Biodegradable Organic Matter Removal Research Articles

DOM chemodiversity pierced performance of each tandem unit along a full-scale “MBR+NF” process for mature landfill leachate treatment

Mature landfill leachate contains a substantial fraction of recalcitrant dissolved organic matters (DOM) that is a challenging for conventional wastewater treatment that is typically focused on the removal of biodegradable organic matter. “Biological treatment + membrane treatment” has been widely employed to treat complex leachate. However, the performance of each unit based on both conventional bulk indicators and molecular information has not been well understood. Therefore, the fate of DOM chemodiversity along the full-scale treatment process across ten sampling points over three different seasons were analyzed to determine the efficiency of every unit process with the assistance of ultra-performance liquid chromatography coupled with hybrid quadrupole Orbitrap mass spectrometry. Results showed that the process performance, visualized through the molecular signals, were relatively stable in the temporal dimension. The process removed 83.2%-92.2% of DOM molecules in terms of richness, where lignin/carboxyl-rich alicyclic compounds (CRAM)-likes with relatively high saturation was preferentially removed, while newly generated bio-derived N-containing compounds (N/Cwa 0.15-0.17) became resistant. The relationship between conventional bulk physicochemical indicators and molecular indexes suggested that soluble chemical oxygen demand (sCOD) and dissolved organic carbon (DOC) were contributed by the refractory DOM with high weighted average double bond equivalents (DBEwa), which was distributed in the region of O/C 0.2-0.5 and H/C 1.2-1.8. This refractory DOM required ultrafiltration and nanofiltration for removal. DOM molecules were positively correlated with five-day biochemical oxygen demand (BOD5) and revealed that approximately 96.9%-98.4% of the DOM could be removed or transformed in the primary anoxic zone. In addition, the bio-derived aliphatic/proteins, lipids and lignin/CRAM-likes (O/C > 0.2) with condensed aromatization were the sources of dissolved organic nitrogen (DON) and still remained in the final effluent. The present study suggests that the design and operation of the combination process with biological and membrane treatment could be specifically optimized based on the DOM molecular characteristics of the wastewater.

TECNOLOGIAS EMPREGADAS NO TRATAMENTO DE EFLUENTES DE LATICÍNIOS DO VALE DO RIO BRAÇO DO NORTE - SC

Associada à atividade produtiva de laticínios está o grande montante de efluentes gerados no processo de beneficiamento do leite. Pela complexidade de composição, variação nas taxas de produção e variação na própria composição do efluente gerado nesta atividade, a escolha de um sistema eficaz na remoção dos contaminantes ali presentes pode ser bastante complexa. Desta forma, com o presente estudo buscou-se apresentar as técnicas utilizadas em escala global para essa finalidade, e paralelamente traçar um perfil das tecnologias aplicadas pelas empresas de laticínios na região do Vale do rio Braço do Norte, sul de Santa Catarina, bem como demais aspectos relacionados à gestão ambiental dessas empresas. Após levantamento de dados, por meio de pesquisa de campo via questionário e avaliação documental, observou-se que as empresas dessa região aplicam predominantemente sistemas anaeróbios para remoção de matéria orgânica biodegradável, atingindo níveis de remoção dentro da legislação. Contudo, demais parâmetros analisados, como óleos e graxas, pH e sólidos sedimentáveis apresentaram alguns valores fora do preconizado pelos órgãos ambientais. A gestão ambiental das empresas é realizada predominantemente por pessoal terceirizado, deixando evidente a falta de pessoal interno, tecnicamente capacitado para atuar nas empresas.

