bluuebunny/crossref_metadata_2025 huggingface dataset:
Pre-treatment with dissolved air flotation considering an integrated process design
Authors: Dahlquist J. , Kulesza M.
Published: May 2018

The raw water from Lake Zegrzynski is difficult to treat and requires a high chemical dosing rate of coagulant for the reduction of organic matter in order to comply with EU standards. The high degree of reduction calls for an efficient coagulant, but also an optimal chemistry such as correct dosing amount and an optimal flocculation-pH. The paper describes different removal efficiencies of organic matter, particularly with respect to pH in flocculation.

During the warm season, the raw water can also suffer from large amounts of plankton that are difficult to remove to a satisfactory degree. In a two-step chemical treatment concept, with Dissolved Air Flotation (DAF) and the pulsator process, the plankton content in the final outlet water is reduced to very low levels. It follows that eventual peaks of plankton in the raw water cannot be detected in the final outlet water.

Ozone is added for removal of taste and odour originating from the presence of plankton. In the pre-treatment step prior to the ozonation, a great deal of the organic matter is removed, which reduces the necessary ozone dosage.

The Municipal Water Company of Warsaw City has decided to consider an additional pre-treatment step to the existing water treatment plant at Wieliszew. For that purpose, and bearing in mind an integrated process design, the company has performed pilot-scale experiments with DAF installed prior to a process line identical with the existing full-scale plant. The experimental flow is about 10 m3/h.
Removal of natural organic matter (NOM) using different coagulants and lightweight expanded clay aggregate filters
Authors: Eikebrokk Bjørnar , Saltnes Torgeir
Published: May 2018

Chitosan and lightweight expanded clay aggregates were investigated as alternatives to traditional metal coagulants and anthracite in pilot scale coagulation-filtration experiments for the removal of natural organic matter (NOM) from drinking water. The raw water tested covered a range of colour and organic carbon of 15–50 mg Pt/L and 2–5 mg NPOC, respectively. Aluminium sulphate, poly aluminium chlorides with different calcium content, iron chloride sulphate, and chitosan coagulants were tested. The dual media filter bed was built with 0.6 m of 0.8–1.6 mm lightweight expanded clay aggregates (Filtralite) above 0.35 m of 0.4–0.8 mm sand. A conventional anthracite-sand filter with the same layer depths and grain sizes was used as a reference. In general, the maximum permissible concentration level of 0.1-mg Me/L controlled the minimum coagulant dose requirements when metal-based coagulants were used (Norwegian water quality standard). Typical NOM removal efficiencies obtained with metal coagulantswere in the range of 75–90% and 40–70% with respect to colour and organic carbon, respectively. Chitosan was able to remove colour quite effectively, but this coagulant was less effective with respect to organic carbon removal. Lightweight expanded clay aggregate was a good alternative to anthracite, with lower rates of head loss build-up, and increased filter run length and filter storage capacity. Only small differences in effluent water quality were detected with the two filters.
Metabolic activity test in investigation of biodegradation in biological filters
Authors: Kijowska E. , Leszczyńska M. , Sozański M.M.
Published: May 2018

The esterase activity (EA) metabolic activity test was shown to be applicable to measurement of the activity of biomass of biofilters. The method was reproducible and detected significant differences in biomass activity in different filters and at various depths within each filter. The highest biomass activity occurred at the bed surface in 60% of filter media. The EA test also revealed the changes of biomass activity during the time of filter operation as a result of backwashing. For all investigated filters maximum biomass activity in the middle of washing cycle was observed. Following backwashing, the activity dropped to a minimum. The relation between TOC (total organic carbon) and COD (chemical oxygen demand) removal and biomass activity were noted. The results presented in the paper suggest that the metabolic activity test can be used in investigation of the performance of biofilters.
Technical-economic analysis of water distribution networks
Authors: Barsan Em. , Ignat C.
Published: May 2018

For water distribution networks two type of analysis are performed: 1 - hydraulic analysis or the balancing of the network and 2 - technical-economic analysis or the network sizing. In technical-economic analysis the hydraulic condition (the continuity of flow rate at nodes and energy conservation in independent loops) is added and economic conditions (minimum annual expenses for construction and operation). In these conditions, the technical-economic analysis represents a nonlinear programming problem with equality restraint (relation 11-13) which transforms into a nonlinear system (relation 15-17) with which we determine flow rates and head losses on pipelines. This system has in its construction the hydraulic conditions (relation 16,17) and “economical” conditions (relation 18,21) both being written in the same way. In the case when the objective function W (relation 1) is convex the establishing of flow rates and head losses is done directly, but in the case when the same function is concave-convex it is necessary to have an intermediate step. By relation 10 it obtains the theoretical diameters which will be adjusted to meet commercial ones. In the paper is presented a model and a methodology for the application of the technical-economic analysis to the water distribution networks, and a mode of utilization for a practical example.
The role of pipe ageing in copper corrosion by-product release
Authors: Edwards M. , Powers K. , Hidmi L. , Schock M.R.
Published: May 2018

