Biofiltration Process Research Articles

Removal of micropollutants in biofilters: Hydrodynamic effects on biofilm assembly and functioning

Global water resources contain a variety of micropollutants (MPs), including pharmaceuticals, personal care products, and pesticides. This study investigated the removal of MPs during drinking water production by means of biofiltration. The objective of this work was to investigate the influence of hydrodynamics on biofilm growth and development in a biofiltration process and the consequent effect on MP biotransformation rates. We operated three groups of biofiltration columns continuously for 381 days under three distinct hydrodynamic regimes (superficial velocity: 10, 20, 40 cm h−1) and fed them a mixture of 29 micropollutants at low concentrations. Total protein concentrations were used as a surrogate measurement for attached biomass and periodic tracer experiments were conducted to estimate dispersivity and assess changes in the depth of the biological zone in each biofilter. These data revealed significant differences in biofilm assembly among the biofilters; higher superficial velocities led to less concentrated surface biomass but a deeper biological zone and more total biomass. Eleven of the 29 MPs were biotransformed and nine of those could be evaluated to estimate biotransformation rates. The second-order rate constants for all nine MPs were not significantly different among the hydrodynamic regimes. However, a depth-based analysis of biotransformation rates revealed significantly greater second-order rate constants for 5 of the MPs at increasing biofilter depths, suggesting that sparse microbial communities found in deeper and more oligotrophic biofilters had a greater activity for the biotransformation of these MPs. The identification of several transformation products at similar relative distributions suggests that the greater activity was not the result of changing metabolic processes under more oligotrophic conditions. These results improve our fundamental understanding of biofilm assembly and functioning in biofiltration processes.

COMPARATIVE STUDY OF NITROGEN BIOREMOVAL FROM AQUACULTURE WASTEWATER USING BIOFLOCS TECHNIQUE (BFT) VERSUS BIOFILTRATION SYSTEM

Laboratory experiment aimed to comparison between treatment of fish wastewater using biofloc technology (BFT)and biofilter system to re-use water and reduce its change periods. Ammonium concentration increased from 0.51 mg/l at beginning of experiment to 0.54 mg/l and decreased to 0.25 mg/l and is fixed at 0.49 mg/l for biofilter samples. While, these concentrations ware 0.62- 0.87-0.12-0.27 mg/l for biofloc treatment samples. Ammonium reduction ratio of biofilter was 32% versus 17.33% for biofloc technique at beginning of experiment then it still increasing and reached to 42 % for biofilter against 7.45% of biofloc technique. Unexpected decrease in the ammonium reduction ratio for biofilter system by 21.87 and 15.52% versus 62.50 and 53.45% correspondingly for biofloc. These results were referred to biofiltration process adaptation and lack of uniformity of bioflocs throughout whole water tank. Results of measured ammonium concentrations show superiority of the use of biofloc technique over biofilter system. The decline in nitrite reduction ratio for biofilter of 63.16% at the second week of the start of experiment happened and then there was a slight increase in nitrite reduction ratio 63.49% to be settled on the 65% reduction ratio value. This was referred to biofilter clogging and biomass accumulation. Biofloc technique demonstrated an excessive superiority (93.02%) in nitrite reduction ratio at beginning of the experiment over biofilter system (70.54%). Two systems had similar behavior of nitrite reduction ratio throughout the rest of experiment. Finally, use of BFT systems to freshwater tilapia aquaculture benefits both the reduction in ammonium and nitrite concentrations and can be effective in improvement fish production.

Removal of traces of toluene and p-xylene in indoor air using biofiltration and a hybrid system (biofiltration + adsorption).

Biofiltration technology and the hybrid system combining biofiltration and adsorption (onto activated carbon) were compared as possible methods to toluene and p-xylene at parts per million concentration levels (2-45 and 1-33ppb, respectively). An organic material was used as packing material for the biofiltration process. Even at low empty bed residence times (EBRTs) and concentrations, toluene removal efficiency reached 100% and p-xylene showed an increasing trend on their removal efficiency over the time using biofiltration. The assessment of by-products and particle generation by the biofilter and the hybrid system were taken into account. Acetone and acetic acid were identified as by-products of the biofilter. Particle emissions in the range of 0.03 to 10μm were recorded for both systems.

