bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of irrigation on poverty: a framework for analysis
Authors: Lipton Michael , Litchfield Julie , Faurès Jean-Marc
Published: May 2018

Irrigation projects have been the subject of much bad press coverage because of the sometimes very damaging environmental and social impacts associated with large-scale projects such as dams, declining aid to agriculture and falling rates of economic returns to irrigation since the heyday of the 1970s. Yet irrigation remains one of the most crucial inputs into farming and therefore a potentially important poverty reduction tool for the 21st century. We review some of the evidence surrounding trends in investments in irrigation and the reasons behind the decline. We also provide a framework for analysing the positive and negative impacts of irrigation on poverty, how these might differ by the type of irrigation technology and review some of the evidence of these impacts. We reach a number of conclusions about the conditions under which irrigation is most likely to have a positive impact on the poor, but we also report that the evidence is patchy, and usually not gathered in such a way as to allow easy conclusions to be drawn.
Water, poverty and gender: review of evidences from Nepal, India and South Africa
Authors: Upadhyay Bhawana
Published: May 2018

Access to water in equitable manner and the improved management of water are imperative to sustainable development, poverty alleviation and biodiversity preservation. Despite much research on gender and natural resources management, there have been only a handful of studies on gender and water, especially those trying to link the two with poverty issues. This paper seeks to fill this gap specifically by looking at the linkages among gender, water and poverty in terms of gender participation in irrigated agriculture and irrigation institutions. The main objective of the study is to examine gender participation in irrigated agriculture and irrigation institutions and to analyze the impact of irrigation projects on men and women. The study approach has been a qualitative and quantitative analysis of primary and secondary data.

Key findings reveal a considerable degree of gender inequalities, especially in terms of participation in irrigation institutions. Despite a high level of female involvement in irrigated agriculture, their participation in irrigation institutions is much lower. Furthermore, water projects with gender equality interventions have enhanced women's status in particular by raising their abilities to participate. The results suggest that the incorporation of gendersensitive policies and programs in irrigation schemes could have significant positive impacts both on gender equality and poverty.
A nationwide assessment of wastewater use in Pakistan: an obscure activity or a vitally important one?
Authors: Ensink Jeroen H.J. , Mahmood Tariq , van der Hoek Wim , Raschid-Sally Liqa , Amerasinghe Felix P.
Published: May 2018

A nationwide assessment in Pakistan showed that the direct use of untreated wastewater for agriculture, particularly vegetable production, was common in most cities. The main reasons for this use were the absence of alternative water sources, the reliability of the wastewater supply, the nutrient value and the proximity to urban markets. It was estimated that 26% of the total domestic vegetable production of Pakistan was cultivated with wastewater. The importance of the wastewater was re.ected in high water and land fees. Policy makers have to take the importance for local livelihoods and food security into account when making decisions regarding direct wastewater use.
Implications of the World Bank's privatization policy for South Africa
Authors: Jones Sharon A. , Duncanson Catriona Mhairi
Published: May 2018

Providing potable water is a central issue for all nations and is of particular concern in developing countries where universal coverage does not exist. This paper evaluates the implications of the World Bank's privatization policy for the water sector in developing countries using South Africa as an example. The authors conclude that regardless of private investment, cost-accounting reform is needed both to provide universal services and to practice environmental stewardship. Based on theory and empirical evidence, concessions appear to be the optimal form of water sector privatization. The structure of the water sector in South Africa favors the use of concessions if a privatization strategy is pursued. The South African case shows that the success of attempts to privatize a monopolistic water sector depends on developing adequate regulatory and administrative capacity. This conclusion aligns closely with the current World Bank privatization policy. However, the authors argue that the Bank policy does not explicitly address several issues that are necessary to maximize the benefits of privatization. In addition, the authors agree with other analysts who suggest that the World Bank would benefit from a new paradigm for infrastructure privatization that is more transparent and includes a coalition of stakeholders with community involvement.
Trading virtual water between Bangladesh and India: a politico-economic dilemma
Authors: Parveen Saila , Faisal I. M.
Published: May 2018

The extent of virtual water trade and its significance for the food security of Bangladesh have been examined in the light of political and socio-economic considerations that govern the food grain trade between Bangladesh and India. It has been shown that while there are no physical constraints preventing such a trade, prevailing political relations, market conditions, agricultural and food policies, the state of the economies and climatic conditions may play important roles in determining the extent of trade. In the context of rapid population growth and potential future shortage of cultivable land and irrigation water in the dry season, the paper suggests that food security may be redefined as “food self-reliance” instead of “food self-sufficiency”.
Water institutional reforms in South Africa
Authors: Backeberg Gerhard R.
Published: May 2018