The presence of sulphate, bicarbonate and orthophosphate can change the type of solid present in systems containing cupric ion or cupric hydroxide solids. In some cases, a short-term reduction in copper solubility is realized, but over longer periods of time formation of basic cupric sulphate (brochantite) and even cupric phosphate can ultimately prevent the formation of very insoluble tenorite or malachite phases. To the extent that this occurs, the presence of sulphate and phosphate in water can increase copper solubility over much longer time periods. The relative effect can depend on the anion concentration and the rate of solids precipitation. Low levels of sulphate tend to hasten the transition from cupric hydroxide to tenorite, whereas higher levels of sulphate can interfere with that transition. These possible effects should be considered when attempting to reduce copper corrosion by-product release from consumer plumbing and similar transitions are likely important for other plumbing materials such as zinc, iron and lead.
Biomass production potential of materials in contact with drinking water: method and practical importance
Authors: van der Kooij D. , Veenendaal H.R.
Published: May 2018

Synthetic materials in contact with drinking water may affect microbial water quality by releasing growth-promoting substances. Various tests are being used for assessing the microbial growth-supporting potential of such materials. The biofilm formation potential (BFP) method is based on determining the concentration of active biomass (as adenosine triphosphate (ATP)) on the surface of a material incubated in slow sand filtrate (surface to volume ratio 0.15/cm) at 25°C during a period of 16 weeks. In addition to attached biomass (biofilm), suspended biomass is also produced. The amount of suspended biomass is a significant fraction (20-70%) of the total biomass production, depending of the type of material. Therefore, it is concluded that the production of suspended biomass should be included in evaluating the growth-promoting properties of materials in contact with drinking water. Consequently, the BFP test has been adapted to the biomass production potential (BPP) test, with BPP including BFP and suspended biomass production (SBP), as pg ATP/cm2. The defining criteria for BPP values for materials require further investigation into the effects of water quality on biofilm formation and the relationship between BPP values and regrowth problems.
Assessment of membrane processes for taste and odour removal
Authors: Laîne J.-M. , Glucina K. , Malleret L. , Bruchet A. , Baudin I. , Jacangelo J.G.
Published: May 2018

The occurrence of tastes and odours (T&O) in potable water is considered one of the main problems by the drinking water companies. Thus, several treatment processes have been developed over the years to control T&O, including air stripping, activated carbon and oxidation using ozone. However, little information is available in the literature on the use of membranes for T&O removal. Therefore, the objective of this paper is to present potential of membrane processes for the removal of taste and odour-causing compounds. Several membranes were tested including ultrafiltration (UF), UF combined with powdered activated carbon (PAC), nanofiltration (NF) and low pressure reverse osmosis (LP RO) membranes. Combination of UF with PAC was found to be effective for T&O control. The use of NF or LP RO is still unclear in the objective of T&O control.
Ozone: its effect on coagulation and filtration
Authors: Becker W.C. , O'Melia C.R.
Published: May 2018

The interest in ozone for drinking water treatment in the United States has increased dramatically in recent years due to new regulations and concern over Cryptosporidium. Ozone has many benefits, however, its expense is significant and its placement in the treatment train should be chosen with a sound understanding of its effect on other unit processes. The goal of this paper is to provide an overview of the effect of ozone on the coagulation and filtration processes. This is important given the enhanced coagulation requirements of the disinfection by-product rule and the filtered water quality goals of the Partnership for Safe Water. The effect of ozone on coagulation is shown to be dependent on the coagulant type and on the water quality characteristic that is setting the optimum coagulant dose. For waters with moderate to high dissolved organic carbon (DOC) levels, the coagulant dose is set by the DOC. Ozonation converts NOM into smaller, more oxygenated compounds, e.g. oxalic acid, that exert a greater metal salt coagulant demand than the parent compounds. In this case, higher dosages of alum or ferric chloride are needed. For low DOC waters, the coagulant dose is set by the particle and the adsorbed organic matter. Ozone may react with adsorbed DOC and alter the amount and conformation of adsorbed organic matter, which can lead to a decrease in the optimum coagulant dose. Finally, because cationic polymers react with particles and large organic matter (and not the smaller compounds formed after ozonation), the optimum polyelectrolyte coagulant dose after ozonation is reduced. Ozonation prior to filtration (intermediate ozonation) is shown to be beneficial for significantly reducing filtered water particle counts by as much as an order of magnitude.
Characterization of suspended particles and deposits in drinking water reservoirs
Authors: Gauthier V. , Portal J.M. , Yvon J. , Rosin C. , Block J.C. , Lahoussine V. , Benabdallah S. , Cavard J. , Gatel D. , Fass S.
Published: May 2018