Comparison of heterotrophic and autotrophic denitrification processes for treating nitrate-contaminated surface water.

The goal of this study was to compare the nitrogen removal rate, effluent algal growth potential (AGP), nitrous oxide (N2O) emissions and global warming potential (GWP) between two laboratory-scale bioreactors: the autotrophic denitrification biofilter (ADBF) and heterotrophic denitrification biofilter (HDBF) for treating nitrate-contaminated surface water. The comparative study of nitrogen removal rate between ADBF and HDBF was conducted by a long-term experiment, and the comparative study of the effluent AGP, N2O emissions and GWP between ADBF and HDBF were carried out by the corresponding batch tests. The results show that the heterotrophic and autotrophic denitrification rates were close to each other. Besides, the AGP of the ADBF effluent was 2.08 times lower than that of the HDBF effluent, while the N2O concentration in off-gas emitted from HDBF was 6-8 times higher than that from ADBF. The higher N2O-N emission rate of HDBF was mainly responsible for the higher GWP of HDBF than that of ADBF. Furthermore, with a novel light-weight filtration media (NLWFM) for filtration, the autotrophic denitrification (ADN) process combined with biofilter process would be the optimal denitrification process for nitrogen removal from nitrate-contaminated surface water. The study also provided a systematic method for evaluation of biological nitrogen removal (BNR) process.

Modelling of a biofiltration process of volatile organic compound mixtures in a biofilter

ABSTRACTCurrently, different methods for air clean-up from chemical pollutants are applied worldwide: adsorption, absorption, and thermal and catalytic oxidation. One of the most promising methods is biological air cleaning. The aim of this study was to test the performance of a developed biofilter with packing material of activated pine bark for biological air cleaning and to mathematically model the biofiltration processes. Comparative analysis of the modelling results for individual pollutants (butyl acetate, butanol and xylene) showed strongest dependence of the efficiency of xylene removal from the air on the amount and ratio of other substances (from 20% to 70%). Thus, the process of removal of pollutants (butanol and butyl acetate) that are easier to biologically decompose was obtained to be influenced to a lesser extent by the amount and ratio (%) of other components. The results also showed that the efficiency of butyl acetate removal mostly depended on the ratio of other substances in the mixture (from 15% to 100%), whereas the efficiency of butyl acetate and xylene removal mostly depended on the amount of other substances in the mixture (from 20% to 100%). With the parameters of the biofilter (height of packing material, incoming air flow velocity) and the pollutants to be removed known, the mathematical expression of the filter efficiency was found, which would allow to make theoretical calculation and selection of the most appropriate parameters of the device as well as to achieve maximum efficiency of air cleaning.

Pilot investigation of two-stage biofiltration for removal of natural organic matter in drinking water treatment

A pilot study employing two parallel trains of two-stage biofiltration, i.e., a sand/anthracite (SA) biofilter followed by a biologically-active granular activated carbon (GAC) contactor, was conducted to test the efficiency, feasibility and stability of biofiltration for removing natural organic matter (NOM) after coagulation in a drinking water treatment plant. Results showed the biofiltration process could effectively remove turbidity (<0.1 NTU in all effluents) and NOM (>24% of dissolved organic carbon (DOC), >57% of UV254, and >44% of SUVA254), where the SA biofilters showed a strong capacity for turbidity removal, while the GAC contactors played the dominant role in NOM removal. The vertical profile of water quality in the GAC contactors indicated the middle-upper portion was the critical zone for the removal of NOM, where relatively higher adsorption and enhanced biological removal were afforded. Fluorescence excitation-emission matrix (EEM) analysis of NOM showed that the GAC contactors effectively decreased the content of humic-like component, while protein-like component was refractory for the biofiltration process. Nutrients (NH4-N and PO4-P) supplementation applied upstream of one of the two-stage biofiltration trains (called engineered biofiltration) stimulated the growth of microorganisms, and showed a modest effect on promoting the biological removal of small non-aromatic compositions in NOM. Redundancy analysis (RDA) indicated influent UV254 was the most explanatory water quality parameter for GAC contactors’ treatment performance, and a high load of UV254 would result in significantly reduced removals of UV254 and SUVA254.