A comprehensive program of water institutional reforms has been implemented in South Africa since 1994. These reforms followed some major reform on the political and economic fronts. The institutional changes that occurred in the water sector covered the policy legal, and organizational dimensions of water allocation and management and affected all water sub-sectors including environmental allocations. The reform process has culminated in a new national water policy, a national water act and a national water resources strategy. Substantial organizational changes have also occurred with a focus on management decentralization, user participation and license-based allocation of water. This paper aims to provide an overview of these and other changes, especially from the perspective of irrigation and agriculture. It also attempts to explain the emergence and implementation of the water institutional reforms process in the light of the results reported in recent literature on water institutional reforms. The paper provides evidence for the role of transaction cost and political economy considerations as well as the use of reform design and implementation principles such as institutional sequencing and reform timing.
Water institutional reforms in Sri Lanka
Authors: Samad Madar
Published: May 2018

This paper reviews water institutional reforms in Sri Lanka by contrasting those observed during the 1980s with those proposed during the 1990s. While the earlier reforms focused on the irrigation sector that yielded quicker benefits and low political risks, recent reforms have covered macro institutions and the whole water sector where the benefits are gradual and less visible but with high political risks. As the earlier reforms were packaged as part of larger investment programs, they had in-built incentives and strong proponents. But recent reforms not only lacked such conditions but also faced an ideologically charged hostile environment. Despite the current failure of the reforms, their future prospect is not that bleak in view of the emerging consensus on most issues and the continuing government commitment to reform. The Sri Lankan case also provides evidence for the effects of transaction cost and political economy factors, the tactical benefits of reform packaging, sequencing and timing, and the role of stakeholders' perception, learning and information in articulating the demand for change.
Water tariffs in Lebanon: a review and perspective
Authors: Chatila Jean G.
Published: May 2018

Lebanon is increasingly suffering from shortage and mismanagement of water, which is becoming a commodity of considerable value owing to the inadequacy of supply to meet the needs of potential users. Water authorities and establishments fix tariffs that users have to pay to obtain water. In fact, these tariffs should represent the total costs of providing good quality water in adequate quantities. However, currently domestic water tariffs in Lebanon are mostly flat and not enough to cover the salaries of the employees and the charges of minor maintenance works. Domestic water is sold at a nominal daily flow where rates are lower for smaller towns and increase proportionally. In addition, not all subscribers are actually paying their dues and the water authorities are unable to control and limit illegal connections. As for irrigation practices, water is generally priced at a flat rate or at rates that are associated with the area that the users are allowed to invest in. This paper describes the different aspects of the water tariff structures in Lebanon, provides a review of the current water tariffs available for the different sectors and presents recommendations and ideas for a new water tariff system in the newly formed water authorities.
Agricultural groundwater use in sub-Saharan Africa: What do we know and where should we go?
Authors: Giordano Mark
Published: May 2018

Relatively little is known about agricultural groundwater use and the agricultural groundwater economy of sub-Saharan Africa. However, available evidence suggests that the region's groundwater resources are substantial and greater in per capita terms than in some of the worlds' largest agricultural groundwater users including India and China. Nonetheless, calculations presented here also indicate that the direct contribution of groundwater to sub-Saharan Africa's agricultural economy is small, both in absolute and relative terms. Plausible explanations for low usage include physical geography, economics and economic policies, and politics. In addition to these real factors, incomplete information almost certainly contributes to an underestimation of agricultural groundwater use. Further, it is likely that “traditional” approaches to groundwater valuation inherently miss some of the key groundwater functions in the sub-Saharan African context, in particular as they relate to livestock production and rainfall variability. While this paper supplies a baseline of information in some respects, much additional research is needed to improve our basic understanding of sub-Saharan Africa's agricultural groundwater use and importance, not only to help researchers and policy makers appreciate the value of the region's groundwater resources but also to provide a meaningful knowledge base on which development plans can be built. That said, the ultimate point of applied research should be to understand both where additional development in sub-Saharan Africa is possible and, equally important, where and why it is not.
The viability of decentralized water and sanitation provision in developing countries: the case of Honduras
Authors: Pearce-Oroz Glenn
Published: May 2018

