DWES - Latest Articles

Method development for arsenic analysis by modification in spectrophotometric technique

Wed, 04 Jan 2012 00:00:00 +0100

Method development for arsenic analysis by modification in spectrophotometric technique

Drinking Water Engineering and Science, 5, 1-8, 2012

Author(s): M. A. Tahir, H. Rasheed, and A. Malana

Arsenic is a non-metallic constituent, present naturally in groundwater due to some minerals and rocks. Arsenic is not geologically uncommon and occurs in natural water as arsenate and arsenite. Additionally, arsenic may occur from industrial discharges or insecticide application. World Health Organization (WHO) and Pakistan Standard Quality Control Authority have recommended a permissible limit of 10 ppb for arsenic in drinking water. Arsenic at lower concentrations can be determined in water by using high tech instruments like the Atomic Absorption Spectrometer (hydride generation). Because arsenic concentration at low limits of 1 ppb can not be determined easily with simple spectrophotometric technique, the spectrophotometric technique using silver diethyldithiocarbamate was modified to achieve better results, up to the extent of 1 ppb arsenic concentration.

Effect of fouling on removal of trace organic compounds by nanofiltration

Wed, 21 Dec 2011 00:00:00 +0100

Effect of fouling on removal of trace organic compounds by nanofiltration

Drinking Water Engineering and Science, 4, 71-82, 2011

Author(s): S. Hajibabania, A. Verliefde, J. E. Drewes, L. D. Nghiem, J. McDonald, S. Khan, and P. Le-Clech

The fate of chemical of concern is not yet fully understood during treatment of impaired waters. The aim of this paper is to assess the impact of different organic-based fouling layers on the removal of a large range of trace organics. Both model and real water samples (mixed with trace organic contaminants at environmental concentration of 2 μg l⁻¹) were used to simulate fouling in nanofiltration under controlled environment. The new and fouled membranes were systematically characterised for surface charge, hydrophobicity and roughness. It was observed that fouling generally reduced the membrane surface charge; however, the alterations of the membrane hydrophobicity and surface roughness were dependent on the foulants composition. The rejection of charged trace organics was observed to be improved due to the increased electrostatic repulsion by fouled membranes and the adsorption of the trace organic chemicals onto organic matters. On the other hand, the removal of nonionic compounds decreased when fouling occurred, due to the presence of cake enhanced concentration polarization. The fouling layer structure was found to play an important role in the rejection of the trace organic compounds.

Application of optical tomography in the study of discolouration in drinking water distribution systems

Wed, 07 Dec 2011 00:00:00 +0100

Application of optical tomography in the study of discolouration in drinking water distribution systems

Drinking Water Engineering and Science, 4, 61-69, 2011

Author(s): P. van Thienen, R. Floris, and S. Meijering

Theories describing the turbulent deposition of particles from aerosols have recently been applied to drinking water distribution. In order to allow the study of these processes in a quantitative way and internally observe a cloud of suspended particles in a pipe, we have developed an optical tomography technique and measuring device using low cost electronic components specifically for this application. The mathematical methodology and the electronic device are described in this paper, and tests of both the mathematical approach and the actual device are presented. We conclude that the mathematical framework presented is suitable and that the technical implementation works in a test setting. The described methodology may provide a valuable tool for the study of processes related to drinking water discolouration in the lab.

Status of organochlorine pesticides in the drinking water well-field located in the Delhi region of the flood plains of river Yamuna

Fri, 11 Nov 2011 00:00:00 +0100

Status of organochlorine pesticides in the drinking water well-field located in the Delhi region of the flood plains of river Yamuna

Drinking Water Engineering and Science, 4, 51-60, 2011

Author(s): P. K. Mutiyar, A. K. Mittal, and A. Pekdeger

This study presents the occurrence of pesticides in a well-field located in Yamuna flood plain of Delhi region. Ground water sampling campaigns were carried out during pre-monsoon and post-monsoon periods covering 21 borewells and 5 Ranney wells. Major 17 organochlorine pesticides (OCP's) along with other water quality parameters were monitored during this period. Pesticide concentrations were determined using GC-ECD, while GC-MS was used for confirmatory purposes. OCP's groups like ∑HCH, ∑DDT, endosulfan and aldrin were observed in this well-field. Concentration of OCPs from Ranney well exceeded the limit (1 μg l⁻¹) prescribed by the Bureau of Indian Standards (BIS) in pre-monsoon season, though OCP levels in borewells were within BIS limits. However, these levels were very close to the World Health Organisation (WHO) and European Union (EU) limit of for pesticides (0.5 μg l⁻¹) in many samples. Borewell produced better quality water compared to the water from Ranney wells. Although, the level of OCP's was slightly lower than prescribed limit of national regulatory agency but such low doses may cause long-term damage to human populations if such water is consumed for longer durations. At low doses OCP's acts as endocrine disrupting agent and cause metabolic disorders in local population.

