Performance Of Biological Filters For Drinking Water Treatment And Their Use For High Pressure Membrane Biofouling Control

Biofiltration is a promising green drinking water treatment technology that can reduce the concentration of biodegradable organic matter (BOM) in water. Direct biofiltration or biofiltration without pretreatment (BFwp) limits the use of chemicals such as coagulants or ozone commonly employed with conventional biofiltration, making BFWP a more environmental friendly pre-treatment. BFWP was proven to be an efficient pretreatment to reduce fouling of low pressure membranes, and can also improve the biological stability of the final treated drinking water to limit bacterial regrowth in the distribution system. One major operational problem for high pressure membranes (i.e. nanofiltration and reverse osmosis membranes) is membrane biofouling due to biofilm growth inside the feed channel of the membrane module, resulting in higher energy requirements and more frequent membrane cleaning. BFWP can potentially be applied to reduce biofouling of nanofiltration membranes, which can reduce the energy requirements of high pressure membranes. Three pilot-scale parallel biologically active filters with different empty bed contact times, and bench-scale nanofiltration membrane fouling simulators, were designed and constructed in this study. A challenging surface water source (the Grand River in Kitchener, ON) was used as source water for the investigation. Initial work assessed the effect of biofiltration on the treated water quality and how the biofilter performance is affected by changes in water temperature. A protocol was developed to better characterize the biofilter attached biomass and extracellular polymeric substances (EPS), in order to understand their possible relationship to biofilter performance. Flow cytometry was applied to measure both planktonic cell concentrations in water and also to perform assimilable organic carbon (AOC) analysis using a natural microbial inoculum. BFWP was found to be an efficient pre-treatment for the removal of large molecular weight biopolymers and AOC over a wide range of water temperatures. Lower water temperatures had a significant impact on biopolymer removal, unlike AOC which was efficiently removed at lower water temperatures, and this proved the robustness of such a pre-treatment technology. Other fractions of the natural organic matter (NOM) such as humic substances, buildings blocks and low molecular weight organics were removed to a lower extent than biopolymers or AOC. Empty bed contact time (EBCT) as a design parameter had a limited effect on the biofilter performance. Most of the observed removal for BOM and total cell count happened at the shortest EBCT of 8 minutes, and increasing the EBCT up to 24 minutes had a significant but less proportional impact on biofilter performance. Regarding biofilter attached biomass, no direct linkage was found between biofilter performance and attached biofilter biomass characteristics using any of the commonly used analytical methods such as adenosine triphosphate (ATP) or biofilm cell count, however, cellular ATP content was found to be indicative of biofilm activity. Biofilm EPS composition was not related to biofilter performance but it was largely affected by the water temperature. Through community level physiological profiling (CLPP) analysis it was evident that the microbial community was changing due to a drop in water temperature, however, this was a minor effect and it is likely that the overall drop in biomass activity was the main reason behind the drop in biofilter performance. Finally, BFWP was tested as a potential pre-treatment technology to control high pressure membrane biofouling, which is a major operational problem. BFWP was able to reduce the amount of available nutrients measured as AOC, reduce the presence of conditioning molecules such as large molecular weight biopolymers, and modify the microbial community of the feed water. A 16 minute EBCT biofilter was able to extend the lifetime of nanofiltration membranes by more than 200% compared to the river water without biofiltration, both at low and high water temperature conditions. The 16 minute EBCT biofilter performance was also comparable to that of a full scale conventional biofilter with prior coagulation, sedimentation and ozonation. The biofiltration pre-treatment efficiently affected the amount of biomass present in the biofouling layer and affected the biofilm microbial community as determined using CLPP analysis. The findings of this study provide the basis upon which further and larger scale testing of the BFWP as a pre-treatment for membrane applications can be done. A sound technology could include a hybrid membrane system with a high pressure membrane proceeded with a low pressure membrane. BFWP can then be used at the start of the treatment train to limit both low pressure membrane fouling at the same time limit the biofouling of the pressure membrane. This treatment train can provide a high water quality with limited footprint compared to conventional treatment trains and long service time. Monitoring of the treatment unit performance can be efficiently done using some of the proposed analytical methods presented in the study, such as AOC monitoring and flow cytometry to study microbiological water quality and biofilter biomass. Fluorescence spectroscopy and size exclusion chromatography can also be used to monitor large molecular weight biopolymers, which are responsible for several operational problems in water treatment in general and specifically for membrane applications.