Ability of the marine bacterium Pseudomonas fluorescens BA3SM1 to counteract the toxicity of CdSe nanoparticles

In the marine environment, bacteria from estuarine and coastal sediments are among the first targets of nanoparticle pollution; it is therefore relevant to improve the knowledge of interactions between bacteria and nanoparticles. In this work, the response of the marine bacterium Pseudomonas fluorescens BA3SM1 to CdSe nanocrystals (CdSe NPs) of 3nm (NP3) and 8nm (NP8) in diameter was evaluated through microscopic, physiological, biochemical and proteomic approaches. Transmission electron microscopy images showed that NP3 were able to penetrate the bacteria, while NP8 were highly concentrated around the cells, embedded in large exopolysaccharides. In our experimental conditions, both CdSe NP sizes induced a decrease in respiration during the stationary growth phase, while only NP8 caused growth retardation and a decrease in pyoverdine production. Proteomic analyses highlighted that the strain responded to CdSe NP toxicity by inducing various defence mechanisms such as cell aggregation, extracellular CdSe NP sequestration, effective protection against oxidative stress, modifications of envelope organization and properties, and cadmium export. In addition, BA3SM1 presented a biosorption capacity of 1.6×1016NP3/g dry weight and 1.7×1015NP8/g dry weight. This strain therefore appears as a promising agent for NP bioremediation processes. Proteomic data are available via ProteomeXchange with identifier PXD004012. Biological significanceTo the best of our knowledge, this is the first report focussing on the effects of CdSe colloidal nanocrystals (CdSe NPs) on a marine strain of Pseudomonas fluorescens. CdSe NPs are extensively used in the industry of renewable energies and it is regrettably expected that these pollutants will sometime soon appear in the marine environment through surface runoff, urban effluents and rivers. Bacteria living in estuarine and coastal sediments will be among the first targets of these new pollutants. The pseudomonads are frequently found in these ecosystems. They are involved in several biogeochemical cycles and are known for their high resistance to pollutants. Consequently, this study focussing on the effects of CdSe NPs on the marine strain P. fluorescens BA3SM1 is highly relevant for several reasons. First, it aims at improving knowledge about the interactions between bacteria and NPs. This is fundamental to effectively use NPs against pathogenic bacteria. Secondly, in spite of CdSe NP interactions with the bacterial cells, the strain BA3SM1 can develop various strategies to counteract CdSe NP toxicity and ensure its growth. It exhibits interesting properties to sequester CdSe NPs and it retains its ability to form biofilm. The strain therefore appears as a promising agent for NP bioremediation thanks to biofiltration processes. Finally, this study shows that CdSe NPs of 8nm in diameter cause a decrease in the secretion of siderophore pyoverdine, a secondary metabolite playing a key role in microbial ecology since it drives bacterial survival and competitiveness in ecosystems. Bacteria producing effective siderophores survive better in a Fe-deficient environment where they antagonize the growth of other microbes thought iron deprivation. Furthermore, siderophores are also employed as virulence factors in human pathogenic strains such as P. aeruginosa. Consequently, this study highlights that NPs can impact the secondary metabolism of bacteria with environmental and medical implications.In addition, in this work, Data-Dependant Acquisition (DDA) provided state of the art Mass Spectrometry data by Spectral Counting and MS1 Label-Free. The combination of these two well-known proteomic techniques including manual validations strengthened the identification and quantification of regulated proteins. Moreover, numerous correlations between proteomic analyses and other observations (physiological, biochemical, microscopic) consolidated our interpretations.

