Carbon-based Nutrient Enhancement to Improve Biofiltration Performance for Drinking Water Treatment PDF Download
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Author: Yu Zhao
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Biofiltration is a popular drinking water treatment strategy due to its ability to biodegrade organic and inorganic substances. However, water treatment plants have faced the problem of low biomass concentration (
Author: Yu Zhao
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Biofiltration is a popular drinking water treatment strategy due to its ability to biodegrade organic and inorganic substances. However, water treatment plants have faced the problem of low biomass concentration (
Author: Yaron Zinger
Publisher:
ISBN:
Category :
Languages : en
Pages : 646
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Stormwater runoff is a leading cause of water quality degradation in many urban waterways and receiving waters. In addition, rapid urbanisation and climate change effects are elevating the pressure on the use and resourcing of freshwater supplies. Stormwater harvesting has the potential to harness this conventional nuisance into a reliable potable resource if a suitable treatment can be achieved. Excess nutrients and nitrogen in particular are carried by stormwater, potentially leading to eutrophication. Biofilters, also known as bioretention systems, have shown the potential to remove nutrients from stormwater, thus protecting receiving waters as well as providing significant landscape amenity and urban microclimate benefits. In biofilters, nitrogen compounds can be transformed and ultimately converted into nitrogen gas by coupled nitrification and denitrification, providing the sustainable removal of nitrogen. Current biofilter designs, however, have not yet been optimised for efficient nitrogen removal. Additionally, current biofilter systems are considered a "black box" in terms of nitrogen species transformation, with little known about the variations in their performance, particularly in relation to the harsh wetting and drying environment to which they are subjected. The present thesis has examined the processes involved in nitrogen removal (and to a lesser degree phosphorus removal), focusing particularly on nitrate removal dynamics and its optimisation in biofilters. The first step was a large scale base-line study that was designed to quantify the removal performance of conventional biofilter designs. The findings targeted the need to enhance NOx removal, by optimising components of the design, leading to new configurations. The novel design was tested for typically harsh operational conditions, such as prolonged drying periods and system recovery. In order to meet water quality guidelines, laboratory results were validated in the field through a full-scale biofiltration system, which also tested the effectiveness of the optimised designs in removing a range of pollutants from urban runoff. In the first stage of the thesis, a large scale study of 140 columns tested eight different biofilter design and operational factors. Overall, this study revealed that whilst biofilters could readily remove high levels of sediment (averaging 98% removal), phosphorus (85%) and heavy metals (greater than 90% removal for most metals), nitrogen removal was often poor. NOx in particular, leaches from the biofilters after dry weather spells, In addition, NOx removal was strongly dependent on the type of vegetation. It was concluded, therefore, that systems should be carefully designed, paying particular attention to the specification of the soil media and selection of the plants to assure the required nutrient removal. For the conditions testing, a biofilter system of 2% of its impervious area with a minimum filter media depth of 5OO mm was found to be satisfactory. Finally, the biofilter columns demonstrated the facility to achieve and maintain removal capacity even under high concentration inflows. The next study investigated nitrogen transformations and improved removal of NOx through denitrification. In order to achieve this, 18 advanced biofilter columns were constructed and incorporated into different levels of a saturated zone (SAZ), supplemented with a carbon source. Sampling ports enabled measurement of nitrogen transformations throughout the filter depth profile. The SAZ design columns demonstrated removal of NO x, ammonia, organic nitrogen and mean TN removal of up to 74%. The columns, which included carbon substrate in their SAZ, demonstrated more than 99% success in removing NOx, statistically more than the control columns that did not use carbon which removed less than 50% NOx. Moreover, the depth concentration profile exhibited the highest NOx reduction along the SAZ biofilter section, suggesting that the addition of organic carbon as an electron donor in the saturated zone is beneficial to the rate of denitrification; a saturated zone depth of 450 mm was found to be effective. Moreover, a subsequent study investigated the efficiency of the SAZ design during prolonged drying and subsequent rewetting periods, and found that having a saturated zone (SAZ) is critical for efficient nitrogen removal in dry periods of more than two weeks. Without the SAZ, the biofilters behave as a source rather than a sink for nitrogen and NOx in particular. Furthermore, the SAZ design showed much faster recovery of N removal upon rewetting; the SAZ design biofilters were able to recover nitrate removal after only one rewetting event. Without the SAZ, the recovery time may be longer than the antecedent dry period itself, meaning that net leaching will occur during several storm events before net removal is re-established. Finally, the laboratory biofilter results were validated in the field by introducing a large scale biofilter pilot in Israel adopting a dual mode system; 1. A stormwater harvesting operational mode (during the rainy season) and 2. An aquifer recovery mode (during the dry season) for treatment of highly pollutant groundwater with nitrate. The removal performance