDS, and TSS, respectively, for the whole year except the winter season, where a 74–88% reduction was observed only for TSS, whilst BOD5, COD, and TDS demonstrated reductions in the ranges of 13–50, 13–49, and 23–61%, respectively. Furthermore, reductions of about 43–55% and 57–86% in fecal coliform count were observed after the 1st and 6th day of treatment, respectively, throughout study period. Moreover, the pilot-scale TF model was based on zero-order kinetics calibrated at 20 °C using experimental BOD5 data obtained in the month of October to calculate the k20 value, which was further validated to determine the kt value for each BOD5 experimental setup. The model resulted in more accurate measurements of the pilot-scale TF and could help to improve its ability to handle different types of wastewater in the future.

Investigation of municipal wastewater treatment by agricultural waste materials in locally designed trickling filter for peri-urban agriculture

Abstract A pilot scale trickling filter system was designed, developed, and operated using a constant recirculation method for treatment of municipal wastewater. Maize cob (TF1) and date palm fibre (TF2) were used as biofilm support media in a trickling filter system. Both the TF1 and TF2 were compared based on the removal efficiency of pollution indicators such as biological oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS), total suspended solids (TSS), electrical conductivity (EC), total nitrogen (TN), total phosphorus (TP) and sulphates. The hydraulic flow rate and loading were set as 0.432 m3/h and 0.0064 m3/m2.minute, respectively at temperature range of 15–42 °C for 15 operational weeks. Both the TF1 and TF2 showed acceptable removal efficiency (61% to 76.3%) for pathogen indicators such as total count, fecal coliforms and Escherichia coli. However, 8–15% higher removal efficiency was observed for TF1 for all the pollution indicators compared to TF2. The results suggest that both the biofilm support media in trickling filter have potential to treat municipal wastewater in peri-urban small communities to produce environmentally friendly effluent.

Combined chemically enhanced primary sedimentation and biofiltration process for low cost municipal wastewater treatment

The main objective of wastewater treatment is to remove carbon and other nutrients from municipal and industrial effluents in order to protect the environment and human health. Typical wastewater treatment is usually achieved by a combination of physical, chemical and biological methods. In this work, municipal wastewater was depurated using chemically enhanced primary treatment (CEPT) in combination with a pilot-scale trickling filter. Lab scale experiments (Jar-tests) were carried out in order to determine the optimum dosage of chemicals. Selection criteria were the organic load removal efficiency and the low operational cost. Coagulation-flocculation process was conducted through polyaluminium chloride (PAC) and the cationic polyelectrolyte (Zetag 8180) addition. By combining CEPT and trickling filter, tCOD (total Chemical Oxygen Demand), sCOD (soluble Chemical Oxygen Demand), BOD5 (5-day Biochemical Oxygen Demand), NH4+-N, TSS (Total Suspended Solids), VSS (Volatile Suspended Solids) and PO43−-P removal efficiencies were estimated to be 89, 82, 93, 60, 96, 96 and 78%, respectively. It is concluded that biological filtration contributed significantly in nutrients removal processes. Moreover, the obtained effluent was low in carbon and rich in nitrogen, which can be applied for restricted irrigation after disinfection, complying with the discharge limits set in the Greek Joint Ministerial Decree 145116/2011.

Application of pilot scale trickling filter couple with pre-ozonation for ammonia, iron and dissolved organic carbon removals from Saigon river water