Natural organic matter (NOM) is a concern in many surface waters and must be removed by water treatment processes for cost-effective production of safe and aesthetically pleasing drinking water. Biological filtration is an appealing NOM removal method due to its simplicity and low maintenance requirements. Biofiltration is not traditionally used in water treatment headworks, however biofiltration without pretreatment (BFwp) breaks with common practice to function as both particle and biodegradable NOM removal as a 1st stage process. BFwp makes use of indigenous microbial populations embedded in a biofilm matrix to remove biodegradable organic matter (BOM) from raw source water. This configuration is a viable pretreatment strategy for both low and high pressure membrane filtration due to its ability to remove both particulate and soluble BOM, thereby mitigating biofouling on the membrane surface. Biofouling has been described as the "Achille's heel" of membrane filtration (Flemming et al., 1997) due to its effects of increased operational cost and shortened membrane life-span. Therefore, a targeted effort is needed to understand how biofilter ecology affects performance both in the biofilter and downstream in membrane filtration units. Two parallel pilot scale BFwp units with dual-media were used in the current study for a seasonal characterisation of biofilter microbial dynamics and performance. Refurbishment of the biofilter pilot plant was performed by Dr. Ahmed Elhadidy and Brad Wilson, former students of the NSERC chair in water treatment. The current seasonal characterization spanned 14 months and made use of both new sample material as well as archived samples from Dr. Elhadidy. Biofilter media biomass was assessed using both adenosine tri-phosphate (ATP) and flow cytometric methods. Total protein, carbohydrate and free DNA of the media biofilm extracellular polymeric substances (EPS) were determined. Polymerase Chain Reaction - Denaturing Gradient Gel Electrophoresis (PCR-DGGE) was used to create microbial community fingerprint profiles of the biofilter feed and media. It was found that source water quality played a significant role in shaping BFwp microbial communities. Multivariate analysis of the PCR-DGGE fingerprints showed a media biofilm community shift occurred in response to high ammonia, high low molecular weight acids (LMW-acids) concentrations in the raw feed during January-February 2015. This low temperature, high ammonia and LMW-acids induced shift was accompanied by a rise in media biomass and EPS. Lower DOC and biopolymer removals were observed during the January-February 2015 community shift, however this was attributed largely to the effects which lower feed temperatures have on microbial biodegradation kinetics. No differences were found in community structures between media types, depths, or biofilter columns, however source water exhibited lower diversities and markedly different community structure than those of media biofilms. It was determined that media diversity and richness were high and did not exhibit seasonal fluctuations. As such these parameters could not be reliably related to biofilter DOC and biopolymer removal performance. In his investigation of biofiltration as a pretreatment for nanofiltration (NF), Dr. Elhadidy archived samples for molecular analysis that were used in the current study. PCR-DGGE was performed on extracted DNA from source water, media, and fouled membrane samples for bacteria, archaea, and fungi. Archaea were present in all samples, however their abundance was roughly 1000 fold less than bacteria, which made it difficult to assess their significance in the biofiltration and NF processes. Fungi were only screened for in one media and one source water sample during method development; both samples were positive. Archaeal community organisation was similar to that of bacteria during the autumn BF-NF experiment, however no community organisation was discernible during the winter experiment. Bacterial community structures from the autumn experiment showed that fouled NF membranes fed raw water clustered together with biofilter media, indicating feed water rather than substrate material influences bacterial community organisation. Comparatively, NF membranes fed with biofilter effluent produced a cluster of drastically dissimilar bacterial communities, which corresponded with improved flux and reduced biofoulant biomass. The microbial communities of biofiltration exhibited dynamic responses to feed water quality in both the seasonal and the nanofiltration studies. Biomass and EPS were highly correlated and their levels changed in response to community shifts, which in the seasonal and nanofiltration studies, were precipitated by changes in feed ammonia and BOM.