CLIPS based decision support system for water distribution networks

Thu, 27 Oct 2011 00:00:00 +0200

CLIPS based decision support system for water distribution networks

Drinking Water Engineering and Science, 4, 37-50, 2011

Author(s): K. Sandeep and K. Rakesh

The difficulty in knowledge representation of a water distribution network (WDN) problem has contributed to the limited use of artificial intelligence (AI) based expert systems (ES) in the management of these networks. This paper presents a design of a Decision Support System (DSS) that facilitates "on-demand'' knowledge generation by utilizing results of simulation runs of a suitably calibrated and validated hydraulic model of an existing aged WDN corresponding to emergent or even hypothetical but likely scenarios. The DSS augments the capability of a conventional expert system by integrating together the hydraulic modelling features with heuristics based knowledge of experts under a common, rules based, expert shell named CLIPS (C Language Integrated Production System). In contrast to previous ES, the knowledge base of the DSS has been designed to be dynamic by superimposing CLIPS on Structured Query Language (SQL). The proposed ES has an inbuilt calibration module that enables calibration of an existing (aged) WDN for the unknown, and unobservable, Hazen-Williams C-values. In addition, the daily run and simulation modules of the proposed ES further enable the CLIPS inference engine to evaluate the network performance for any emergent or suggested test scenarios. An additional feature of the proposed design is that the DSS integrates computational platforms such as MATLAB, open source Geographical Information System (GIS), and a relational database management system (RDBMS) working under the umbrella of the Microsoft Visual Studio based common user interface. The paper also discusses implementation of the proposed framework on a case study and clearly demonstrates the utility of the application as an able aide for effective management of the study network.

Effects of ozonation and temperature on the biodegradation of natural organic matter in biological granular activated carbon filters

Fri, 28 Jan 2011 00:00:00 +0100

Effects of ozonation and temperature on the biodegradation of natural organic matter in biological granular activated carbon filters

Drinking Water Engineering and Science, 4, 25-35, 2011

Author(s): L. T. J. van der Aa, L. C. Rietveld, and J. C. van Dijk

Four pilot (biological) granular activated carbon ((B)GAC) filters were operated to quantify the effects of ozonation and water temperature on the biodegradation of natural organic matter (NOM) in (B)GAC filters. The removal of dissolved organic carbon (DOC), assimilable organic carbon (AOC) and oxygen and the production of carbon dioxide were taken as indicators for NOM biodegradation. Ozonation stimulated DOC and AOC removal in the BGAC filters, but had no significant effect on oxygen consumption or carbon dioxide production. The temperature had no significant effect on DOC and AOC removal, while it had a positive effect on oxygen consumption and carbon dioxide production. Multivariate linear regression was used to quantify these relationships. In summer, the ratio between oxygen consumption and DOC removal was approximately 2 times the theoretical maximum of 2.6 g O₂ g C⁻¹ and the ratio between carbon dioxide production and DOC removal was approximately 1.5 times the theoretical maximum of 3.7 g CO₂ g C⁻¹. The production and loss of biomass, the degassing of (B)GAC filters, the decrease in the NOM reduction degree and the temperature effects on NOM adsorption could only partly explain these excesses and the non-correlation between DOC and AOC removal and oxygen consumption and carbon dioxide production. It was demonstrated that bioregeneration of NOM could explain the excesses and the non-correlation. Therefore, it was likely that bioregeneration of NOM did occur in the (B)GAC pilot filters.