A pilot scale trickling filter and pre-ozonation contactor with capacity of about 20 m3/day was run at Hoa Phu Pump Station which takes raw water from Saigon River for drinking water supply for Ho Chi Minh City. The raw water contains 0.52 ± 0.19 mg NH4+-N/l, 0.14 ± 0,06 mg/l total iron and 3.14 ± 0.45 mg/l DOC. The study aimed to using the pilot scale experiment to assess ammonia, iron and dissolved organic carbon (DOC) removals from Saigon Water River for the sake of reducing chlorine demand and thus mitigating risk from Disinfection By Products (DBPs) formation. The size of the trickling filter was 0.5 m long x 0.5 wide x 2m high. The bio-media was seven PE wool sheets with thickness of 30 mm that is widely used as filter cloth in aquariums. It run at hydraulic loading of 3 m3/m2.h of raw water, and 8 m3/m2.h, where 50% of total flow was the returned effluent of pre-ozonation. The pilot scale pre-ozonation contactor which has the size of 0.6 m long x 0.6 m wide x 2.0 m high was operated at contact time of 15 minutes and ozone concentration of 0.5 mg/l. The ammonia, iron and DOC removals at 8 m3/m2.h were 58%, 25% and 22%, respectively. Whereas, it obtained ammonia, iron and DOC removals of 52%, 19% and 9% DOC respectively. Thus, even though the experiment with returned pre-ozonation effluent run at high hydraulic loading rate, the better performance was obtained as comparison to the experiment without return.

Efficiency of a pilot scale trickling filter to treat industrial brewery wastewater: Influence of hydraulic loading

BACKGROUND Despite sound technological improvements, huge water consumption and the associated wastewater discharge remain one of the major environmental challenges in the brewing industry. The aim of this study is therefore to investigate the performance of a mineral filled pilot scale trickling filter to treat brewery wastewater. A trickling filter is superior over the other conventional wastewater treatment processes in terms of cost and environmental friendliness therefore it is recommendable particularly for low income countries. RESULTS Pilot scale plant experiments were made to evaluate the trickling filter aerobic and anaerobic biofilm systems for removal of organics and nutrients from brewery wastewater at different hydraulic loading rates. The trickling filter had an average efficiency of (86.53), (95.25), (69.93) and (41.03)% for biochemical oxygen demand (COD), biological oxygen demand (BOD5), total nitrogen (TN) and total phosphorus (TP), respectively, as the flow rates changed from 900 to 1100 L day-1at an influent COD concentration of 600 mg L-1. A linear regression model revealed that there is very high correlations between mass loading rate and mass removal rate. The results of this study suggest that in addition to significant values for nutrient removal efficiencies, effluent value in the range 50 − 120 mg L-1 COD can be achieved using the trickling filter at the design hydraulic load and organic load of 8.36 m-3 m-2 day-1 and 0.75 k g m-3 d-1, respectively. CONCLUSION Organic substances and nutrients in brewery wastewater can be handled in a cost-effective and environmentally friendly manner using the gravel-filled trickling filter. © 2014 Society of Chemical Industry

A pilot scale trickling filter with pebble gravel as media and its performance to remove chemical oxygen demand from synthetic brewery wastewater

Evaluating the performance of a biotrickling filter for the treatment of wastewaters produced by a company manufacturing beer was the aim of this study. A pilot scale trickling filter filled with gravel was used as the experimental biofilter. Pilot scale plant experiments were made to evaluate the performance of the trickling filter aerobic and anaerobic biofilm systems for removal of chemical oxygen demand (COD) and nutrients from synthetic brewery wastewater. Performance evaluation data of the trickling filter were generated under different experimental conditions. The trickling filter had an average efficiency of (86.81±6.95)% as the hydraulic loading rate increased from 4.0 to 6.4 m(3)/(m(2)∙d). Various COD concentrations were used to adjust organic loading rates from 1.5 to 4.5 kg COD/(m(3)∙d). An average COD removal efficiency of (85.10±6.40)% was achieved in all wastewater concentrations at a hydraulic loading of 6.4 m(3)/(m(2)∙d). The results lead to a design organic load of 1.5 kg COD/(m(3)∙d) to reach an effluent COD in the range of 50-120 mg/L. As can be concluded from the results of this study, organic substances in brewery wastewater can be handled in a cost-effective and environmentally friendly manner using the gravel-filled trickling filter.