Study on the removal of biodegradable NOM from seawater using biofiltration

Despite the low biodegradability of seawater NOM, problems associated with biofouling are common in facilities that handle seawater. In this work, a fixed-film aerobic biofilter is proposed as an effective unit for preventing biofouling in such facilities.A packed-bed biofilter with an EBCT=6–11min was employed. The results demonstrated that the DOC is reduced by 6% and the BOD7 is reduced up to 15%. The LC-OCD analysis revealed that biofiltration abates the LMW neutrals and biopolymer fractions by 33 and 17%, respectively. However, the fractionation with UF membrane showed that the biofiltration process is able to degrade the more biodegradable compounds that have molecular weights that are greater than 1kDa and compounds with molecular weights of less than 1kDa.After biofiltration, the biological activity measured in terms of ATP removal was reduced by 60%. Finally, a test to evaluate the biofilm formation capacity of a water sample revealed reductions of ~94% when comparing biofiltered and non-biofiltered seawater. Therefore, a fixed-film aerobic biofiltration process could be a useful treatment for the removal of biodegradable organic matter from seawater and for improving the water quality in terms of less biofilm formation capacity.

Microbial Community Composition of Polyhydroxyalkanoate-Accumulating Organisms in Full-Scale Wastewater Treatment Plants Operated in Fully Aerobic Mode

The removal of biodegradable organic matter is one of the most important objectives in biological wastewater treatments. Polyhydroxyalkanoate (PHA)-accumulating organisms (PHAAOs) significantly contribute to the removal of biodegradable organic matter; however, their microbial community composition is mostly unknown. In the present study, the microbial community composition of PHAAOs was investigated at 8 full-scale wastewater treatment plants (WWTPs), operated in fully aerobic mode, by fluorescence in situ hybridization (FISH) analysis and post-FISH Nile blue A (NBA) staining techniques. Our results demonstrated that 1) PHAAOs were in the range of 11–18% in the total number of cells, and 2) the microbial community composition of PHAAOs was similar at the bacterial domain/phylum/class/order level among the 8 full-scale WWTPs, and dominant PHAAOs were members of the class Alphaproteobacteria and Betaproteobacteria. The microbial community composition of α- and β-proteobacterial PHAAOs was examined by 16S rRNA gene clone library analysis and further by applying a set of newly designed oligonucleotide probes targeting 16S rRNA gene sequences of α- or β-proteobacterial PHAAOs. The results demonstrated that the microbial community composition of PHAAOs differed in the class Alphaproteobacteria and Betaproteobacteria, which possibly resulted in a different PHA accumulation capacity among the WWTPs (8.5–38.2 mg-C g-VSS−1 h−1). The present study extended the knowledge of the microbial diversity of PHAAOs in full-scale WWTPs operated in fully aerobic mode.

Modeling and process evaluation of membrane bioreactor for removing biodegradable organic matter from water

A membrane bioreactor (MBR) process was employed for removing biodegradable organic matter (BOM) and ozonation disinfection byproducts (DBPs) exemplified by total aldehydes from ozonated potable water. The BOM removal was to prevent or reduce microbial regrowth in water distribution systems and to reduce DBP forming potential after ozonation. A mathematical modeling approach was used as a tool for performance prediction and process design with implication to process upscaling. The modeling protocol integrated adsorption and biodegradation in liquid and adsorbent phases with model parameters obtained from independent experiments. The BOM was expressed as biodegradable dissolved organic carbon (BDOC), assimilable organic carbon (AOC), and total aldehydes. The MBR studies demonstrated the process effectiveness in removing AOC, BDOC and total aldehydes, and validated the model's predictive capability. Sensitivity studies qualitatively evaluated parameters influencing process dynamics. The simulation studies were unique in examining shutdown and startup effects on process dynamics and process recovery.