Suspended particles transported by drinking water were examined to understand their role in deposit accumulation and colonization in pilot and full-scale reservoirs. No pesticides were detected in the deposits but several PAH were identified. Deposits accumulated at a rate of 8 μg/cm2/day (29 g/m2/year) over a five month period. Quartz, feldspar, and amorphous iron were characterized in reservoir sediments. Sedimentation of suspended particles, mainly those composed of organic (biological) matter, was incomplete, and was not a key factor governing bacterial accumulation in the deposits (104 to 105 CFU/ cm2). Thus, limiting bacterial nutrients - dissolved organic matter - in treated water should be the only way to control the extent of bacterial colonization of deposits.
Chlorinated solvents cometabolism by an enriched nitrifying bacterial consortium
Authors: Ginstet P. , Audic J.M. , Block J.C.
Published: May 2018

The biodegradability of three of the most frequently halogenated aliphatics (trichloroethene, chloroform and 1.1.1.-trichloroethane) found in drinking water aquifers by a nitrifying enriched mixed biomass was investigated during batch tests. Within this mixed biomass, ammonia oxidisers were the effective degraders. The presence of ammonia stimulated chlorocarbon biodegradation, and the presence of chlorocarbon inhibited ammonia oxidation. This contrasted phenomenon was explained by a balance between electron supply from ammonia necessary to sustain the chlorocarbon oxidation and competitive inhibition for the ammonia monooxygenase active site between both substrates. About 0.03 to 0.2% of the electrons generated by ammonia oxidation were used for chlorocarbon degradation. Trichloroethene and chloroform oxidation induced a biomass inactivation (around 30 to 40 mg of proteins inactivated per μmol of chlorocarbn oxidised). Biomass re-activation due to exergonic ammonia catabolism was estimated to 24±6 mg of proteins reactivated per mmol of ammonia oxidised in both cases. No inactivation of re-activation was observed in the case of 1.1.1-trichloroethane.
Kinetic analysis of nitrifying biofilm growing on the rotating membrane disk
Authors: Kimura K. , Watanabe Y. , Okabe S. , Satoh H.
Published: May 2018

The authors have proposed a novel water treatment process in which nitrifying bacteria are fixed on the surface of rotating membrane disks. This biofilm-membrane process can perform strict solid-liquid separation and oxidation of ammonia nitrogen simultaneously. In this research, applicability of the conventional biofilm model (assuming the biofilm structure to be flat, homogeneous and continuous) to analysis of the biofilm developing in the proposed process was examined. A long-term operation for culturing the active nitrifying biofilm was carried out prior to kinetic investigation. By cryosectioning of the biofilm and image analysis, the thickness of the biofilm was determined to be 87 μm. From this biofilm thickness and the result of the batch ammonia consumption test, the intrinsic zero-order ammonia consumption rate of the biofilm was estimated precisely to be 930 g/m3/h. Using these parameters, the ammonia concentration profile in the biofilm was calculated by the conventional model, and the applicability of the model was examined by comparing the calculated profile with the ones measured with a microelectrode. The calculated profile was very close to the measured ones, which indicated feasibility of the conventional model to the analysis of the biofilm grown in the proposed process. The studied biofilm actually had a simple, i.e. flat, homogeneous and continuous, structure due to membrane filtration. This was the reason why the conventional model could still be employed. In the analysis of the data dealing with low concentrations of ammonia, however, first-order kinetics should be used. The first-order ammonia consumption rate constant of the studied biofilm was estimated to be 808 h-1.
Relating complex solute mixture characteristics to membrane fouling
Authors: Wright S. , Ranville J. , Amy G.
Published: May 2018

This paper presents a concept for relating complex solute mixture characteristics to membrane fouling using field flow fractionation. Field flow fractionation has traditionally been used in separation science as a tool for characterizing aquatic system components in terms of size based on Stokes-Einstein theory. This work begins to assess the possibility of using flow field flow fractionation (FlFFF) as a tool for ‘fingerprinting’ complex solute mixtures and obtaining effective mixture properties, such as effective size, effective diffusion coefficient, and interaction potential between solutes and ultrafiltration membrane materials. The effect of applied field and changes in solute ionic strength are demonstrated for polystyrene sulfonate latex colloids. Quantitative analysis is also considered for the residence time distribution (commonly referred to as a fractogram) of solutes from FlFFF measurements. The results here suggest that FlFFF may effectively fingerprint a complex solute mixture based on solute characteristics and membrane solute interactions.
A study on the PP hollow fiber membrane contactor and its performance for removing ammonia from wastewater or mixed gas: II. Ammonia removal from mixed gas
Authors: Wang J. , Xu Y. , Xu Z. , Xu H.
Published: May 2018

In this paper, we briefly discussed the utilization of the PP HFM contactor for removal of gaseous ammonia directly from mixed gas in ammonia manufacture in order to find an economic way to substitute conventional soft-water washing absorption technology. The Hollow Fiber Membrane (HFM) contactor has very high elimination (99.9%) under optimum operation conditions. 5.1 Nm3/(m2.h) gas treatment ability can be achieved, as outlet and inlet ammonia concentration are 0.02 g/Nm3 and 20.0 g/Nm3 respectively and gas stay-time in the contactor is only 0.04 s when acid supply around the membrane is sufficient. The results of industrial tests indicated that this technology could be used to eliminate mixed gas containing ammonia and replace conventional soft-water washing and absorption techniques.
Fouling of ultrafiltration membranes in drinking water treatment of karstic spring waters
Authors: Hagmeyer G. , Gimbel R.
Published: May 2018