Water supply project feasibilities in fringe areas of Kolkata, India

Mon, 17 Jan 2011 00:00:00 +0100

Water supply project feasibilities in fringe areas of Kolkata, India

Drinking Water Engineering and Science, 4, 9-23, 2011

Author(s): K. Dutta Roy, B. Thakur, T. S. Konar, and S. N. Chakrabarty

Water supply management to the peri-urban areas of the developing world is a complex task due to migration, infrastructure and paucity of fund. A cost-benefit methodology particularly suitable for the peri-urban areas has been developed for the city of Kolkata, India. The costs are estimated based on a neural network estimate. The water quality of the area is estimated from samples and a water quality index has been prepared. A questionnaire survey in the area has been conducted for relevant information like income, awareness and willingness to pay for safe drinking water. A factor analysis has been conducted for distinguishing the important factors of the survey and subsequent multiple regressions have been conducted for finding the relationships for the willingness to pay. A system dynamics model has been conducted to estimate the trend of increase of willingness to pay with the urbanizations in the peri-urban areas. A cost benefit analysis with the impact of time value of money has been executed. The risk and uncertainty of the project is investigated by Monte Carlos simulation and tornado diagrams. It has been found that the projects that are normally rejected in standard cost benefit analysis would be accepted if the impacts of urbanizations in the peri-urban areas are considered.

Metals releases and disinfection byproduct formation in domestic wells following shock chlorination

Tue, 04 Jan 2011 00:00:00 +0100

Metals releases and disinfection byproduct formation in domestic wells following shock chlorination

Drinking Water Engineering and Science, 4, 1-8, 2011

Author(s): M. Walker and J. Newman

Shock chlorination is used for rapid disinfection to control pathogens and nuisance bacteria in domestic wells. A typical shock chlorination procedure involves adding sodium hypochlorite in liquid bleach solutions to achieve concentrations of free chlorine of up to 200 mg L⁻¹ in the standing water of a well. The change in pH and oxidation potential may bring trace metals from aquifer materials into solution and chlorine may react with dissolved organic carbon to form disinfection byproducts. We carried out experiments with four wells to observe and determine the persistence of increased concentrations of metals and disinfection byproducts. Water samples from shock chlorinated wells were analyzed for Pb, Cu, As, radionuclides and disinfection byproducts (haloacetic acids and trihalomethanes), immediately prior to treatment, after sufficient treatment time with chlorine had elapsed, and at intervals determined by the number of casing volumes purged, for up to four times the well casing volume.

Elevated concentrations of lead and copper dissipated in proportion to free chlorine (measured semi-quantitatively) during the purging process. Trihalomethanes and haloacetic acids were formed in wells during disinfection. In one of two wells tested, disinfection byproducts dissipated in proportion to free chlorine during purging. However, one well retained disinfection byproducts and free chlorine after 4 WV had been purged. Although metals returned to background concentrations in this well, disinfection byproducts remained elevated, though below the MCL. This may have been due to well construction characteristics and interactions with aquifer materials. Simple chlorine test strips may be a useful method for indicating when purging is adequate to remove metals and disinfection by-products mobilized and formed by shock chlorination.

Monitoring water distribution systems: understanding and managing sensor networks

Mon, 27 Sep 2010 00:00:00 +0200

Monitoring water distribution systems: understanding and managing sensor networks

Drinking Water Engineering and Science, 3, 107-113, 2010

Author(s): D. D. Ediriweera and I. W. Marshall

Sensor networks are currently being trialed by the water distribution industry for monitoring complex distribution infrastructure. The paper presents an investigation in to the architecture and performance of a sensor system deployed for monitoring such a distribution network. The study reveals lapses in systems design and management, resulting in a fifth of the data being either missing or erroneous. Findings identify the importance of undertaking in-depth consideration of all aspects of a large sensor system with access to either expertise on every detail, or to reference manuals capable of transferring the knowledge to non-specialists. First steps towards defining a set of such guidelines are presented here, with supporting evidence.

Negative pressures in full-scale distribution system: field investigation, modelling, estimation of intrusion volumes and risk for public health

Fri, 16 Jul 2010 00:00:00 +0200

Negative pressures in full-scale distribution system: field investigation, modelling, estimation of intrusion volumes and risk for public health

Drinking Water Engineering and Science, 3, 101-106, 2010

Author(s): M. C. Besner, G. Ebacher, B. S. Jung, B. Karney, J. Lavoie, P. Payment, and M. Prévost

Various investigations encompassing microbial characterization of external sources of contamination (soil and trenchwater surrounding water mains, flooded air-valve vaults), field pressure monitoring, and hydraulic and transient analyses were conducted in the same distribution system where two epidemiological studies showing an increase in gastrointestinal illness for people drinking tap water were conducted in the 1990's. Interesting results include the detection of microorganisms indicators of fecal contamination in all external sources investigated but at a higher frequency in the water from flooded air-valve vaults, and the recording of 18 negative pressure events in the distribution system during a 17-month monitoring period. Transient analysis of this large and complex distribution system was challenging and highlighted the need to consider field pressure data in the process.