The sustainable delivery of basic services continues to be an elusive goal for water and sanitation operators in developing countries. In Honduras, both centralized and decentralized providers of water and sanitation coexist simultaneously, providing an opportunity to compare the effectiveness of each approach amid similar constraints. This analysis uses ten variables that measure access, efficiency and sustainability, in comparing the experiences of 16 potable water systems in small- and medium-sized cities, operated by centralized and decentralized water authorities. While neither approach provides a single, integrated model of a best practice, overall the decentralized systems demonstrate better practices than their centralized counterparts. Decentralized potable water systems systematically outperform centralized ones in financial efficiency and in their ability to increase coverage of basic services over time. In large part, the decentralized systems' better practices have been motivated by institutional arrangements that promote political accountability to customers and provide incentives for sustainable management practices. Decentralized operators continue to face challenges, namely the need to apply economic principles in designing tariff regimes and implementing management practices to account for capital depreciation. Despite these challenges, however, this analysis demonstrates that decentralized systems are not only viable in developing countries, but also tend to provide better service than those systems operated by a centralized authority.
Economic incentives encourage farmers to improve water management in California
Authors: Wichelns Dennis
Published: May 2018

Economic incentives are used in many situations to motivate improvements in the use of scarce resources. In some areas, implementing appropriate incentives is made challenging by the nature of existing institutions or the inability to assign property rights and measure individual use of key resources. Higher prices for irrigation water can motivate wiser use of water in regions where the opportunity cost of water is rising, due to increasing municipal, industrial and environmental demands. This paper describes how an increasing block-rate pricing structure was designed and implemented in an irrigation district in central California. The goals of the program were to improve water management practices and reduce the volume of subsurface drain water discharged into the San Joaquin River. Results describing reductions in average irrigation depths and drain water volumes, collected throughout the 1990s, demonstrate the potential for achieving resource management goals with economic incentives that motivate changes in farm-level management practices. Complementary incentive programs and issues regarding program implementation and the sustainability of drain water reduction efforts in an arid region also are discussed.
Invited Opinion PieceThe Young People's Declaration: will they be heard?
Authors: Kabakian Vahakn
Published: May 2018

Water related issues have been debated and discussed over the past two decades and still there is no resolution. After almost 3 years from the Second World Water Forum, where participation and social involvement were put high, arguments on who should govern and finance water services prevailed at the 3rd WWF. Worrying about the “situation” of water, young people gathered at the Second Youth World Water Forum (2nd YWWF) during the 3rd WWF formulated the Young People's Declaration. This article illustrates the Young People's Declaration and questions whether or not their demands would be met.
The control of cyanobacterial blooms by plant growth retardants (ancymidol, paclobutrazol, uniconazole)
Authors: Romanowska-Duda Z. , Tarczyńska M. , Zalewski M.
Published: May 2018

The seasonal blooming of cyanobacteria in water bodies creates considerable medical and veterinary problems, because certain species are potential sources of toxins, principally neuro- and hepatotoxins. Much effort has been devoted to prevent them blooming. In this study, axenic cultures of Microcystis aeruginosa and Anabaena sp. were cultivated in medium Z supplemented with growth retardants. Cells were counted under a microscope each week for up to 8 weeks of culture. The growth retardants paclobutrazol, ancymidol and uniconazole greatly reduced the number of living cells, the effect already being striking after 24 hours of culture. Plant growth retardants can be effectively used in control of cyanobacterial blooms.
Copper corrosion control in the Netherlands
Authors: Slaats P.G.G. , Brink H. , van der Hoven T.J.J.
Published: May 2018

Copper is the most commonly used material for pipes in domestic installations in the Netherlands. Depending on the composition of the water the copper pipes can add a significant amount of copper to drinking water. In the new European Drinking Water Directive (98/83/EC) the parametric value for copper in drinking water is decreased from 3 to 2 mg/l. The new directive also stipulates that copper levels should be determined on the basis of a sample ‘taken at the consumers' tap’ representative of the weekly average intake by humans. Harmonisation of monitoring protocols for copper in the European member states is necessary.

In the Netherlands about 45% of the drinking water is already softened or de-acidified in order to decrease copper concentrations in drinking water. In the Netherlands two new treatment techniques have been studied for their impact on copper release; these are Reverse Osmosis (RO) and the addition of inhibitors.