Three UF-systems were tested for the drinking water treatment of karstic spring water. The pilot plants were operated in Marmagen, which is located in North-Rhine Westfalia (Germany). One of the two tested capillary UF-systems (in-out mode) was backflushed with filtrate and with filtrate and hydrogen peroxide. The other one could be flushed with air and raw water (forward flush) before a backflush was performed. The third system was an immersed UF-system (out-in) where negative pressure on the filtrate side is applied. The capillary UF-systems were operated at high flux and long backflush intervals when turbidity was low. At high turbidities the permeability declined and could only be restored by chemical cleaning. For this particular water the immersed system showed also a permeability decline, which was less pronounced. The permeability recovered in normal operation, when the turbidity declined. Using SEM and EDX the fouling could be mainly attributed to small particles (well below 3 μm). Qualitative element analysis showed that silica is the main component of the formed cake layer.
Comparison of surface water pre-treatments for ultrafiltration
Authors: Drage B. , Holden P. , Marchant J. , Bailey A. , Upton J.
Published: May 2018

The River Trent runs through both Severn Trent and Anglian Water regions, and has been identified as a potential new water resource for both companies. It contains treated effluent from 4 million people and industry in the Midlands. As part of an ongoing project, comparing conventional water treatment processes with membrane technologies for treatment of the River Trent to potable standards, pre-treatment processes for ultrafiltration are being compared. Depth filtration gave the best particulate removal, whereas the package filters performed as per the manufacturers' specifications. Package filters tended to increase the small particulate fraction between 2-5 μm, so although these may remove problems caused by large particles they could aggravate pore blocking and membrane penetration related fouling. There is a direct trade off between the capital cost of pre-treatments vs. increased running costs (higher TMPs, more frequent cleaning, extensive cleaning requirements).
Arsenic treatment technology for groundwaters
Authors: Selvin N. , Upton J. , Sims J. , Barnes J.
Published: May 2018

The new United Kingdom drinking water standard of 10 μg/l arsenic will become a statutory obligation in 2003. To comply with the new standard, Severn Trent Water will require a new treatment process to be installed at 17 groundwater sites. The Company embarked on a development programme in 1995, with pilot studies commencing in 1996. Investigations have covered a range of potential treatment technologies including coagulation, ion exchange, reverse osmosis and adsorption. Adsorption with granular ferric media was found to be the best available technology for treating groundwater in Severn Trent.

The paper details the development work undertaken, which has focused on the evaluation of aluminium and ferric based granular medias. This has enabled the design and construction of the first arsenic adsorption plant in the UK, with an output of 20 Ml/d.
OTTER mathematical process simulation of potable water treatment
Authors: Head R. , Shepherd D. , Butt G. , Buck G.
Published: May 2018

Process modelling has been used for many years in the chemical engineering field and more recently has become well established for as a tool for analysing and optimising the performance of wastewater treatment works. In the clean water area, models are routinely used for simulating distribution networks. In contrast, however, the use of modelling tools on potable water treatment works is relatively new and has yet to become well established. A range of tools have been suggested, including artificial neural networks, computational fluid dynamics and process simulation.

WRc have developed a dynamic simulation package for predicting the performance of water treatment works, via models of individual processes. The software has a range of uses, including process and works optimisation, operational decision support, as a design aid and for training engineers and operators. The models are dynamic so that they predict the response of the treatment works to changes in flow, raw water quality and process operating conditions.

The software has been used in a wide variety of applications, including optimising process plant operation to minimise cost and to investigate the reasons why a treatment works failed to meet its design criteria at the maximum design throughput.
Disinfection effects on E. coli using TiO2/UV and solar light system
Authors: Cho I.-H. , Moon I.-Y. , Chung M.-H. , Lee H.-K. , Zoh K.-D.
Published: May 2018

First, a continuous flow TiO2/UV reactor was designed and developed in order to examine E. coli disinfection effect using UV light. The optimum conditions for disinfection such as flow rate, light intensity, TiO2 concentration, initial E. coli concentration were examined. The results are as follow (i) The use of the quartz device and TiO2 (anatase) resulted in killing of E. coil within minutes. (ii) Photocatalytic disinfection with UV light in the presence of TiO2 more effectively killed E. coli than UV or TiO2 adsorption only. (iii) As flow rate increased, the survival ratio of E. coli decreased, but over 3 L/min of flow rate, the efficiency was limited. (iv) E. coli survival ratio decreased linearly with increasing UV light intensity. (v) The dosage of TiO2 affected the E. coli disinfection efficiency, and above 0.1 wt% TiO2 concentration, the disinfection was less effective because TiO2 particles may result in screening off the light. (ri) The disinfection reaction follows first-order kinetics.