Biofiltration for removal of BOM and residual ammonia following control of bromate formation

Nitrification was developed within a biological filter to simultaneously remove biodegradable organic matter (BOM) and residual ammonia added to control bromate formation during the ozonation of drinking water. Testing was performed at pilot-scale using three filters containing sand and anthracite filter media. BOM formed during ozonation (e.g., assimilable organic carbon (396–572 μg/L), formaldehyde (11–20 μg/L), and oxalate (83–145 μg/L)) was up to 70% removed through biofiltration. Dechlorinated backwash water was required to develop the nitrifying bacteria needed to convert the residual ammonia (0.1–0.5 mg/L NH 3-N) to nitrite and then to nitrate. Chlorinated backwash water resulted in biofiltration without nitrification. Deep-bed filtration (empty-bed contact time (EBCT)=8.3 min) did not enhance the development of nitrification when compared with shallow-bed filtration (EBCT=3.2 min). Variable filtration rates between 4.8 and 14.6 m/h (2 and 6 gpm/sf) had minimal impact on BOM removal. However, conversion of ammonia to nitrite was reduced by 60% when increasing the filtration rate from 4.8 to 14.6 m/h. The results provide drinking water utilities practicing ozonation with a cost-effective alternative to remove the residual ammonia added for bromate control.

Effects of Media, Backwash, and Temperature on Full‐Scale Biological Filtration

Full‐scale biofiltration experiments demonstrated that good removal of biodegradable organic matter (BOM) following ozonation could be achieved without compromising particle removal. BOM removal by granular activated carbon (GAC) filter adsorbers and dual‐media filters was measured using total organic carbon (TOC) and certain BOM components (carboxylic acids). The authors investigated how filter backwashing with water, water and air scour, and water and air scour at collapse‐pulsing conditions affect filter biomass, BOM removal, and particle removal. At 21‐24°C, the media type did not affect BOM removal. At 1‐3°C, GAC provided substantially better removal of oxalate and TOC than did anthracite. For both media types, cold water oxalate removals were significantly impaired, compared with those achieved in warm waters. BOM removal was more resilient than particle removal to changes in backwash protocol. Phospholipid biomass concentration was not directly related to BOM removal by filters.

Effects of Conventional Treatment on AOC and BDOC Levels

A 12‐month assimilable organic carbon (AOC) survey of 64 conventional water treatment plants was conducted to assess mechanisms affecting effluent AOC levels. The effect of conventional treatment steps (i.e., oxidation, coagulation, filtration, disinfection) on the formation or removal of biodegradable organic matter (BOM) was also investigated at six of the sites. BOM levels were increased or decreased by various factors including the type of filter media, the type of coagulant used, and the level of watershed protection of the plant's source water. Systems that prechlorinated and used anthracite/sand filtration generally had low removal of dissolved organic carbon (DOC) and biodegradable DOC (BDOC) and increases in AOC levels through the treatment process. Systems combining prechlorination and granular activated carbon (GAC) filtration showed increases in AOC in the settled water but removal of AOC through filtration. DOC and BDOC levels were generally reduced by conventional sand/GAC filtration.

Treatment of a colored groundwater by ozone-biofiltration: pilot studies and modeling interpretation

Pilot studies investigated the fates of color, dissolved organic carbon (DOC), and biodegradable organic matter (BOM) by the tandem of ozone plus biofiltration for treating a source water having significant color (50 cu) and DOC (3.2 mg/l). Transferred ozone doses were from 1.0 to 1.8 g O 3/g C. Rapid biofilters used sand, anthracite, or granular activated carbon as media with empty-bed contact time (EBCT) up to 9 min. The pilot studies demonstrated that ozonation plus biofiltration removed most color and substantial DOC, and increasing the transferred ozone dose enhanced the removals. For the highest ozone dose, removals were as high as 90% for color and 38% for DOC. While most of the color removal took place during ozonation, most DOC removal occurred in the biofilters, particularly when the ozone dose was high. Compared to sand and anthracite biofilters, the GAC biofilter gave the best performance for color and DOC removal, but some of this enhanced performance was caused by adsorption, since the GAC was virgin at the beginning of the pilot studies. Backwashing events had no noticeable impact of the performance of the biofilters. The Transient-State, Multiple-Species Biofilm Model (TSMSBM) was used to interpret the experimental results. Model simulations show that soluble microbial products, which comprised a significant part of the effluent BOM, offset the removal of original BOM, a factor that kept the removal of DOC relatively constant over the range of EBCTs of 3.5–9 min. Although improved biofilm retention, represented by a small detachment rate, allowed more total biofilm accumulation and greater removal of original BOM, it also caused more release of soluble microbial products and the build up of inert biomass in the biofilm. Backwashing had little impact on biofilter performance, because it did not remove more than 25% of the biofilm under any condition simulated.