Copper pipe rig tests have shown that RO treatment decreases copper release. Split treatment of water with RO reduces copper solubility of drinking water through a decrease in both total inorganic carbon (TIC) and sulphate level. Remarkable was the relatively small decrease in copper release after split treatment with RO, compared to previous experiences in the Netherlands, suggesting an effect of natural organic matter. A new promising technique in the Netherlands is the addition of the inhibitor carbonate-activated silicate. At the test sites, the reduction in copper solubility due to the use of carbonate-activated silicate was 15 to 35%.
Use of a mass balance model for developing guidelines for treatment plant recycle streams
Authors: Carlson K.H. , Bellamy W.H.
Published: May 2018

Recycling treatment, plant waste streams has become an important issue and the EPA is currently developing a rule for controlling and potentially limiting these streams. The impact to the overall treatment process and the relative risk of various recycle streams can be evaluated with a materials balance model of a treatment plant. A steady-state materials balance model was developed and applied to the recycle of backwash waste water, clarifier sludge supernatant and sludge dewatering supernatant. Recycling backwash water reduced the plant treatment effectiveness from 3.0 log to 2.95 log removal when the recycle stream was treated (0.5 log removal) and 2.84 log removal when not treated. Recycling clarifier sludge supernatant resulted in a reduction of performance from 3.0 log to 2.78 log removal with adequate treatment (0.5 log removal) and 1.95 log removal with inadequate treatment (10% removal). The model was used to identify vulnerable treatment conditions. Conventional treatment with a poorly operated or upset clarifier was identified as a significant risk with the overall treatment effectiveness decreasing from 3.0 to 2.3 log removal.
Hypolimnetic oxygenation: predicting performance using a discrete-bubble model
Authors: Little J.C. , McGinnis D.F.
Published: May 2018

Stratification of water-supply reservoirs frequently results in substantial hypolimnetic oxygen depletion with a resulting negative impact on raw water quality. Hypolimnetic oxygenators are used to add oxygen to the hypolimnion without significantly disrupting the thermal density structure. The three most common devices are the airlift aerator, the Speece Cone, and the bubble-plume diffuser. A discrete-bubble model based on fundamental principles has previously been shown to hold considerable promise for predicting the performance of airlift aerators and the Speece Cone. In this paper, we have further verified this model by comparing its predictions to a series of pilot-scale experimental measurements and have also demonstrated its ability, under somewhat idealized conditions, to predict the full-scale performance of a bubble-plume diffuser in a stratified reservoir. The potential for the diffused-bubble aeration system to increase oxygen demand, and the rate at which nitrogen builds up during operation and de-gasses following destratification, are also considered.
Sustainable urban water - analysis of the opportunities
Authors: Speers A. , Booker N. , Burn S. , Gray S. , Priestly T. , Zoppou C.
Published: May 2018

This paper describes a major program of research by the Commonwealth Scientific and Industrial Research Organization (CSIRO) into urban water, wastewater and stormwater services. The intent of the program has been to identify opportunities for achieving more sustainable urban water services. The term “sustainable” has been interpreted to mean improvements in environmental and economic performance of systems which maintain inter- and intragenerational equity. It is evident from the conclusions of the feasibility stage of the Urban Water Program that such opportunities exist, particularly with regard to the design and configuration of water and wastewater systems. The structure of the UWP is described and examples of critical outcomes given.
Ultrafiltration membrane full-scale experience: status after 10 years of operation and large-scale plant capacity 100,000 m3/day
Authors: Laîne J.-M. , Durand-Bourlier L. , Vial D.
Published: May 2018

UF has been found to exceed all current and anticipated future disinfection regulations regardless of the variations in resource quality. Thus, the application of UF technology has expanded considerably for drinking water treatment. Capital costs decreased by a factor of about 2.5 between 1989 and 1994. The standardization of the plants and the increase of membrane surface area per module allowed a lower manufacturing cost and therefore a higher production volume of the UF membrane modules. The optimized technology is now competitive as compared to conventional processes even for large scale plant capacities of 65,000 m3/day. The paper provides an overall overview on the UF process based on actual operating data from an O and M and capital cost perspective, but also tries to provide responses from an operator perspective by analysing long-term membrane process performances, including chemical cleaning requirements and membrane replacement frequency.
Competitive removal of VOCs with GAC and BAC following advanced oxidation processes
Authors: Lee S.H. , Kim Y.R. , Yu M.J.
Published: May 2018