Secondly, outdoor experiments with natural sunlight instead of artificial UV light in TiO2 reactors were also conducted to investigate alternative energy source applicability on E. coli disinfection. It is found that the presence of clouds in the sky markedly increased the time required for killing E. coli and the bacteria cells also disappeared with a first-order kinetics. On the basis of these experimental observations, the disinfection of E. coli using TiO2 under solar light irradiation can be a feasible application of the advanced oxidation process.
Cost-effective water treatment of polluted surface water by using direct filtration and granular activated carbon filtration
Authors: Cromphout J. , Rougge W.
Published: May 2018

In Harelbeke a Water Treatment Plant with a capacity of 15,000 m3/day, using Schelde river water has been in operation since April 1995. The treatment process comprises nitrification, dephosphatation by direct filtration, storage into a reservoir, direct filtration, granular activated carbon filtration and disinfection. The design of the three-layer direct filters was based on pilot experiments. The performance of the plant during the five years of operation is discussed. It was found that the removal of atrazin by activated carbon depends on the water temperature.
New approaches for structural characterization of organic matter in drinking water and wastewater effluents
Authors: Drewes J.E. , Croue J.-P.
Published: May 2018

The scope if this work was directed to address potential differences or similarities between natural organic matter (NOM) and effluent organic matter (EfOM) by combining operationally defined categorization protocols with state-of-the-art characterization techniques to investigate the bulk of organics in raw drinking water samples (surface and groundwater) and wastewater samples with respect to origin, size, structure, and functionality. Samples of different drinking water and wastewater prior to and after groundwater recharge from France and the U.S. were considered in this study. The physical, chemical, and biological processes that generate and modify organic compounds in natural and engineered systems share many similarities. As a result, the chemical characteristics of effluent derived and naturally derived organic compounds overlap extensively. However, the aromatic moieties present in the EfOM matrix are probably of different origin than the aromatic moieties of the NOM as indicated by a relationship we have established between SUVA and the aromatic carbon content.
Development of a new method of measuring bubble size
Authors: Han M.Y. , Park Y.H. , Yu T.J.
Published: May 2018

The use of bubbles in water and wastewater treatment, including dissolved air flotation (DAF) and electro-flotation (EF), is attracting much interest recently. These flotation processes are governed by characteristics of the bubbles as well as the particles, and therefore it is necessary to investigate the size distribution of the bubbles that are generated. In this research, a new method has been developed to measure the bubble size, using commercially available batch-type and on-line particle counters. The results are compared with the traditional image analysis method. Although there are some discrepancies, the results show that an on-line particle counter can produce reasonably accurate size distributions conveniently and efficiently. The bubble size measurement technique developed in this study will assist understanding and improvement of the DAF and EF processes, from both theoretical and practical points of view.
Fate and removal of Cryptosporidium in a dissolved air flotation water plant with and without recycle of waste filter backwash water
Authors: Edzwald J.K. , Tobiason J.E.
Published: May 2018

Pilot plant research focused on the removal of Cryptosporidium oocysts by dissolved air flotation (DAF) clarification and by dual media filtration and on the impacts of the recycle of waste filter backwash water containing oocysts. No impacts from recycle of filter backwash (10% rate) were found for turbidity, particle counts (2-15 μm), and UV254 on DAF and filtration performance. DAF achieved Cryptosporidium log removals of 1.6 to 2.2 without or with recycle of filter backwash. No impacts of recycle were found on filtration, and cumulative (DAF plus filtration) log oocyst removals exceeded 4 log. Model predictions show that the fate of Cryptosporidium and the build-up of oocysts in the plant influent depend on: DAF performance, the percent of filtered water production used for backwashing, and the percent of filter backwash recycle flow. A DAF plant using 2.5% of filtered water production for backwashing and achieving 1.6 log removal or greater of oocysts by DAF clarification will not have a build-up of oocysts in the plant influent regardless of the recycle rate.
Determination of mass transport characteristics for natural organic matter (NOM) in ultrafiltration (UF) and nanofiltration (NF) membranes
Authors: Lee S. , Shim Y. , Kim In S. , Sohn J. , Yim S.K. , Cho J.
Published: May 2018

This study is mainly concerned with establishing a reliable method of the quantitative analysis of natural organic matter (NOM) transport characteristics through ultrafiltration (UF) and nanofiltration (NF) membranes with molecular weight cutoffs of 8000 (GM) and 250 (ESNA), respectively. Filtrations were conducted with a cross-flow filtration unit and hydrodynamic operating conditions were controlled by a J0/k ratio (the ratio of initial permeate flux [J0] to a back diffusional mass transfer coefficient [k]). A four-parameter (the apparent mass transfer coefficient [ka], the solute concentration near the membrane surface [Cm], the solute permeability [Pm], and the reflection coefficient (σ) model based on concentration polarization and irreversible thermodynamics was used to manipulate experimental results quantitatively. With the values of the determined parameters, the transport characteristics of NOM due to different solution chemistries such as pH and ionic strength through UF/NF membrane pores were investigated. This model was also used to demonstrate the effects of NOM structure (hydrophobic/transphilic/hydrophilic) on transport through the membranes, with XAD-8/4 resins fractionation and isolation procedures. Four parameters estimated through the model were revealed to be relevant to elucidate the behaviors of NOM in membranes and corresponding transport-related results were in good agreement with the theoretical descriptions related to the interactions between NOM molecules and membrane surface/pores.
The effect of various operating conditions and water quality parameters on the removal of perchlorate in a biologically active carbon filter
Authors: Brown J.C. , Snoeyink V.L. , Raskin L.M. , Chee-Sanford J.C. , Lin R.
Published: May 2018