The goal of drinking water treatment is to produce and deliver safe water to the consumers. To achieve these objectives water treatment plants are designed based on the concept of the multibarrier approach which combines several drinking water treatment processes in order to increase the reliability of the system. The presence of pharmaceutically active compounds (PhACs), personal care products (PCPs) and endocrine disrupting compounds (EDCs) in drinking water sources is becoming a concern, because of chronic and indirect human exposure to contaminant mixtures at sub-therapeutic levels via drinking water consumption. Membrane filtration can be an efficient treatment process to remove microorganisms and/or trace organic contaminants from drinking water sources. However, membranes are confronted by a major limitation: membrane fouling. Fouled membranes suffer from a loss in performance either leading to a reduction in flux or a higher pressure requirement. Generally, membrane fouling increases the need for membrane maintenance measures such as backwashing and chemical cleaning which has a negative impact on the operating costs and membrane life time. Severe membrane fouling may even impact permeate quality and/or compromise membrane integrity. The aim of this study was to establish if biofiltration pretreatment without prior coagulation would be able to control membrane fouling in natural waters. The second objective investigated the removal of trace organic contaminants by individual treatment processes (i.e. biofiltration and membrane filtration). Parallel to this work, the presence and concentration of selected trace organic contaminants in Grand River (Ontario, Canada) were determined. The trace organic contaminants investigated included atrazine, carbamazepine, DEET, ibuprofen, naproxen, and nonylphenol.

This text provides an overview of the developments since 1986 in the control of biofouling and reduction of the costs incurred by biofouling organisms. Topics covered include: microfouling; macrofouling; and the performance of antifouling coatings.

Membrane filtration is growing in popularity as a viable technology for drinking water treatment to meet high demand and regulatory requirements. While many improvements have been made to the technology in the past decade, fouling continues to be one of the major operational challenges associated with membranes as it increases operating costs and reduces membrane life. Fouling control typically requires some form of pre-treatment. Biofiltration is a “green” technique that can minimize chemical usage and waste during water treatment and is a relatively new application as a pre-treatment for membranes. Proteins and polysaccharides (biopolymers) have been found to contribute most to fouling of low pressure polymeric membranes. Biofiltration has recently been demonstrated as an effective pre-treatment method for reducing biopolymer-associated fouling of this type of membrane (Hallé et al., 2009). Given that the concentration and composition of organic matter in water is variable, there is an opportunity to explore the applicability of this robust technology for different water types. The primary goals of this research were to assess the effectiveness of direct biofiltration in minimizing ultrafiltration polymeric (PVDF) membrane fouling and at the same time evaluate the biofilter development, biofilter performance based on organics removal potential, and the effect of phosphorus addition (as a nutrient) to the biofilter influent. A pilot-scale treatment train was constructed at the Technology Demonstration Facility at the Walkerton Clean Water Centre. It included two parallel dual media (sand/anthracite) biological filters (preceded by roughing filters), followed by an ultrafiltration membrane unit. Experiments were conducted using water from the Saugeen River (Ontario, Canada) whose primary form of carbon is humic material. The biofilters were allowed to acclimate and biofilter performance and organics removal were tested over a fourteen month period, the last four months of which were dedicated to phosphorus enhancement experiments. The membrane fouling experiments started seven months following the start-up of the biofilters, after confirmation of steady-state operation. Biofilter water samples were analyzed for natural organic matter constituents along with other water quality parameters, and biomass quantity and activity in the media were measured. Biomass activity in the biofilter media and biopolymer removal through the biofilter indicated a rapid acclimation period, and also demonstrated similar performance of the parallel biofilters during start-up and steady-state operation. The biofilters achieved 21% removal of the biopolymers on average following acclimation, while reduction of the humic fractions was not observed. A linear relationship between biopolymer removal and its concentration in the river water was observed (first-order process). Membrane fouling experiments were conducted using both untreated and biofiltered river water. The fouling rates were computed by monitoring changes in transmembrane pressure over time. Analysis of the samples with liquid chromatography-organic carbon detection confirmed the significant contribution of biopolymers to irreversible and reversible membrane fouling rates even when only present at low concentrations. During the phosphorus enhancement phase, two different phosphorus doses were fed into the influent of one of the parallel biofilters in order to achieve a target C:N:P ratio of roughly 100:10:1. Although initially (first month of the dosing period) an increase in the removal of dissolved organic carbon and ultraviolet-absorbance was observed in the phosphorus-enhanced biofilter, this was not sustained. Phosphorus addition did not affect biopolymer removal or biomass quantity and activity in the biofilter, and the membrane fouling experiments during this period did not show any significant effect of phosphorus addition.