Factors Affecting Drinking Water Biofiltration

This research examined several important factors affecting the removal of biodegradable organic matter in drinking water biofilters. Laboratory‐scale biofilters were used and were fed a cocktail of easily biodegradable compounds. The factors investigated were chlorine or chloramine in the backwash water, air scour during backwashing, anthracite/sand versus granular activated carbon (GAC)/sand media, and low (5°C) versus high (20°C) temperature operation. Factorial design experiments showed that the three main factors (chlorine in the backwash water, temperature, and media type) and their interactions were significant in most cases. The temperature effect was more significant when chlorine was present. The GAC filters were much more resistant to chlorinated backwash water than were anthracite filters. Air‐scour effects were generally negligible except in some cases at low temperature with chloramine in the backwash water. Glyoxal removal was more sensitive to unfavorable biofiltration conditions than were removals of acetate, formate, and formaldehyde.

Removal of Easily Biodegradable Organic Compounds by Drinking Water Biofilms: Analysis of Kinetics and Mass Transfer

This paper evaluates the rate of utilization of easily biodegradable organic compounds by drinking water biofilms. Tap water, which had been filtered through biologically active granular activated carbon, was used as an innoculum for biofilm growth in annular reactors (ARs). Synthetic cocktails of easily biodegradable material in the concentration range of 50–2000 mg C/m 3 were used as substrate for biofilm growth. Influent and effluent aggregate concentrations of biodegradable organic matter (BOM) were calculated by adding the measurable BOM components on a mass carbon basis. The aggregate BOM values were used for calculating the observed Damköhler number and Theile modulus (based on a reaction rate per unit surface area), which were used to determine whether external or internal mass transfer limited BOM removal. For all of the experimental trials, it was shown that neither external nor internal mass transfer limited BOM removal. Because the biofilms in this research are thin and the fact that mass transfer is not limiting, it was assumed that the bulk BOM concentration was approximately equal to the average BOM concentration in the biofilm. A linear model was obtained for the aggregate BOM flux and the product of the effluent BOM concentration and the biofilm density. The slope or the areal biodegradation rate ( k a) for the aggregate BOM was 0.033 m/h, as determined through a linear regression.

Measurement of biomass activity in drinking water biofilters using a respirometric method

A simple respirometric method was developed and applied for the measurement of biomass activity in bench-scale drinking water biofilters. The results obtained with the new method, i.e. biomass respiration potential (BRP), indicated a high sensitivity allowing the quantification of the activity of low amounts of biomass. The analysis of duplicate samples showed a reasonable reproducibility, i.e. average coefficient of variation of 14% ( n=19). The calculation of the ratio between biomass activity and the amount of viable biomass (phospholipid) at different filter depths indicated a substantial increase of this ratio with filter depth. This indicated an increased biomass activity per unit amount of viable biomass deeper in the biofilters, where biofilm thickness is low. The comparison of the filter profiles of biomass activity and dissolved biodegradable organic matter (BOM), expressed as theoretical oxygen demand, showed a high correlation between these profiles. Consequently, BRP results appear to be good indicators of the BOM removal capacity of the filter biomass. Therefore, BRP results can potentially be used in certain cases instead of BOM measurements for the assessment of the BOM removal capacity of drinking water biofilters, operated under different conditions. This is important because of the relative complexity of the measurements of BOM surrogates, e.g. assimilable organic carbon and biodegradable dissolved organic carbon, and BOM components.