The removal of μg/L concentrations of perchlorate using biologically active carbon filtration (BAC) was investigated. Previous work has shown that BAC filtration can be a highly effective treatment process for the removal of perchlorate from drinking water. The work presented here demonstrated that perchlorate removal using BAC filtration can be inhibited by dissolved oxygen. It also showed that empty-bed contact time is a key process parameter that affects perchlorate removal in the BAC filter. Finally, it was demonstrated that BAC filtration is robust with respect to electron donor addition failure.
Characterisation of coated sand from iron removal plants
Authors: Sharma S.K. , Petrusevski B. , Schippers J.C.
Published: May 2018

Water treatment plants removing iron from groundwater are commonly expected to operate in oxidation-floc formation mode. However, there are indications that adsorptive iron removal plays a role as well. Adsorptive iron removal has several potential advantages over oxidation-floc formation iron removal. Therefore, the physical and surface chemical characteristics of coated sand from twelve different groundwater treatment plants in the Netherlands were analysed to assess their potential use in adsorptive iron removal. Specific surface areas, amounts of iron, manganese, calcium and TOC in the coatings and iron(II) adsorption capacities of the coated media were measured. Additionally, grain size distribution and density of the media were determined and X-ray diffractograms, scanning electron micrographs and EDAX spectra were prepared. Compared to new sand, coated sand had a very high porosity and a very large specific surface area. The surface extractable iron content of the coated sand increased with iron loading. The iron content of the coatings ranged from 27% to 45%. At pH 6.5, the iron(II) adsorption capacities of different coated sands were 10 to 55 times that of new sand. In general, iron(II) adsorption capacities of the coated sand from different plants increased with the increase in the time in use and the iron content of the coating. However, the average annual increase of iron content of the coatings and the iron adsorption capacity were different for the coated sands from different plants, probably due to the difference in water quality, process conditions applied and time in use. The grain size of the filter sand increased and their density decreased with the development of the coating. The decrease in density was a function of the increase in the effective grain size. EDAX analysis showed that iron and oxygen were the main elements in the coating followed by manganese, calcium, silicon and carbon. All the coatings analysed were X-ray amorphous or poorly crystalline. The measured high adsorption capacities of coated sand from wet filters and dry filters of full-scale groundwater treatment plants indicate that, in wet filters, adsorptive iron removal also plays a role. In dry filters, this mechanism should be dominant due to a very short pre-oxidation time. Process efficiencies of wet filters with iron oxide coated sand can be further improved by operating the filters predominantly in the adsorptive filtration mode.
Change of bacterial water quality in drinking water distribution systems working with or without low chlorine residual
Authors: Wricke B. , Korth A. , Petzoldt H. , Krüger M.
Published: May 2018

Investigations into distribution systems (DS) working without or with low disinfectant residuals showed that the main process for the bacteria change in such systems is the release of bacteria from the biofilm, whereas the growth of bacteria in the water can be neglected. Important for the quality are short-term increases of bacteria release connected to an increase of bacteria growth on the inner pipe surface as a result of changes in the concentration of biodegradable organic matter (BOM) in the water. A model to describe the bacterial water quality change was developed on the basis of investigations. In contrast to other models, a consideration of the formation of BOM as a result of NOM oxidation by disinfectant residuals as well as the decreasing effect of inactivation of released bacteria by the decreasing disinfectant residual concentration, were necessary.
Substrate turnover at low carbon concentrations in a model drinking water distribution system
Authors: Boe-Hansen R. , Albrechtsen H.-J. , Arvin E. , Jørgensen C.
Published: May 2018

Water quality changes caused by microbial activity in the distribution network can cause serious problems. Reducing the amount of microbial available substrate may be an effective way to control bacterial aftergrowth. The purpose of the present study was to study the kinetics of substrate utilisation and bacterial growth at low nutrient conditions in a model distribution system. The model system consisted of two loops in series, where flow rate and retention time were controlled independently. Spiking the drinking water of the model system with two different environmentally realistic concentrations of carbon allowed for a close monitoring of the kinetics of substrate turnover (less than 10 μmg C/L 14C-benzoic acid was added). The mineralisation of benzoic acid was rapid and could be modelled by a no-growth Monod expression using a maximum degradation rate of 0.59 μmg C/L/h and a half-saturation constant of 2.6 μmg C/L. Only 2-4% of the carbon being degraded was incorporated into the biofilm. The results from our study suggest that the cell-specific respiration of biofilm was much higher than for suspended bacteria, and that the growth rate of the bulk phase bacteria was approximately 10 times higher than the biofilm bacteria.
Controlled treatment with nitrate in sewers to prevent concrete corrosion
Authors: Æsøy A. , Østerhus S.W. , Bentzen G.
Published: May 2018