The use of ultrafiltration membrane technology for drinking water treatment has seen a marked increase in the past few decades, however, membrane fouling remains the top technological hurdle in the way of its widespread use. Multiple membrane pretreatment methods exist to alleviate this issue, however, they can be complicated and involve the addition of chemicals to the system. A novel method, known as biofiltration without pretreatment, is a green alternative to conventional membrane pretreatment, and has been shown effective at both the laboratory and bench scale in proof of concept studies. It is unknown if the conventional biofiltration operational experience, applies to biofiltration without pretreatment especially as it relates to filter backwashing. To this end, the goal of this study was to investigate the performance of biofiltration without pretreatment as a membrane pretreatment under varying water quality conditions, as well as to test the effect of various backwashing parameter settings on the system performance. To perform this study, a pilot plant was constructed at the Mannheim water treatment plant in Kitchener Ontario. This plant consisted of multiple identical biofilter columns running in parallel. For this study, dual identical biofilters run in parallel were used, with one being a control and run under constant backwashing conditions, while the other, an experimental filter, was run over a range of backwashing conditions according to a statistical experiment design. The dual media filters (anthracite over sand) used in this study were run with a 7 minute empty bed contact time. This study was divided into two parts. In the first part, focus was placed on the performance of the biofilters and in the second part the combined process, that is the use of biofilters without pretreatment as a membrane fouling reduction pretreatment, was investigated. In both cases, the effect of changing inlet water quality parameters, as well as the effect of backwashing parameters (collapse pulsing time, wash time, wash expansion and membrane run delay) was investigated. Performance of both sections of the plant was monitored through a combination of online and laboratory measured parameters. Biofilter turbidity, temperature, headloss, as well as membrane temperature and transmembrane pressure were monitored online. In the laboratory, liquid chromatography with organic carbon detection was used to measure the concentrations of various water constituents. Fluorescence emission and excitation matrices were also used for this purpose. In addition, dissolved organic carbon, and ultraviolet light absorption were also measured. The consumption of dissolved oxygen by biofilms attached to biofilter media was quantified as a means to determine biological activity within the biofilter. In terms of biofilter performance, the backwashing factors studied were found to have no effect on the biological activity, either through the removal of nutrients, or by the amount of biomass on the biofilter media. However, these factors were found to influence turbidity removal and headloss accumulation by the biofilters as well as the removal of suspected membrane foulants, namely biopolymers and protein-like material In terms of membrane performance, the irreversible fouling rate was found to be correlated to the amount of biopolymers applied to the membranes and reversible fouling was found to not be correlated to any of the parameters studied. The amount of turbidity applied to the membranes was shown to a play a complex, role in this fouling as well. Backwashing was also shown to have an effect on irreversible fouling, suggesting that the backwashing regime may be optimized for the reduction of irreversible fouling. Although the backwashing procedure was found to have an effect on both the reduction of irreversible membrane fouling and the headloss buildup (hence biofilter run time), these two parameters were found to be affected in opposite , meaning that one may be optimized at the expense of the other. Therefore process optimization must be undertaken with specific goals in mind. It was found however, that the filter run time of the biofilters may be extended by optimizing the biofilter backwashing procedure. The results of this study provide a frame work for which to further study the influence of backwashing on biofiltration without pretreatment used as a membrane pretreatment by pointing to the backwashing parameters which have the greatest effect on performance. Moreover, the results of this study may be used as a starting point for more in depth optimization exercises.