Biological Cr(VI) reduction in a trickling filter under continuous operation with recirculation

BACKGROUND: Hexavalent chromium (Cr(VI)) is toxic to humans, animals and plants. Conventional treatment technologies reduce Cr(VI) to the less toxic and mobile Cr(III), but these methods are usually expensive and generate secondary waste. Microbial Cr(VI) reduction has recently gained attention as a detoxification process, since it enables Cr(VI) reduction through relatively cheap and simple methods. The aim of this work was to investigate the mechanism and the performance of biological Cr(VI) reduction using mixed cultures originated from industrial sludge under continuous operation with recirculation in a pilot-scale trickling filter. RESULTS: Biological Cr(VI) reduction was studied using a pilot-scale trickling filter filled with plastic media under continuous operation with recirculation and the use of indigenous bacterial population. The effect of the organic carbon (electron donor) concentration was examined for constant Cr(VI) influent concentration at about 5.5 mg L−1 and volumetric flow rates ranging from 60 to 900 mL min−1. The highest reduction rate achieved was 1117 g Cr(VI) m−2 d−1 for a volumetric flow rate of 900 mL min−1. The system's reduction capacity was significantly affected by chromate loadings, resulting in frequent backwashing of the filter. The determination of the reduction mechanism was also studied using batch cultures of free suspended cells and culture supernatant. CONCLUSION: The high reduction rates combined with the low operating cost indicate that the above technology can be a viable solution for the treatment of industrial chromate effluents. Copyright © 2008 Society of Chemical Industry

Simultaneous biological removal of ammonia, iron and manganese from potable water using a trickling filter

A pilot-scale trickling filter with dual layer support material was constructed and tested for simultaneous biological removal of ammonia, iron and manganese from potable water. The performance of the trickling filter was tested at constant hydraulic loading of 226 m 3/m 2 d while feed concentrations of iron, ammonia and manganese were varied between 0.5 and 4.0, 0.5 and 3.0, and 0.5 and 1.3 mg/l, respectively. The system was inoculated with a mixed culture and a series of experiments was performed to investigate the interactions among ammonia, iron and manganese removal when simultaneously present in the trickling filter. The oxidation reduction potential increased along the filter depth from about 150 to 600 mV, depending on the feed concentrations, thus enabling one-stage simultaneous removal of the three pollutants. Ammonia and iron drastically affected manganese oxidation and manganese was found to be the rate-limiting pollutant. The results are presented using an operating diagram of the system, that determines the range of operating conditions resulting in optimal operation, keeping iron, ammonia and manganese concentration under the maximum permitted limits in potable water.

Biological manganese removal from potable water using trickling filters

Two pilot-scale trickling filters were constructed and tested for manganese removal from potable water, using different fractions of silicic gravel as support media (mono- and multilayer filter). Manganese oxidation in drinking water was found to be cause by both biological oxidation and heterogeneous catalytic paths. Mixed culture populations were used to inoculate the trickling filters and the feed manganese concentrations and volumetric flow rates (VFRs) were between 0.6–2.0 mg/l and 500–2000 ml/min, respectively. The monolayer filter was flooded for high VFRs, and it was very effective for all conditions tested (100% removal efficiency, up to 2850 mg Mn/day). The multilayer filter was less effective for high manganese concentrations but it could remove up to 3250 mg Mn/day. A new mathematical model was developed assuming heterogeneous autocatalytic and biological as the main oxidation manganese paths. First order kinetics was used to describe the heterogeneous catalytic oxidation, while Monod-type kinetics was used to describe the net biological manganese oxidation. The simplicity of the pilot-scale design, the lack of need for an external mechanical aeration source and the ability to predict operation of the system offers a very attractive solution for manganese removal from potable water.