It has generally been accepted that concrete corrosion is caused by bacterial oxidation of hydrogen sulphide in sewage systems. Costs related to sewer replacement and remediation are quite high, but there is limited knowledge and documentation on the relationship between hydrogen sulphide levels and corrosion rates. This is necessary information in order to select the appropriate means of hydrogen sulphide control and to conduct cost-benefit evaluations. This pilot scale study shows that the concrete corrosion rate can be modeled by a Monod type function with Ks=2 ppm H2S in gas and a maximum concrete corrosion rate at 25°C of 16 mm/year. Complete hydrogen sulphide control with 0 ppm H2S in water and gas is required to prevent concrete corrosion. This can be achieved by controlled treatment with nitrate using the Nutriox® Concept where the nitrate dose is based on flow, temperature, sewer design, and sewage concentration. The local conditions will be important for the cost-benefit evaluations, but in general terms, one can say that the longer the hydraulic retention time is, the more cost effective will a controlled treatment with nitrate be for corrosion control.
Use of recycled crushed glass as a filtration medium in municipal potable water treatment plants
Authors: Evans G. , Dennis P. , Cousins M. , Campbell R.
Published: May 2018

The aim of this study was to investigate the use of recycled crushed glass as a filtration medium for municipal potable water treatment plants. It evaluated the main physical parameters of recycled glass and its performance in a potable water treatment application. Pilot-plant testing was used to compare the performance of recycled glass to a typical sand filter medium in a conventional treatment process. Laboratory analysis was used to determine media characteristics. Pilot-plant testing determined that the filtration performance of the glass medium was similar to that of a typical sand medium of similar effective size and uniformity under all conditions tested. The glass medium had the benefit of taking 10-15% longer than the sand to reach particle breakthrough. The glass also appeared to accumulate headloss in most runs at a slightly lower rate than the sand. Backwashing observed during pilot-plant testing also showed that the glass expanded more than the sand under the same backwash water rates. This was noted to be a potential benefit to installations that have low backwash water flow.
Preliminary investigation of electrocoagulation as a substitute for chemical coagulation
Authors: Han M. , Song J. , Kwon A.
Published: May 2018

Recently electrocoagulation has been considered as one of the promising coagulation processes and was increasingly used as a substitute for chemical coagulation in many water treatment fields. However, there have not been many fundamental studies performed on it. In this research, a preliminary investigation was carried out to verify the effectiveness of the electrocoagulation compared with conventional chemical coagulation through a set of batch experiments. Turbidity removal efficiencies, using various aluminium dosages and at different water pH values, were investigated. In addition, the zeta potential was studied to develop understanding of particle characteristic after applying both electrocoagulation and chemical coagulation. It can be concluded from the results that electrocoagulation is more efficient than chemical coagulation in turbidity removal.
Coagulation of turbid waters using Moringa oleifera seeds from two distinct sources
Authors: Narasiah K.S. , Vogel A. , Kramadhati N.N.
Published: May 2018

Samples of turbid water prepared under laboratory controlled conditions were tested using natural coagulant-flocculant Moringa oleifera seeds from Burundi, Central Africa, and from Mahajanga, Madagascar. Coagulation-flocculation and sedimentation experiments were conducted using jar test equipment. For these tests, 5% Moringa oleifera solutions (w/w in water) were prepared using shelled and non-shelled seeds from the aforementioned countries. The results show that, in both cases, the shelled seeds provide much higher turbidity removal than the non-shelled ones. In addition, the volume of sludge produced was approximately 30% of that of conventional coagulants such as alum. Finally, it was concluded that seeds from Burundi were of superior quality than those of Madagascar. In fact, higher dosages of these seeds, of up to four times, were required in order to attain the same level of turbidity as the Burundi seeds.
Properties of flocs formed using different coagulants
Authors: Yukselen M.A. , Gregory J.
Published: May 2018

The effects of shear on the formation and break-up of flocs generated using aluminium sulphate (“alum”), polyaluminium chloride and a cationic polyelectrolyte have been investigated using conventional jar test procedure and by continuous optical monitoring. Using the experimentally determined optimum dosage, the breakage of flocs was followed at a high stirring speed, corresponding to average shear rate (G) of about 330-520 s-1. Most of the breakage occurred within a few seconds of increasing the shear rate. After each breakage the stirring rate was reduced to the original value to allow the flocs to re-grow. For alum and polyaluminium chloride, it was found that only limited re-growth of flocs occurred indicating a significant irreversibility of the floc break-up process. Residual turbidity increased after floc breakage and re-growth, indicating a reduction in sedimentation rate of the re-grown flocs, consistent with the continuous monitoring results. For the cationic polyelectrolyte, the re-growth of flocs occurred to a much greater extent and floc breakage was almost fully reversible.
A comparison of conventional and non-conventional treatment technologies on arsenic removal from water
Authors: Ngo H.H. , Vigneswaran S. , Hu J.Y. , Thirunavukkarasu O. , Viraraghavan T.
Published: May 2018