Ceramic membranes have been widely and successfully used in the food and beverage processing industry. Despite their success, ceramic membranes are not commonly employed in drinking water treatment due to their high initial capital cost. Polymeric membranes, on the other hand, have gained widespread use in drinking water treatment in the last few decades due to their ability to meet stringent water quality regulations. Ceramic membranes have a number of advantages over polymeric membranes, which include high chemical and thermal stability, higher fluxes and longer operational life. Advances in membrane technology in recent years coupled with innovative design have made the life cycle cost of implementing ceramic membranes competitive with that of polymeric membranes. This has resulted in a number of drinking water treatment plant installing ceramic membranes as part of the treatment process, especially in Japan. The biggest challenge facing membrane filtration (polymeric or ceramic) is fouling. To control fouling, coagulation prior to ceramic membrane filtration is often implemented and has been shown to be effective in controlling both hydraulically reversible and irreversible fouling. Direct biofiltration without pretreatment (BFWP) (coined by Huck et al., 2015) has been shown to be another effective “green” pretreatment to control fouling in polymeric membranes. High molecular weight natural organic matter (NOM) such as biopolymers have been found to be directly related to the hydraulically reversible fouling and to play a key role in hydraulically irreversible fouling of polymeric membranes and biofiltration is able to reduce the concentration of this NOM fraction. Given the effectiveness of BFWP in controlling fouling in polymeric membranes, there is an opportunity to investigate its applicability to ceramic membranes. Therefore, the goals of this study were to investigate the efficacy of BFWP as a pretreatment to control fouling in ceramic membranes and characterize the fouling of the membranes over time. The effects of Empty Bed Contact Time (EBCT) of the biofilters, membrane materials and pore sizes (Microfiltration (MF) vs. Ultrafiltration (UF)) on the fouling rates were also investigated in the study.

Biofiltration is capable of reducing DBP precursors and other contaminants in drinking water treatment. However, conventional polishing biofilters are prone to biofouling due to low nutrient levels. A roughing biofilter earlier in the process was evaluated as an alternative. Lab-scale experiments used a crystal violet (CV) assay for quantifying biofilm establishment on two roughing biofilter media: a porous ceramic ring and a honeycomb-style trickling filter media. Limitations with the CV assay for this application were identified. Pilot-scale roughing biofilters were installed at a drinking water plant for 70-days and operated to maximize biofilter performance. Biological activity was confirmed as CV absorbance increased from 0.085 to 0.400 AU. However, correlations of biological activity with water quality improvements were not possible, prompting several suggestions for future research including increasing the empty bed contact time (filter depth), starting up the filters in a laboratory setting, and monitoring changes in the organic carbon composition.

The revised Third Edition of The Prokaryotes, acclaimed as a classic reference in the field, offers new and updated articles by experts from around the world on taxa of relevance to medicine, ecology and industry. Entries combine phylogenetic and systematic data with insights into genetics, physiology and application. Existing entries have been revised to incorporate rapid progress and technological innovation. The new edition improves on the lucid presentation, logical layout and abundance of illustrations that readers rely on, adding color illustration throughout. Expanded to seven volumes in its print form, the new edition adds a new, searchable online version.

The book covers the subject of membrane bioreactors (MBR) for wastewater treatment, dealing with municipal as well as industrial wastewaters. The book details the 3 types of MBR available and discusses the science behind the technology, their design features, operation, applications, advantages, limitations, performance, current research activities and cost. As the demand for wastewater treatment, recycling and re-use technologies increases, it is envisaged that the membrane separation bioreactor will corner the market. Contents Membrane Fundamentals Biological Fundamentals Biomass Separation Membrane Bioreactors Membrane Aeration and Extractive Bioreactors Commercial Membrane Bioreactor Systems Membrane Bioreactor Applications Case Studies