Lessons from the “Living-Filter”: An in-reservoir floating treatment wetland for phytoplankton reduction prior to a water treatment works intake

The Living-Filter is a novel floating emergent treatment wetland design that combines a hydroponic plant-bed with curtains and baffles. Thames Water Utilities and AquaticEngineering UK designed and installed the Living-Filter in Farmoor II reservoir, Oxfordshire, UK, in July 2012. The aim is to reduce the phytoplankton biomass prior to the water treatment works intake. The plant-bed (1mH×21mW×10mL) supports plants of Phragmites australis, Phalaris arundinacea and Carex acutiformis, with a combined system of curtains and baffles that aid the water to flow through the Living-Filter. All the water treated at the water treatment works has passed through the Living-Filter. The roots and a plastic fabric increase the surface area for biofiltration processes and the rhizosphere provides refuge for zooplankton. The research attempts to answer the question: Can the Living-Filter be used as an in-reservoir pre-treatment filtration process for reducing the phytoplankton biomass onto the water treatment works? Weekly surveys were carried out from July to October 2013 at sixteen sampling sites to measure physico-chemical and biological variables. The results for the first year of study show: (1) Soluble manganese, dissolved inorganic nitrogen and nitrites were significantly lower after treatment through the Living-Filter. (2) Chlorophyll-a removal efficiency was up to 45% during the first seven weeks. (3) Zooplankton abundance was more stable within the rhizosphere than in the water column. (4) The aerial shoots of the plants developed well, but based on root development only Phalaris and Carex should be considered for future designs. This work highlights the potential of the Living-Filter for phytoplankton reduction, but it also addresses questions that will further improve the system.

Coupling biofiltration process and electrocoagulation using magnesium-based anode for the treatment of landfill leachate

In this research paper, a combination of biofiltration (BF) and electrocoagulation (EC) processes was used for the treatment of sanitary landfill leachate. Landfill leachate is often characterized by the presence of refractory organic compounds (BOD/COD < 0.13). BF process was used as secondary treatment to remove effectively ammonia nitrogen (N-NH4 removal of 94%), BOD (94% removed), turbidity (95% removed) and phosphorus (more than 98% removed). Subsequently, EC process using magnesium-based anode was used as tertiary treatment. The best performances of COD and color removal from landfill leachate were obtained by applying a current density of 10 mA/cm2 through 30 min of treatment. The COD removal reached 53%, whereas 85% of color removal was recorded. It has been proved that the alkalinity had a negative effect on COD removal during EC treatment. COD removal efficiencies of 52%, 41% and 27% were recorded in the presence of 1.0, 2.0 and 3.0 g/L of sodium bicarbonate (NaHCO3), respectively. Hydroxide ions produced at the cathode electrode reacted with the bicarbonate ions to form carbonates. The presence of bicarbonates in solution hampered the increase in pH, so that the precipitation of magnesium hydroxides could not take place to effectively remove organic pollutants.

Simultaneous removal of ammonia and hydrogen sulfide gases using biofilter media from the biodehydration stage and curing stage of composting.

Biofiltration of NH3 and H2S with different packing media, biodehydration stage compost (BSC), and curing stage compost (CSC) was studied. Meanwhile, fluorescence excitation-emission matrix (EEM) spectroscopy was used to characterize the conversion mechanisms of organic matter during these biofiltration processes. Both biofilters were effective for the simultaneous removal of NH3 and H2S when inlet concentrations of NH3 and H2S were 0-50 and 50-250mg/m3, respectively. An abrupt increase in the inlet gas concentrations of NH3 and H2S to 100-150 and 200-250mg/m3, respectively, caused the decrease in the removal efficiencies (REs) of NH3 and H2S in the BSC biofilter, followed by a slow upturn. By contrast, relatively steady REs of both NH3 and H2S were observed in the CSC biofilter. After 60days of operation, the average REs of NH3 and H2S were more than 95% in the CSC biofilter. During the operation of CSC, nitrate and nitrite peaked around the 30th day, whereas sulfate showed a steady increase. The excitation-emission matrix fluorescence and parallel factor analysis (EEM-PARAFAC) indicated that the simultaneous inlet of NH3 and H2S facilitated the degradation of protein-like substances, whereas humic-like substances played an important role in the packing filters for the treatment of the two odorous pollutants.