MUWS (Microbiology in Urban Water Systems) – an interdisciplinary approach to study microbial communities in urban water systems

Mon, 12 Jul 2010 00:00:00 +0200

MUWS (Microbiology in Urban Water Systems) – an interdisciplinary approach to study microbial communities in urban water systems

Drinking Water Engineering and Science, 3, 91-99, 2010

Author(s): P. Deines, R. Sekar, H. S. Jensen, S. Tait, J. B. Boxall, A. M. Osborn, and C. A. Biggs

Microbiology in Urban Water Systems (MUWS) is an integrated project, which aims to characterize the microorganisms found in both potable water distribution systems and sewer networks. These large infrastructure systems have a major impact on our quality of life, and despite the importance of these systems as major components of the water cycle, little is known about their microbial ecology. Potable water distribution systems and sewer networks are both large, highly interconnected, dynamic, subject to time and varying inputs and demands, and difficult to control. Their performance also faces increasing loading due to increasing urbanization and longer-term environmental changes. Therefore, understanding the link between microbial ecology and any potential impacts on short or long-term engineering performance within urban water infrastructure systems is important. By combining the strengths and research expertise of civil-, biochemical engineers and molecular microbial ecologists, we ultimately aim to link microbial community abundance, diversity and function to physical and engineering variables so that novel insights into the performance and management of both water distribution systems and sewer networks can be explored. By presenting the details and principals behind the molecular microbiological techniques that we use, this paper demonstrates the potential of an integrated approach to better understand how urban water system function, and so meet future challenges.

Water quality and treatment of river bank filtrate

Thu, 17 Jun 2010 00:00:00 +0200

Water quality and treatment of river bank filtrate

Drinking Water Engineering and Science, 3, 79-90, 2010

Author(s): W. W. J. M. de Vet, C. C. A. van Genuchten, M. C. M. van Loosdrecht, and J. C. van Dijk

In drinking water production, river bank filtration has the advantages of dampening peak concentrations of many dissolved components, substantially removing many micropollutants and removing, virtually completely, the pathogens and suspended solids. The production aquifer is not only fed by the river bank infiltrate but also by water percolating through covering layers. In the polder areas, these top layers consist of peat and deposits from river sediments and sea intrusions.

This paper discusses the origin and fate of macro components in river bank filtrate, based on extensive full-scale measurements in well fields and treatment systems of the Drinking Water Company Oasen in the Netherlands. First, it clarifies and illustrates redox reactions and the mixing of river bank filtrate and PW as the dominant processes determining the raw water quality for drinking water production. Next, full-scale results are elaborated on to evaluate trickling filtration as an efficient and proven one-step process to remove methane, iron, ammonium and manganese. The interaction of methane and manganese removal with nitrification in these systems is further analyzed. Methane is mostly stripped during trickling filtration and its removal hardly interferes with nitrification. Under specific conditions, microbial manganese removal may play a dominant role.

I-WARP: Individual Water mAin Renewal Planner

Tue, 18 May 2010 00:00:00 +0200

I-WARP: Individual Water mAin Renewal Planner

Drinking Water Engineering and Science, 3, 71-77, 2010

Author(s): Y. Kleiner and B. Rajani

I-WARP is based upon a nonhomogeneous Poisson approach to model breakage rates in individual water mains. The structural deterioration of water mains and their subsequent failure are affected by many factors, both static (e.g., pipe material, pipe size, age (vintage), soil type) and dynamic (e.g., climate, cathodic protection, pressure zone changes). I-WARP allows for the consideration of both static and dynamic factors in the statistical analysis of historical breakage patterns. This paper describes the mathematical approach and demonstrates its application with the help of a case study. The research project within which I-WARP was developed, was jointly funded by the National Research Council of Canada (NRC), and the Water Research foundation (formerly known as the American Water Works Association Research Foundation – AwwaRF) and supported by water utilities from USA and Canada.