Studies have been conducted to remove trichloroethylene (TCE), tetrachloroethylene (PCE) and 1,1,1-trichloroethane (1,1,1-TCA, TCA) as volatile organic compounds (VOCs) using the combination of chemical oxidation, adsorption by granular activated carbon (GAC) and biological activated carbon (BAC) with a selected microbial consortium (SMC). The purposes of this research were to investigate the competitive removal of VOCs and to develop the most optimal process by using a pilot plant composed of three GAC columns and three BAC columns. Simulated groundwater systems were used not only to examine the competitive adsorption availability for VOCs on GAC and BAC but also to examine the oxidation efficiency using O3 alone and H2O2/O3. The microbial species isolated from the soil contaminated by VOCs were Gram-negative, rod-shaped bacteria, identified as Pseudomonas aeruginosa, Pseudomonas maltophilia, Acinobacter calcoaceticus and Bacillus sphacricus. The results revealed that systems pre-treated by H2O2/O3 were more effective at removing VOCs than systems treated by ozone alone and non-pre-treated systems. The mixture of VOCs was removed in the order of PCE, TCE and TCA in GAC and BAC systems. Biological treatment alone was not effective at removing VOCs. However, pre-treatment of these chemicals by H2O2/O3 showed high removals. PCE and TCA were less effective than TCE at being oxidized by chemical oxidation and biodegradation.
Removal of natural organic matter (NOM) using ozonation and ultrafiltration
Authors: Chang T.-C. , Pan Y.-W. , Chen S.-S. , Chen C.-K.
Published: May 2018

Pilot studies were conducted at Liu-Du water treatment located in Keelung, Taiwan. Raw water was first treated by conventional coagulation- sedimentation-filtration (CSF) processes, and then pumped into the pilot plants. For the pilot plants, both ozone/GAC and ozone/UF processes were operated simultaneously for NOM removal comparisons. Both systems were controlled at the same operating conditions with ozone dosing of 4.5, 6.0 and 9.0 mg/L. The results demonstrate that both ozone/UF and ozone/GAC processes can enhance NOM removal after the CSF process. More NOM was removed by the Ozone/GAC process because ozone broke the large molecules into smaller molecules, which increases the GAC adsorption potential. However, the ozone/UF process provides higher removal capacity in turbidity. In both processes, ozone dosing was not proportional to NOM removal of each process and 6.0 mg/L is found to be the optimal dosing. Owing to increasing adsorbability by ozonation, the ozone/GAC process is a very competitive process in NOM removal when associated with the CSF process.
Membrane filtration of surface water in the presence of ozone
Authors: Sawada S. , Sumida I. , Matsumoto K.
Published: May 2018

The preliminary study investigated the effect of pre-ozonation of synthetic raw water (bentonite and humic acid) on membrane fouling. The results showed that humic acid, not bentonite, was the dominant factor in membrane fouling. When the synthetic raw water was pre-treated using ozone and activated carbon, stable operation was possible at twice the flux of membrane filtration without pre-treatment. Thus, ozone and activated carbon reduced the concentration of organic matter (humic acid), leading to an increase in flux.

Secondly, an MF membrane filtration device with ozone tolerance was attached downstream of the ozone reactor so that residual ozone could reach the membrane surface. When water was treated with MF membrane filtration in the presence of ozone, the flux was stable at 4 m/d. The membrane filtration resistance increased when ozone was not injected, and decreased when it was injected. This phenomenon was repeatable. In the presence of ozone, organic matter that could accelerate fouling as decomposed and converted to less fouled materials, resulting in a suppression of fouling as well as facilitating removal of the fouling layer during back washing.
Using a membrane bioreactor/reverse osmosis system for indirect potable reuse
Authors: Lozier J. , Fernandez A.
Published: May 2018

The City of McAllen, Texas, with the assistance of CH2M HILL, has pilot tested an integrated membrane bioreactor (MBR)/reverse osmosis (RO) treatment train to reclaim municipal wastewater to a quality suitable for use as a new drinking water supply in the process called indirect potable reuse. Previous testing by the City (Phase 1) demonstrated the applicability and cost of microfiltration (Memcor and ZeeWeed systems) to enhance the quality of secondary effluent for subsequent treatment by RO and the feasibility of a membrane bioreactor system (ZenoGem) to produce RO feedwater directly from minimally processed sewage. Phase 2 testing, reported on in this paper, is designed to demonstrate reliable operation of MBR/RO treatment for processing screened, degritted sewage and that the effluent from such a train can meet all federal primary and State secondary drinking water regulations and comply with anticipated State requirements for indirect potable reuse. Results show the ZenoGem process to be reliable, require minimal operator attention and maintenance, produce an effluent that can be processed by RO with little fouling and that easily exceeds the City's current effluent discharge requirements relative to BOD, TSS and ammonia. The ZenoGem permeate quality exceeds RO feedwater criteria for turbidity and silt density index and RO system performance confirms minimal membrane fouling by particles. However, the high calcium hardness and phosphate levels in the City's wastewater (and ZenoGem permeate) caused mineral precipitation within the RO system when operated at higher recoveries. Precipitation can be controlled, however, by increased acidification of the RO feedwater.
Performance comparison of direct membrane separation and membrane bioreactor for domestic wastewater treatment and water reuse
Authors: Ahn K.-H. , Song K.-G. , Yeom I.-T. , Park K.-Y.
Published: May 2018