Impact of formaldehyde and VOCs from waste treatment plants upon the ambient air nearby an urban area (Spain)

Emission factors of formaldehyde and VOCs were determined for two waste treatment plants (WTP) located in the metropolitan area of Barcelona city. Formaldehyde emission factors were determined from the biogas engines exhausts and the process chimneys (after the biofilter process), and VOC emission factors were determined in the process chimneys. Formaldehyde and VOC were dynamically sampled using DNPH-coated adsorbent tubes with ozone scrubber and multi-sorbent bed tubes (Carbotrap, Carbopack X and Carboxen 569), respectively, using portable pump equipment. Formaldehyde emission factors from biogas engines were found between 0.001–0.04gs−1. Additionally, formaldehyde and VOC emission factors from process chimneys were found to be between 0.0002–0.003gs−1 and 0.9±0.3gs−1, respectively. Employing real emission factors, the expected concentrations derived from the WTPs in their nearby urban areas were calculated using The Atmospheric Pollution Model (TAPM, CSIRO), and impact maps were generated. On the other hand, ambient air formaldehyde and VOC concentrations were determined in selected locations close to the evaluated waste treatment facilities using both active and passive samplers, and were between 2.5±0.4–5.9±1.0μgm-3 and 91±48–242±121μgm-3, respectively. The concentrations of formaldehyde and VOC derived exclusively from the waste treatment plants were around 2% and 0.3±0.9% of the total formaldehyde and VOC concentrations found in ambient air, respectively.

A novel anoxic-aerobic biofilter process using new composite packing material for the treatment of rural domestic wastewater.

A pilot scale experiment was conducted to evaluate the characteristics of contaminants removal in a continuously two-stage biological process composed of an anoxic biofilter (AF) and an biological aerated filter (BAF). This novel process was developed by introducing new composite packing material (MZF) into bioreactors to treat rural domestic wastewater. A comparative study conducted by the same process with ceramsite as packing material under the same conditions showed that a MZF system with a Fe proportion in the packing material performed better in chemical oxygen demand (COD) removal (average 91.5%), ammonia (NH4(+)-N) removal (average 98.3%), total nitrogen (TN) removal (average 64.8%) and total phosphorus (TP) removal (average 90%). After treatment of the MZF system, the concentrations of COD, NH4(+)-N, TN and TP in effluent were 20.3 mg/L, 0.5 mg/L, 11.5 mg/L and 0.3 mg/L, respectively. The simultaneously high efficiencies of nitrification, denitrification and phosphorus removal were achieved by the coupling effects of biological and chemical processes in the MZF system. The results of this study showed that the application of MZF might be a favorable choice as packing material in biofilters for treatment of rural domestic wastewater.

Application of a hybrid biofilter column for the removal of Cr(VI) from aqueous solution using an indigenous bacterial strain Pseudomonas taiwanensis

ABSTRACTIn the present study, a laboratory-scale biofilter column was designed and fabricated. It was packed with a mixture of coal and compost as a packing medium. The column was enriched with an indigenous bacterial strain Pseudomonas taiwanensis isolated from aerobic mixed culture of Sewage Treatment Plant, BITS-Pilani, Pilani campus. The removal of hexavalent chromium [Cr(VI)] from aqueous solution was investigated in the biofilter column. The entire biofiltration operation was divided into five phases (I to V) for a period of 63 days. Biofilter column was subjected to shock loading conditions for 20 days immediately after 63 days of operation. The maximum removal efficiency of 89.4% was obtained during phase V for Cr(VI) inlet concentration of 40 mg L−1. During shock loading, maximum removal efficiency was obtained as 90% for 48.5–50 mg L−1 of initial Cr(VI) concentration. Kinetic parameters of biofiltration process for Cr(VI) removal were also determined by fitting Michaelis-Menten kinetic model with experimental data. The Michaelis-Menten kinetic constants were obtained as 0.258 mg L−1 min−1 and 26.83 mg L−1. It was found that Ottengraf-Van den Oever model with zero-order diffusion limitation fit the experimental data quite well for phases III, IV, and V with coefficient of determination (R2) values .97, .99, and .984, respectively. A possible method for safe disposal of packing medium was also presented in this study.