Fluorescence spectroscopy as a tool for determination of organic matter removal efficiency at water treatment works

Thu, 29 Apr 2010 00:00:00 +0200

Fluorescence spectroscopy as a tool for determination of organic matter removal efficiency at water treatment works

Drinking Water Engineering and Science, 3, 63-70, 2010

Author(s): M. Z. Bieroza, J. Bridgeman, and A. Baker

Organic matter (OM) in drinking water treatment is a common impediment responsible for increased coagulant and disinfectant dosages, formation of carcinogenic disinfection-by products, and microbial re-growth in distribution system. The inherent heterogeneity of OM implies the utilization of advanced analytical techniques for its characterization and assessment of removal efficiency. Here, the application of simple fluorescence excitation-emission technique to OM characterization in drinking water treatment is presented. The fluorescence data of raw and clarified water was obtained from 16 drinking water treatment works. The reduction in fulvic-like fluorescence was found to significantly correlate with OM removal measured with total organic carbon (TOC). Fluorescence properties, fulvic- and tryptophan-like regions, were found to discriminate OM fractions of different removal efficiencies. The results obtained in the study show that fluorescence spectroscopy provides a rapid and accurate characterization and quantification of OM fractions and indication of their treatability in conventional water treatment.

NOM characterization and removal at six Southern African water treatment plants

Thu, 15 Apr 2010 00:00:00 +0200

NOM characterization and removal at six Southern African water treatment plants

Drinking Water Engineering and Science, 3, 53-61, 2010

Author(s): J. Haarhoff, M. Kubare, B. Mamba, R. Krause, T. Nkambule, B. Matsebula, and J. Menge

Organic pollution is a major concern during drinking water treatment. Major challenges attributed to organic pollution include the proliferation of pathogenic micro-organisms, prevalence of toxic and physiologically disruptive organic micro-pollutants, and quality deterioration in water distribution systems. A major component of organic pollution is natural organic matter (NOM). The operational mechanisms of most unit processes are well understood. However, their interaction with NOM is still the subject of scientific research. This paper takes the form of a meta-study to capture some of the experiences with NOM monitoring and analysis at a number of Southern African Water Treatment Plants. It is written from the perspective of practical process selection, to try and coax some pointers from the available data for the design of more detailed pilot work. NOM was tracked at six water treatment plants using dissolved organic carbon (DOC) measurements. Fractionation of the DOC based on biodegradability and molecular weight distribution was done at a water treatment plant in Namibia. A third fractionation technique using ion exchange resins was used to assess the impact of ozonation on DOC. DOC measurements alone did not give much insight into NOM evolution through the treatment train. The more detailed characterization techniques showed that different unit processes preferentially remove different NOM fractions. Therefore these techniques provide better information for process design and optimisation than the DOC measurement which is routinely done during full scale operation at these water treatment plants.

A bottom-up approach of stochastic demand allocation in water quality modelling

Thu, 15 Apr 2010 00:00:00 +0200

A bottom-up approach of stochastic demand allocation in water quality modelling

Drinking Water Engineering and Science, 3, 43-51, 2010

Author(s): E. J. M. Blokker, J. H. G. Vreeburg, H. Beverloo, M. Klein Arfman, and J. C. van Dijk

An "all pipes" hydraulic model of a drinking water distribution system was constructed with two types of demand allocations. One is constructed with the conventional top-down approach, i.e. a demand multiplier pattern from the booster station is allocated to all demand nodes with a correction factor to account for the average water demand on that node. The other is constructed with a bottom-up approach of demand allocation, i.e., each individual home is represented by one demand node with its own stochastic water demand pattern. This was done for a drinking water distribution system of approximately 10 km of mains and serving ca. 1000 homes. The system was tested in a real life situation.

The stochastic water demand patterns were constructed with the end-use model SIMDEUM on a per second basis and per individual home. Before applying the demand patterns in a network model, some temporal aggregation was done. The flow entering the test area was measured and a tracer test with sodium chloride was performed to determine travel times. The two models were validated on the total sum of demands and on travel times.

The study showed that the bottom-up approach leads to realistic water demand patterns and travel times, without the need for any flow measurements or calibration. In the periphery of the drinking water distribution system it is not possible to calibrate models on pressure, because head losses are too low. The study shows that in the periphery it is also difficult to calibrate on water quality (e.g. with tracer measurements), as a consequence of the high variability between days. The stochastic approach of hydraulic modelling gives insight into the variability of travel times as an added feature beyond the conventional way of modelling.