In this study, four treatment methods were used to remove arsenic from water, namely: (i) chemical precipitation, (ii) arsenic adsorption onto iron-oxide-coated sand, (iii) high-rate saturated floating-medium flocculator/filter and (iv) membrane hybrid system (adsorption-microfiltration). The results indicated that more than 90% of total arsenic was removed by using FeCl3 (40 mg/L) as coagulant. The removal efficiency was 10% lower when polysilicato-iron (PSI, 2.5 mg/L) was used as a flocculant. The results of both the batch and column adsorption studies showed that iron-oxide-coated sand can effectively be used to achieve very high levels of arsenic removal (less than 5 μm/L as As in drinking water). Arsenic was removed up to 78% from the packed polystyrene beads filter with in-line FeCl3 addition at a high loading rate of 30 m3/m2.h. When powder activated carbon (PAC) was used in the membrane hybrid system, 87% removal of arsenic was achieved. A mixing time of 2.7 min with the mixing intensity of 87.8 s-1 were used. A very high filtration (permeate flux of 760 L/m2.h) was observed with a membrane of pore size of 0.2 μm.
Treatment options for the saxitoxin class of cyanotoxins
Authors: Newcombe G. , Nicholson B.
Published: May 2018

The saxitoxin class of algal toxins (cyanotoxins) are neurotoxins produced in Australia by the blue-green alga (cyanobacterium) Anabaena circinalis. A range of water treatment processes was investigated for the removal of these compounds. Ozonation of the toxins at moderate doses was found to be ineffective. Chlorination was found to be effective at high pH; therefore where pH adjustment is possible in the treatment process, chlorination could be considered as an important treatment option. Activated carbon, both in the granular and powdered form, was effective for reducing the toxicity of a mixture of the toxins as the most toxic of the saxitoxins were also the most readily removed by adsorption.
Natural organic matter removal by enhanced photo-oxidation using low pressure mercury vapour lamps
Authors: Thomson J. , Roddick F. , Drikas M.
Published: May 2018

High efficiency, low pressure mercury vapour lamps producing radiation at the wavelengths of 254 plus 185 nm and 254 nm only, were used to investigate the H2O2 enhanced photo-oxidation of natural organic matter (NOM). NOM is a problem in drinking water for a number of reasons: aesthetics; it provides an energy source for the growth of microorganisms in the distribution system; and reacts with chlorine to produce potentially harmful disinfection by-products. One promising oxidant for the removal of NOM from drinking water is the hydroxyl radical. The aim of this work was to investigate the kinetics, mechanisms, and feasibility of treatment of a highly coloured natural water by H2O2 enhanced UV (254 nm alone or with 185 nm). Kinetic models were applied to the data as a tool to understand the mechanisms and give a basis for process scale-up. Electrical energy per order criteria were used to determine the most efficient process. Irradiation by 254 plus 185 nm was found to be more efficient than 254 nm alone for low H2O2 doses, although at higher doses the performance of the two systems became similar. Size exclusion chromatography revealed three distinct fragmentation patterns for the different processes.
Facing water shortage in a Mediterranean tourist area: seawater desalination or water reuse?
Authors: Xu P. , Brissaud F. , Salgot M.
Published: May 2018

An integrated technical-economic modelling framework was developed to help planning and managing of water resources in a Mediterranean tourist area, Palma on Majorca island (Spain). Due to high water demand, groundwater resources are depleted and new water resources should be developed. Seawater desalination has become an important solution to water shortage, especially in the summer tourist season. Meanwhile, reclaimed water has been applied for agricultural and landscape irrigation. With regard to the treated wastewater not being effectively reused, further water reuse scenarios are envisaged in order to meet new water demand, restore over-exploited aquifers and reduce expensive seawater desalination. Three types of models were established and coupled: (i) hydrological models; (ii) water demand and/or need model; (iii) technical-economic model. In addition, a multi-criteria analysis completed the technical-economic modelling. The simulated water reuse scenarios are not alternative but complementary. They provide the possibilities for total reuse of wastewater in the Palma area. Compared with seawater desalination, water reuse is a cost-effective solution to address water scarcity issues in the Palma area. Using tertiary effluent for landscape irrigation allows over-exploited aquifers to recover. It is very attractive in terms of economic benefits and feasible with respect to technical and social aspects. Further water reuse for extending agricultural irrigation can greatly reduce seawater desalination but acquiring the farmers' agreement to give up pumping groundwater for irrigation would meet some difficulties. Water recharge would help to totally reuse wastewater but uncertainties related to public perception and the attitude or regulatory board and local authorities need dealing with. Because water reuse requires a long-term managing viewpoint in order to prepare and demonstrate its feasibility and security, seawater desalination was adopted as an emergency solution to meet peak demands during the tourist season and in case of drought.