10] Biodegradable organic matter measurement and bacterial regrowth in potable water

Publisher Summary This chapter presents the methods available to evaluate biodegradable organic matter concentrations in water, and describes and compares several bioassays commonly used in the drinking water field to assess the bacterial regrowth potential of waters. Because a high biodegradable organic matter (BOM) level is one factor related to bacterial regrowth, BOM removal should be emphasized during water treatment to improve water quality. There is a weak correlation between organic carbon (AOC) and biodegradable dissolved organic carbon (BDOC) concentrations. The BDOC test attempts to identify the entire pool of BOM, including very labile constituents to slowly biodegradable molecules (requiring the successive steps of cell adsorption, exoenzymatic hydrolysis, and cell consumption), whereas the AOC test detects easily assimilable organic compounds. Because both tests emphasize different fractions of biodegradable organic matter, both parameters should be monitored when studying nutrient changes during water treatment and distribution. Because of a long incubation period, using the BDOC suspended bacteria method is not practical at a water utility. A water utility can use either the sand or bioreactor methodology, depending on its testing objectives. Both methods yield to a similar BDOC result. The BDOC sand measurement is recommended for a short study or a limited number of samples.

Non-steady state simulation of BOM removal in drinking water biofilters: applications and full-scale validation

A biofilter model called “BIOFILT” was used to simulate the removal of biodegradable organic matter (BOM) in full-scale biofilters subjected to a wide range of operating conditions. Parameters that were varied included BOM composition, water temperature (3.0–22.5°C), and biomass removal during backwashing (0–100%). Results from biofilter simulations suggest a strong dependence of BOM removal on BOM composition. BOM with a greater diffusivity or with faster degradation kinetics was removed to a greater extent and also contributed to shorter biofilter start-up times. In addition, in simulations involving mixtures of BOM (i.e. readily degradable and slowly degradable components), the presence of readily degradable substrate significantly enhanced the removal of slowly degradable material primarily due to the ability to maintain greater biomass levels in the biofilters. Declines in pseudo-steady state BOM removal were observed as temperature was decreased from 22.5 to 3°C and the magnitude of the change was significantly affected by BOM composition. However, significant removals of BOM are possible at low temperatures (3–6°C). Concerning the impact of backwashing on biofilter performance, BOM removal was not affected by backwash resulting in biomass removals of 60% or less. This suggests that periodic backwashing should not significantly impact biofilter performance as observed biomass removals from full-scale biofilters were negligible. In general, the simulation results were in good qualitative and quantitative agreement with experimental results obtained from full-scale biofilters.

The importance of soluble microbial products (SMPs) in biological drinking water treatment

The formation of soluble microbial products (SMPs) during a drinking water ozone-biofiltration process was estimated using two approaches. First, a model was developed that related the assimilation of biodegradable organic matter (BOM) to the accumulation of biomass on filter media. The model was calibrated with data from a regularly backwashed, pilot scale biofilter that approximated a steady-state plug flow reactor. The second approach was a direct measurement of SMP concentrations, accomplished by applying a synthetic water comprised of known compounds to a bio-acclimated filter. The SMP concentration was estimated by determining the difference between known-compound removal (on a carbon basis) and dissolved organic carbon (DOC) removal. Comparable results were obtained from both approaches. SMPs were found to be important relative to the carbon removal that is typically measured (DOC), indicating that this measurement can significantly underestimate the actual BOM removal (17–33% in this research). The concentration of SMPs was negligible relative to the filter effluent DOC pool.

Biodegradable organic matter removal in biological filters: evaluation of the CHABROL model