Rapid evaluation of water supply project feasibility in Kolkata, India

Wed, 31 Mar 2010 00:00:00 +0200

Rapid evaluation of water supply project feasibility in Kolkata, India

Drinking Water Engineering and Science, 3, 29-42, 2010

Author(s): K. Dutta Roy, B. Thakur, T. S. Konar, and S. N. Chakrabarty

Mega cities in developing countries are mostly dependent on external funding for improving the civic infrastructures like water supply. International and sometimes national agencies stipulate financial justifications for infrastructure funding. Expansion of drinking water network with external funding therefore requires explicit economic estimates. A methodology suitable for local condition has been developed in this study. Relevant field data were collected for estimating the cost of supply. The artificial neural network technique has been used for cost estimate. The willingness to pay survey has been used for estimating the benefits. Cost and benefit have been compared with consideration of time value of money. The risk and uncertainty have been investigated by Monte Carlo's simulation and sensitivity analysis. The results in this case indicated that consumers were willing to pay for supply of drinking water. It has been also found that supply up to 20 km from the treatment plant is economical after which new plants should be considered. The study would help to plan for economically optimal improvement of water supply. It could be also used for estimating the water tariff structure for the city.

Online modelling of water distribution systems: a UK case study

Tue, 30 Mar 2010 00:00:00 +0200

Online modelling of water distribution systems: a UK case study

Drinking Water Engineering and Science, 3, 21-27, 2010

Author(s): J. Machell, S. R. Mounce, and J. B. Boxall

Hydraulic simulation models of water distribution networks are routinely used for operational investigations and network design purposes. However, their full potential is often never realised because, in the majority of cases, they have been calibrated with data collected manually from the field during a single historic time period and, as such, reflect the network operational conditions that were prevalent at that time, and they are then applied as part of a reactive, desktop investigation. In order to use a hydraulic model to assist proactive distribution network management its element asset information must be up to date and it should be able to access current network information to drive simulations. Historically this advance has been restricted by the high cost of collecting and transferring the necessary field measurements. However, recent innovation and cost reductions associated with data transfer is resulting in collection of data from increasing numbers of sensors in water supply systems, and automatic transfer of the data to point of use. This means engineers potentially have access to a constant stream of current network data that enables a new era of "on-line" modelling that can be used to continually assess standards of service compliance for pressure and reduce the impact of network events, such as mains bursts, on customers. A case study is presented here that shows how an online modelling system can give timely warning of changes from normal network operation, providing capacity to minimise customer impact.

Impact of decreasing water demand on bank filtration in Saxony, Germany

Fri, 29 Jan 2010 00:00:00 +0100

Impact of decreasing water demand on bank filtration in Saxony, Germany

Drinking Water Engineering and Science, 3, 11-20, 2010

Author(s): T. Grischek, D. Schoenheinz, C. Syhre, and K. Saupe

Bank filtration has been of great importance to the drinking water supply in Germany for many decades. The water quality of pumped raw water from bank filtration sites depends to a high degree on the water quality of the infiltrating surface water and the landside groundwater, the mixed portion of both, as well as the flow and transport conditions in the aquifer. Following the improvement of river water quality and a drastic decrease in water demand during the last 20 years in Germany, the influence of landside groundwater quality has become more important for the raw water quality of waterworks relying on bank filtration. The hydrogeologic analysis of three bank filtration sites in Saxony and the management of abstraction rates and well operation in response to fluctuating water demand are discussed.

NOM removal technologies – Norwegian experiences

Wed, 13 Jan 2010 00:00:00 +0100

NOM removal technologies – Norwegian experiences

Drinking Water Engineering and Science, 3, 1-9, 2010

Author(s): H. Ødegaard, S. Østerhus, E. Melin, and B. Eikebrokk

The paper gives an overview of the methods for removal of natural organic matter (NOM) in water, particularly humic substances (HS), with focus on the Norwegian experiences. It is demonstrated that humic substances may be removed by a variety of methods, such as; molecular sieving through nanofiltration membranes, coagulation with subsequent floc separation (including granular media or membrane filtration), oxidation followed by biofiltration and sorption processes including chemisorption (ion exchange) and physical adsorption (activated carbon). All these processes are in use in Norway and the paper gives an overview of the operational experiences.