Biological removal of hexavalent chromium in trickling filters operating with different filter media types

The purpose of the present study was to estimate Cr(VI) removal through biological mechanisms in biofilm reactors operated in SBR operating mode with recirculation using different filter media types. The choice of the support material is of great importance since chromate reduction is followed by the formation of sediments, which causes obstruction of the flow along the filter depth. In order to overcome this awkwardness, we tested the performance of two different support materials, i.e. plastic media and calcitic gravel, in pilot-scale trickling filters. The feed concentrations of Cr(VI) examined were about 5, 30 and 100 mg/l, while the concentration of the organic carbon was constant at 400 mg/l, in order to avoid carbon limitations in the bulk liquid. Plastic media showed better performance at the different Cr(VI) concentrations examined, compared to the gravel media. The removal rates for the plastic media achieved were 4.23±0.18, 3.62±0.1 and 3.3±0.08 g Cr(VI)/d, for feed concentration of Cr(VI) about 5, 30 and 100 mg/l respectively, while for the gravel media the corresponding removal rates were 4.11±0.09, 3.52±0.06 and 2.5±0.07 g Cr(VI)/d.

Ammonia, iron and manganese removal from potable water using trickling filters

Pilot scale trickling filters were constructed and tested in order to study biological removal of ammonia, iron and manganese from potable water. The effect of the size of the support material on nitrification performance was studied extensively. The mean size of the gravel and hence, the specific surface area was found to be critical for optimal nitrification operation. A steady-state model developed in previous work was used to predict filter's performance. The model was very accurate only for the gravel size for which maximum nitrification rates were observed. The effect of the operational conditions on the physico-chemical and combined physico-chemical and biological iron oxidation was also studied. It was found that the contribution of biological oxidation is significant, increasing filter's efficiency by about 6% and reducing the required filter depth by about 40%. Manganese biological removal was studied using gravel with small mean diameter, thus providing high specific surface area. Feed concentrations up to 4.0 mg/l were treated sufficiently. Finally, experiments were performed to investigate the simultaneous removal of ammonia, iron and manganese. Experimental results showed that the combined, as well as the simultaneous removal of the aforementioned pollutants, can be achieved by single-step filtration.

A kinetic study of biological Cr(VI) reduction in trickling filters with different filter media types

Two pilot-scale trickling filters were used in order to estimate Cr(VI) reduction through biological mechanisms in biofilm reactors operated in SBR mode with recirculation using different filter media types, i.e. plastic media and calcitic gravel. The feed concentrations of Cr(VI) examined were about 5, 10, 20, 30, 50 and 100 mg/l, while the concentration of the organic carbon was constant at 400 mg/l, in order to avoid carbon limitations in the bulk liquid. Maximum reduction rates of 4.8 and 4.7 g Cr(VI)/d were observed for feed Cr(VI) concentration of about 5 mg Cr(VI)/l, for the filters with the plastic support material and the gravel media, respectively. The reduction rates were significantly affected by the feed Cr(VI) concentration in both bioreactors. A dual-enzyme kinetic model was used in order to describe Cr(VI) reduction by aerobically grown mixed cultures. Model predictions were found to correspond very closely to experimental quantitative observations of Cr(VI) reduction at both pilot-scale trickling filters used.

Physico-chemical and biological iron removal from potable water

A pilot-scale trickling filter was constructed and tested for iron removal from potable water. Iron removal was found to be caused by both biological and physico-chemical iron oxidation. The extent of each oxidation type was assessed. The system was inoculated with mixed culture and its performance was tested under continuous operation at 14 °C. Feed iron concentrations and volumetric flow rates (VFR), ranged between 1–4 mg/l and 1000–3000 ml/min (225–680 m 3/m 2day), respectively. First order kinetics was used to describe the physico-chemical iron oxidation while Monod-type kinetics was used to describe the net biological iron oxidation. An increase of VFR from 1000 to 3000 ml/min reduced the filter's physico-chemical removal efficiency from 93 to 80%, while it remained constant for all the iron feed concentrations (1–4 mg/l) that were tested at each VFR. Bio-oxidation improved filter efficiency by about 5–6%. In all cases there was very good agreement between model predictions and experimental data. A series of experiments were also performed in order to investigate the simultaneous ammonia and iron oxidation. It was found that ammonia influence on iron removal becomes substantial only for high iron and ammonia concentrations. The simplicity of the pilot-scale design, the lack of the need for an external mechanical aeration source and the ease for the design and prediction of the system operation offers a very attractive solution for iron removal from potable water.