for sediments and nutrients in the field was similar if not better than predicted in the laboratory; TSS concentrations were reduced by 99.4% (lab; 98.1%), TP by 94% (lab; 70%), and TN by 65% (lab; 64%, SAZ=6OO mm). The field study results confirmed a high removal performance not only for nutrients, but also for heavy metals, pathogenic indicators, and TOC. The biofilter was found to treat the stormwater and met water quality standards for irrigation and stream health, achieving even the most stringent local drinking water guidelines (not for pathogens contamination). For example, it demonstrated high reductions of E-coli and Faecal Coliforms in the range of 2- 3 log reductions, and below the maximal permitted values for the majority of metals and measured nutrients. This does not mean that the outflows are directly drinkable without additional filtration and disinfection, but that the data demonstrates the potential of stormwater to eventually become the first stage in a potable water source or alternatively this can be safely recharged into the aquifer. Aquifer recovery application results show potential for nitrate removal in the remediation of contaminated groundwater, albeit at low flow rates and under batch flow regimes. In these conditions, the biofilter managed to remove up to 73% of the nitrate concentration within the contaminated aquifer and met the drinking water guideline for nitrate. The present research contributed many recommendations for the design of biofilters and operational recommendations that are listed in FAWB adoption guidelines (2009)1. One of the key design recommendations arising from the present research, however, is that, where possible, biofilters should incorporate SAZ and a supplementary carbon source within the filter media, to enhance their robustness and nitrogen removal. The presence of the SAZ design can buffer some inefficiency ineffective traits of conventional biofilters, while at the same time sustaining vegetation growth during dry periods. In fact, retrofitting the SAZ into 'simple' biofilters is recommended if the existing biofilter has inadequate N removal and if N discharges poses a potential threat to the receiving environment. A number of knowledge gaps and research challenges were identified from the current research. For example, the need to enhance the removal of organic nitrogen from stormwater, since it was observed as the primary N form in the biofilter effluent (86% of total N). This study also suggests that biofilters when deployed in practice as a decentralised system may serve several purposes simultaneously. This would require further research and testing to allow the optimisation of stormwater harvesting and the aquifer recovery of nitrate through a constant flow regime. This research has provided comprehensive insights and practical design recommendations to improve biofilter performances, while allowing safer and more versatile use. The practical applications of this research are currently being adopted in Australia, Israel and in other countries.
Author: Ishita Rahman
Publisher:
ISBN:
Category :
Languages : en
Pages : 140
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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.
Author: Daisy B. Badilla
Publisher: GRIN Verlag
ISBN: 3963555300
Category : Nature
Languages : en
Pages : 228
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Doctoral Thesis / Dissertation from the year 2011 in the subject Environmental Sciences, grade: Passed, University of the Philippines, course: Doctor of Philosophy in Environmental Engineering, language: English, abstract: In this study, the influence of water content on biofiltration performance was investigated. A biofilter reactor with water content control through changes in matric potential in a suction cell was used to treat toluene-contaminated air with soil as the filter bed medium. Results suggest the soil water content should be controlled at about 96% (dry weight) or a matric potential of -10 cm H2O. The maximum elimination capacity in this study appears to be a restricted to a narrow water content and this narrow range impacts on the operation of full-scale biofilters as traditional techniques for water content control would make maintaining this range difficult. Biofiltration, which is also sometimes referred to as bio-oxidation, is a method of air pollution control where contaminants in a gas stream are metabolized by microorganisms and converted to water, carbon dioxide and biomass. Biofiltration involves biological, chemical, and physical processes. It is often preferred over other air pollution control technologies since it does not produce secondary pollutants and does not involve expensive maintenance and operating costs. However, one of its disadvantages is the difficulty in controlling water content. A water retention curve of the soil was generated by plotting water content versus matric potential with data obtained using the suction cell. Two additional factors, concentration and nutrient addition, were investigated using two other soil biofilters. Improved biofiltration performance was observed at higher toluene concentrations. High toluene concentrations may be advisable during start-up as it converts microorganisms that do not thrive on toluene into nutrients for desired degraders inducing growth and improved performance but would have to be controlled to avoid excessive growth. In the membrane biofilter, the large pores in the biofilm contributed to a possible enhancement of pollutant and oxygen mass transfer. Nutrient addition improved the volumetric removal rate of toluene which implies that available nutrient has been limited. Nitrogen was identified as limiting the biomass growth. The production of carbon dioxide confirmed effective biodegradation of toluene in the soil biofilter. This study contributes to existing knowledge relevant conclusions and recommendations that may guide biofiltration operation, broaden concepts, or direct future studies and it considers treatment of indoor air pollution as a particular area of application.