The implementation of biological filtration on granular activated carbon under various operating conditions has revealed that biodegradable organic matter (BOM) removal performance is not easily predicted. In this context, the statistical analysis of the differences between experimental data and data calculated by a deterministic model may provide insight into the source of prediction errors. The CHABROL model, developed by Billen et al., (1992), relates BOM consumption to biomass densities in order to predict BOM removal profiles in biological activated carbon filters (BAC) and rapid sand filters. This work presents the results of testing the CHABROL model using a large database from pilot and full-scale filters located in two Canadian cities: Laval and Montreal. This database includes data from two different water sources and three biological filtration configurations (direct filtration, first-stage dual-medium sand-BAC filters and second-stage mono-medium BAC filters). Since nearly half of all experimental data were obtained at very low temperatures (≤1°C), the impact of prolonged acclimation to very cold temperatures was investigated to ensure accurate prediction by the CHABROL model. Experimental results have shown that modifications in the CHABROL model have to be made to account for the acclimation to very cold temperature and to prevent under estimations of the BDOC removals. The results of the model testing show overall satisfactory results in the ability to predict BDOC removals in various types of filters, except for the sampling campaigns completed just prior to backwash. This comparison shows the interest of using a predictive model to predict performance in dynamically operated filters which may be used for design and operation.

BOM removal during biofiltration

Although the biofiltration process may not control the design of a filter bed, results described here can help the engineer better understand the tradeoffs.Pilot‐scale biofiltration experiments were conducted to determine how empty bed contact time (EBCT) and hydraulic loading rate (HLR) affected the removal of biodegradable organic matter (BOM). The removal of BOM formed during ozonation was measured as the reduction (resulting from biodegradation) of dissolved organic carbon in the filter; it was referred to as biodegradable dissolved organic carbon–filter (BDOCfilter). Ten ozone by‐products were measured to understand the composition of BDOCfilter and to assess whether these by‐products might be used as a surrogate for BOM; none sufficed. BOM formed during ozonation limited the removal of BDOC during biofiltration with two exceptions: nonsteady‐state BOM loading conditions and inadequate EBCT. Both of these conditions were limited by biomass formation. HLR had no effect on BDOCfilter even though markedly different biomass profiles were observed.

Benefiting From Biological Growth in Filters

This article discusses biological filtration, or biofiltration, a process that uses innocuous microorganisms for the breakdown and removal of biodegradable organic matter (BOM). Topics covered include: treatment plant design; biofilm problems; process effectiveness; the key to successful biofiltration processes; monitoring and evaluation; occurrence in various media; and, historical use of biofiltration.

Backwashing first‐stage sand–BAC filters

Does it increase removal of biodegradable organic matter and ammonia?The effect of filter backwash on the efficiency of first‐stage sand–biological activated carbon (BAC) filters was evaluated by comparing, in first‐stage sand–BAC filters, concentrations of ammonia, biodegradable dissolved organic carbon, aldehydes, and oxalate. These concentrations were measured before and after filter backwash. Filter position (first‐stage sand–BAC filters versus second‐stage BAC filters) was also studied to understand how flocs and particle accumulation influenced the efficiency of the first‐stage sand–BAC filter. A first‐stage sand–anthracite filter operated under similar hydraulic conditions and effluent turbidity acted as a reference. Filter backwash improved the efficiency of sand–BAC filters, especially in cold water sources. However, both filters produced similar water quality. First‐stage sand–anthracite filters did not adequately remove biodegradable organic matter and ammonia.

Deposition and retention of bacteria in backwashed filters

Biomass accumulation in laboratory‐scale filters is not impaired by backwash with water alone.Experiments tracked the deposition of two model bacteria—Pseudomonas aeruginosa and Klebsiella pneumoniae—onto clean filter media (i.e., glass beads and filter sand) and the subsequent removal of the bacteria by backwashing. The ability of bacteria to accumulate and be retained in a frequently backwashed filter is critical for effective removal of biodegradable organic matter in a process termed biofiltration. Column filtration experiments showed that the bacteria, especially P. aeruginosa, readily attached to the filter media during filtration, despite unfavorable chemical conditions. Water backwash was not effective at removing bacteria from the filter media, with only 20–40 percent removal during 10‐min backwash cycles at hydraulic loading rates ranging from 23 to 53 m/h (9.3 to 22 gpm/sq ft) and bed expansions ranging from 15 to 50 percent. Incomplete removal of biomass during backwashing was beneficial for removal of biodegradable total organic carbon, typically allowing a backwashed biofilter to maintain treatment at levels similar to the period immediately preceding the backwash.