The Role of Bioflocculation on Suspended Solids and Particulate COD Removal in the Trickling Filter Process

Understanding that there is a significant presence of extracellular polymeric substances at the biofilm/wastewater interface and that the primary constituent of chemical oxygen demand (COD) in domestic wastewaters is organic particulates, this research describes the kinetics of particulate removal in a pilot-scale trickling filter (TF) and the role of bioflocculation in the removal process. Recent research has described the role of bioflocculation on particulate COD (PCOD) removal in suspended growth biological wastewater treatment systems. However, no research pertaining to PCOD removal by bioflocculation in attached growth systems was identified prior to this study. For this study, experiments were conducted using both bench- and pilot-scale biofilm reactors and provided evidence that the removal of organic and inorganic particulate matter in a TF bioreactor follows a first-order bioflocculation rate equation. The statistical analysis of data obtained from the pilot TF fits the dispersion model to suspended solids and PCOD remaining in the pilot TF.

Biological treatment of wastewaters from a dye manufacturing company using a trickling filter

The aim of this work was to assess the effectiveness of a biological trickling filter for the treatment of wastewaters produced by a company manufacturing organic dyes and varnishes. The combined wastewater effluent was fed to a pilot-scale trickling filter in two feeding modes, continuously and as a sequencing batch reactor (SBR). The biodegradability of the diluted wastewaters that were subjected to physicochemical treatment, using Ca(OH) 2 and FeSO 4, was initially studied using a continuously operated trickling filter. The system efficiency ranged up to 60–70% for a hydraulic loading of 1.1 m 3/m 2 day and up to 80–85% for a hydraulic loading 0.6 m 3/m 2 day. A stable chemical oxygen demand (COD) removal efficiency of 60–70% was achieved even in the case of undiluted wastewater at a hydraulic loading of 1.1 m 3/m 2 day. The effectiveness of biological treatment of a mixture of the company's main wastewater streams was also examined. The microorganisms developed in the trickling filter were able to efficiently remove COD levels up to 36,000 mg/L, under aerobic conditions at pH values between 5.5 and 8.0. Depending on the operating conditions of the system, about 30–60% of the total COD removal was attributed to air stripping caused by the air supply at the bottom of the filter, whereas the rest of the COD was clearly removed through biological action. The proposed biological treatment process based on a trickling filter, which was operated either continuously or even better in an SBR mode, appears as a promising pretreatment step for coping with dye manufacturing wastewaters in terms of removing a significant portion of the organic content.

Biological chromium(VI) reduction using a trickling filter

A pilot-scale trickling filter was constructed and tested for biological chromium(VI) removal from industrial wastewater. Indigenous bacteria from industrial sludge were enriched and used as inoculum for the filter. Sodium acetate was used as carbon source and it was found to inhibit chromate reduction at high concentrations. Three different operating modes were used to investigate the optimal performance and efficiency of the filter, i.e. batch, continuous and SBR with recirculation. The latter one was found to achieve removal rates up to 530 g Cr(VI)/m 2 d, while aeration was taking place naturally without the use of any external mechanical means. The low operating cost combined with the high hexavalent chromium reduction rates indicates that this technology may offer a feasible solution to a very serious environmental problem.

Induction of denitrification in a pilot-scale trickling filter by adding nitrate at high loading rate

Oxygen transferred from the liquid phase into a biofilm can be used for aerobic degradation of organic matter and for nitrification. A second possible pathway for the removal of organic matter is denitrification in anoxic zones deeper in the biofilm. At high organic loading rates with insufficient oxygen supply to the biofilm, denitrification could be induced by providing the biofilm with external nitrate. This possibility was tested in a pilot-scale trickling filter by adding a pulse of nitrate to a highly loaded trickling filter. The experiment showed that denitrification can indeed be induced by adding nitrate at high loading conditions and that this way a considerably increased substrate removal capacity can be obtained. The fact that denitrification occurred was confirmed by the increased production of CO2 from bioconversion processes, without a major change of the O2 consumption. The simplified mixed-culture biofilm model developed by Rauch et al. was extended for the description of off-gas measurements and was able to describe the results of the experiment very well.