Author: Vivek Aditya Nemani
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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This research examined operational efficiency and performance enhancement of passive and engineered biofiltration. Pilot studies were carried out to evaluate the impact of backwash frequency, empty bed contact time, and nutrient enhancement on biofiltration systems treating different source waters (Lake Ontario and Lake Simcoe). Performance was evaluated in terms of organic carbon, ultrafiltration foulant (biopolymer), and disinfection-by product precursor removal. Increasing empty bed contact time from 4 to 8 min enhanced organic carbon degradation, while there was no statistically significant impact on biopolymer removal. Extending filter run time beyond 15 days had a detrimental effect on turbidity; however, no significant impact was observed in the monitored parameters when biofilters were backwashed every 10 days, which would result in economic benefits. Phosphorus addition (0.3 mg/L) improved organic carbon and disinfection by-product precursor removal, while nitrogen addition (0.8 mg/L) had no significant impact in spite of being consumed entirely through the biofilter.
Author: Amina K. Stoddart
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Natural organic matter (NOM) is a complex mixture of organic material ubiquitous in natural waters. NOM can affect nearly all aspects of drinking water treatment. It can exert a demand on treatment chemicals, promote regrowth in distribution systems and can form genotoxic and/or carcinogenic disinfection by-products (DBPs) when exposed to disinfectant. Biofiltration is one treatment strategy that has potential to provide additional removal of NOM following coagulation. In biofiltration, bacteria indigenous to the source water form biofilms on filter media and use organic material as an energy source. This type of biological treatment within a filter has advantages over filtration with relatively biologically inert granular media because of its potential to provide additional NOM removal through biodegradation. This thesis investigated conversion of full-scale anthracite-sand drinking water filters to biofilters through the removal of prechlorination. Results showed that filters operated in direct filtration mode could be converted in this way to reduce DBP formation in the plant effluent and distribution system without compromising water quality or filter performance. Biomass monitoring using adenosine triphosphate (ATP) showed that filter media biomass increased as a result of conversion. Further interpretation of the biomass data with a growth model demonstrated that consistency in biomass sampling within the context of the operational state of the filter or following significant process changes was critical information for long-term performance assessment. A concurrent pilot-scale investigation tested nutrient, oxidant and filter media enhancement strategies with the goal of improving NOM removal and further reducing DBP formation. Results showed that nutrient and oxidant addition could increase the filter biomass and alter the microbial community, but would not improve NOM removal or further reduce DBP formation potential. Ultimately, despite reductions in DBP formation and increases in biofilter biomass, NOM removal across the biofilters remained unchanged with conversion and enhancements, posing a challenge for process monitoring. A novel method to measure oxygen demand was optimized for use in a drinking water matrix and used to evaluate NOM removal and transformation in the biofilters.
Author: Rolf Gimbel
Publisher: IWA Publishing
ISBN: 1843391201
Category : Science
Languages : en
Pages : 580
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Book Description
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.
Author: Balsher Singh Sidhu
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Zaid K. Chowdhury
Publisher: American Water Works Association
ISBN: 1583219072
Category : Technology & Engineering
Languages : en
Pages : 353
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Book Description
"Many books have been written about granular activated carbon. Some focus on the theory of performance and removal mechanisms while others focus on design features. This book focuses on solutions. It describes the challenges facing water providers to provide safe water that is acceptable to their customers, utility experiences using activated carbon, activated carbon applications, and design and procurement approaches. The appendices include detailed case studies and a life-cycle assessment demonstrating favorable sustainability considerations for activated carbon when compared to other treatment technologies. Never before has all of this information been together in one location. The what, why, and how of activated carbon are connected in this book and demonstrate why this treatment technology has maintained its status as an integral treatment technology in the quest for pure water over millennia"--
Author: Ahmed Mohamed Elsayed ElHadidy
Publisher:
ISBN:
Category : Biofilms
Languages : en
Pages : 235
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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.