Recent Progress in Slow Sand and Alternative Biofiltration Processes

Slow sand filtration is typically cited as being the first “engineered” process in drinking-water treatment. Proven modifications to the conventional slow sand filtration process, the awareness of induced biological activity in riverbank filtration systems, and the growth of oxidant-induced biological removals in more rapid-rate filters (e.g. biological activated carbon) demonstrate the renaissance of biofiltration as a treatment process that remains viable for both small, rural communities and major cities. Biofiltration is expected to become even more common in the future as efforts intensify to decrease the presence of disease-causing microorganisms and disinfection by-products in drinking water, to minimize microbial regrowth potential in distribution systems, and where operator skill levels are emphasized.Recent Progress in Slow Sand and Alternative Biofiltration Processes provides a state-of-the-art assessment on a variety of biofiltration systems from studies conducted around the world. The authors collectively represent a perspective from 23 countries and include academics, biofiltration system users, designers, and manufacturers.It provides an up-to-date perspective on the physical, chemical, biological, and operational factors affecting the performance of slow sand filtration (SSF), riverbank filtration (RBF), soil-aquifer treatment (SAT), and biological activated carbon (BAC) processes. The main themes are: comparable overviews of biofiltration systems; slow sand filtration process behavior, treatment performance and process developments; and alternative biofiltration process behaviors, treatment performances, and process developments.This title belongs to Water Research Foundation Report SeriesISBN: 9781843391203 (Print)ISBN: 9781780402451 (eBook)

Modeling the improvement of ultrafiltration membrane mass transfer when using biofiltration pretreatment in surface water applications

In surface water treatment, ultrafiltration (UF) membranes are widely used because of their ability to supply safe drinking water. Although UF membranes produce high-quality water, their efficiency is limited by fouling. Improving UF filtrate productivity is economically desirable and has been attempted by incorporating sustainable biofiltration processes as pretreatment to UF with varying success. The availability of models that can be applied to describe the effectiveness of biofiltration on membrane mass transfer are lacking. In this work, UF water productivity was empirically modeled as a function of biofilter feed water quality using either a quadratic or Gaussian relationship. UF membrane mass transfer variability was found to be governed by the dimensionless mass ratio between the alkalinity (ALK) and dissolved organic carbon (DOC). UF membrane productivity was optimized when the biofilter feed water ALK to DOC ratio fell between 10 and 14.

A combined upflow anaerobic sludge bed and trickling biofilter process for the treatment of swine wastewater

ABSTRACTA combined upflow anaerobic sludge blanket (UASB)-trickling biofilter (TBF) process was constructed to treat swine wastewater, a typical high-strength organic wastewater with low carbon/nitrogen ratio and ammonia toxicity. The results showed that the UASB-TBF system can remarkably enhance the removal of pollutants in the swine wastewater. At an organic loading rate of 2.29 kg/m3 d and hydraulic retention time of 48 h in the UASB, the chemical oxygen demand (COD), Suspended Solids and Total Kjeldahl Nitrogen removals of the combined process reached 83.6%, 84.1% and 41.2%, respectively. In the combined system the UASB served as a pretreatment process for COD removal while nitrification and denitrification occurred only in the TBF process. The TBF performed reasonably well at a surface hydraulic load as high as 0.12 m3/m2 d. Since the ratio of influent COD to total mineral nitrogen was less than 3.23, it is reasonable to suggest that the wood chips in TBF can serve as a new carbon source for denitrification.