A trickling filter application for the treatment of a gold milling effluent

Some industrial processes, such as plating and gold mining, utilise cyanide and related compounds in their operations. The resulting effluents contain cyanide, thiocyanate, and other toxic ions, which are noxious to the environment and require removal before effluent discharging. Several methods are available for cyanide removal and/or detoxification. Natural degradation, alkaline chlorination, and oxidation with hydrogen peroxide are the most frequently used methods in full-scale operations. However, there are technical and economical concerns related to these methods, which make biological treatment processes a feasible alternative. The use of a trickling filter is suitable for treating wastewaters with load variation. It is a simple system, is easy to operate, and presents low energy requirements. In this type of bioreactor, it is possible to retain microorganisms with a slow growth rate, such as those responsible for cyanide degradation. The present work reports the results obtained in a fixed bed bioreactor in which were evaluated: (a) the influence of the recirculation ratio (0 to 0.75), (b) the role of a biomass in cyanide removal, and (c) the biomass characteristics. The experiments were carried out in a continuous pilot scale trickling filter, 7.4 m high, packed with plastic rings of polypropylene. The experimental set-up consisted of two identical units, one of which was used for tests without biomass (abiotic tests). The reactors were fed with a mixture of synthetic gold milling effluent and sewage, and the treatment efficiency was evaluated through the monitoring of the following parameters: chemical oxygen demand (COD), free cyanide, thiocyanate, copper, iron and zinc concentrations. The results indicated that it was possible to remove more than 90% of the free cyanide, thiocyanate, copper and zinc originally found in the influent. These removal efficiencies were obtained when the pilot bioreactor was operated without recirculation, and moreover, higher recirculation ratio brought about a decreasing in the pH of the influent, lowering the efficiency of zinc removal. It was observed that the microbial activity was found to be responsible for thyocyanate degradation and copper removal. The tests carried out in the reactor without biomass showed that the percentage of free cyanide removed by volatilisation was low (22.6%), and even lower when recirculation did not take place (7.7%). This fact confirms the important role, which the biomass plays in the degradation of this pollutant.

Development of a Chemical Fate Model for Trickling Filters Based on the Activated Sludge Model SimpleTreat: A Case Study for LAS

A new chemical fate model for trickling filter wastewater treatment plants was developed, using the same principles as the steady-state nonequilibrium activated sludge model SimpleTreat, in combination with an existing biofilm model. To test the new model in detail, a pilot-scale (200 L) trickling filter was built and operated. Using this setup, removal of the surfactant LAS was measured under different well-characterized operating conditions. The new model could be fitted to data on LAS removal in the pilot-scale filter as well as in two full-scale domestic treatment plants. The same biodegradation rate coefficient (derived from activated sludge data) could be used in all cases, except for one laboratory experiment with higher LAS influent concentrations. It is concluded that the effect of high influent concentrations on the biodegradation rate should be further investigated.

Heating up trickling filters to tackle cold weather conditions

The investigated effects of heating the filling material in trickling filters were carried out at the Ingolstadt wastewater treatment plant, Germany. Two pilot scale trickling filters were set up. Heat exchanger pipings were embedded in the filter media of one of these trickling filters, and the temperature in the trickling filter was raised. The other trickling filter was operated under normal temperature conditions, and was used as a control. The results clearly demonstrate that the performance of trickling filters cannot be constantly improved by heating the biofilm support media. A sustained increase of the metabolic rates did not occur. The decrease of the solubility of oxgen in water and mass transfer limitations caused by an increase of the biofilm thickness are the main reasons for that. Thus, the heating of trickling filters (e.g. by waste heat utilization) in order to increase the capacity of trickling filters under cold weather conditions cannot be recommended.