Toxicity decrease in urban wastewaters treated by a new biofiltration process

We carried out a project aimed to evaluate the possible role played by the freshwater zebra mussel (Dreissena polymorpha) in the possible decrease of some environmental pollutants recalcitrant to tradition wastewater treatments. By the help of a pilot-plant built in the largest wastewater treatment plant of Milan (Italy), we tested several waste mixtures in order to measure the chemicals' abatement made by mussels' biofiltration. This study represents the last step of the wider project and it aimed to evaluate if the decrease in the concentration of some urban pollutants measured in wastewaters was followed by a corresponding toxicity reduction. Thus, we performed 7-day exposures under laboratory conditions to test the toxicity of the raw wastewaters and those preliminary filtered by zebra mussels, through the measurement of different end-points of acute and chronic toxicity. Results showed a clear positive effect of mussels' biofiltration mainly to decrease the acute toxicity made by the two tested wastewater mixtures, while the biomarkers' suite used to evaluate the chronic toxicity showed contradictory results.

A hybrid process of biofiltration of secondary effluent followed by ozonation and short soil aquifer treatment for water reuse

The Shafdan reclamation project facility (Tel Aviv, Israel) practices soil aquifer treatment (SAT) of secondary effluent with hydraulic retention times (HRTs) of a few months to a year for unrestricted agricultural irrigation. During the SAT, the high oxygen demand (>40 mg L−1) of the infiltrated effluent causes anoxic conditions and mobilization of dissolved manganese from the soil. An additional emerging problem is the occurrence of persistent trace organic compounds (TrOCs) in reclaimed water that should be removed prior to reuse. An innovative hybrid process based on biofiltration, ozonation and short SAT with ∼22 d HRT is proposed for treatment of the Shafdan secondary effluent to overcome limitations of the existing system and to reduce the SAT's physical footprint. Besides efficient removal of particulate matter to minimize clogging, coagulation/flocculation and filtration (5–6 m h−1) operated with the addition of hydrogen peroxide as an oxygen source efficiently removed dissolved organic carbon (DOC, to 17–22%), ammonium and nitrite. This resulted in reduced effluent oxygen demand during infiltration and oxidant (ozone) demand during ozonation by 23 mg L−1 and 1.5 mg L−1, respectively. Ozonation (1.0–1.2 mg O3 mg DOC−1) efficiently reduced concentrations of persistent TrOCs and supplied sufficient dissolved oxygen (>30 mg L−1) for fully oxic operation of the short SAT with negligible Mn2+ mobilization (<50 μg L−1). Overall, the examined hybrid process provided DOC reduction of 88% to a value of 1.2 mg L−1, similar to conventional SAT, while improving the removal of TrOCs and efficiently preventing manganese dissolution.

Effectiveness of a multi-stage biofilter approach at pilot scale to remove odor and vocs

This paper describes an experience conducted to evaluate the performances of a multi-stage approach using a biofiltration process applied to treat exhaust air. In particular, the experimentation was carried out using a pilot plant for the biofiltration of exhaust air from a solid recovered fuel drying process treating the dry fraction of municipal solid waste. Such exhaust streams are characterized by low concentrations of volatile organic compounds and high presence of odorous compounds, such as H 2 S and NH 3 . The adopted layout for the experimentation was a multi-stage plant. Each of the two stages (biotrickling filters) used seashells as packing material. In particular, the choice of seashell was defined after the evaluation of the hydrody namic behavior of different packing materials at the same running conditions. Moreover, some velocity measurements were conducted with the aim at improving the geometry of the reactors and the fan sizing. The multi-stage biofiltration performances indicate that the solutions are suitable as well as applicable for use in industrial plants.

Effect of biofiltration process on the control of THMs and HAAs in drinking water

Natural organic matter (NOM) is the precursor of disinfection by-product (DBP) formation potential. In this study, the aim was to investigate NOM removal and chlorinated DBP reduction by the biofiltration process. Different materials (zeolite, sand, and granular activated carbon (GAC)) and contact time effects were evaluated by feeding Porsuk water (PW) from Eskisehir, Turkey. The reduction performances of trihalomethane formation potential (THMFP) and haloacetic acid formation potential (HAAFP) were higher in the GAC column than in the sand and zeolite columns. The GAC biofilter column removed 64% of dissolved organic carbon (DOC), and therefore, THMFP and HAAFP were decreased by about 68 and 64% in 30 min. The zeolite and sand biofilter columns only reduced HAAFP by 27 and 21%, respectively.