Two pilot-scale wastewater treatment systems - direct membrane separation (DMS) and membrane bioreactor (MBR) systems - were designed and constructed in order to investigate the feasibility of membrane filtration technology for domestic wastewater treatment and water reuse. A submerged-type hollow-fiber microfiltration (HF-MF) membrane module with pore size of 0.1μm was employed to build each pilot system. The systems were tested using low- and high-strength domestic wastewaters and the system performance was continuously monitored for a long period to compare filtration characteristics and effluent quality in each system. The MBR system showed much better performance than the DMS system in terms of filtration characteristics and effluent quality. Even though the mixed-liquor suspended solid (MLSS) content in the MBR system was much higher than that in the DMS system, the MBR filtration resistance was much lower than the DMS filtration resistance. The DMS system was not able to remove dissolved organic matter, which seemed to be a major component of membrane fouling. The MBR effluent quality such as COD, BOD, TOC and T-N was more stable and better than the DMS. In the MBR process, the organic removal efficiency remained more than 95% regardless of fluctuation in influent qualities. The effluent quality of both systems was satisfying the legal standards for water reuse in Korea. Rejection of pathogenic microorganisms by membrane filtration was also investigated.
Pretreatment processes for membrane filtration of raw water containing manganese
Authors: Takizawa S. , Fu L. , Pradhan N. , Ike T. , Ohtaki M. , Ohgaki S.
Published: May 2018

Experimental studies on chemical and biological pretreatments in membrane filtration processes were carried out to removal manganese contained in raw water and to prevent membrane fouling due to manganese. Two types of the pretreatment reactors, i.e. the fluidised-bed and fixed-bed configurations, were compared in the biological pretreatment experiments. New synthetic media (tubular polypropylene, I.D. 3 mm, O.D. 4 mm, length 5 mm) were used in all three experiments as a manganese-oxidising catalyst. The chemical pretreatment using sodium hypochlorite was effective in manganese removal and controlling membrane fouling; more than 0.8 mg-Cl2/L of chlorine dose was necessary to bring the manganese concentration from 0.4 mg/L in raw water to less than 0.05 mg/L. The biological pretreatment for manganese removal required a long start-up period of more than 40 days. The fixed-bed biological pretreatment was superior in manganese removal and in control of membrane fouling to the fluidised-bed biological pretreatment, which showed wash-out of the attached bacteria resulting in membrane fouling. The linear velocity and the empty-bed retention time required for the treatment of 0.14 mg-Mn/L in the fixed-bed biological pretreatment was 206 m/d and 8.0 minutes, respectively.
Process water treatment and recovery of product from the refinement of inorganic basic chemicals by means of membrane filtration
Authors: Baumgarten G. , Wortel A.
Published: May 2018

A chemical factory has been given the instruction from the government environmental agency that the process wastewater from the production of inorganic base chemicals must be free of individual contaminants before discharge into the sea. Since the filtration and sedimentation of these solid materials established up until now could not be performed guaranteed, suitable treatments had to be connected downstream. Amafilter has developed and built a specially designed membrane process in two production lines for four waste water streams through which the product loss is reduced to a minimum and the permeate can be reused. The plants have now been running successfully since April 1999.
The new concept of flux enhancement during cell separation with MF/UF processes
Authors: Kołtuniewicz A.
Published: May 2018

The microfiltration and ultrafiltration processes are considered as matured membrane processes that are well established in industrial practice. Nevertheless, the main obstacles of their further development in the new competitive implementations are the economical problems. The key economic factors are permeate flux and energy consumption. However, although the cross-flow systems enable us to attain higher flux, it is usually very expensive. The high energy is consumed to maintain circulation velocity of the retentate that is sufficient for sweeping out the retained component from the membrane surface. Moreover in the case of cells separation the high intensity of the fouling and low cake permeability makes it necessary to apply additional efforts, such as backflushing, backpulsing, promoters of turbulence, vibrations, ultrasounds and many other. Therefore, dead-end systems are still quite competitive with cross-flow, especially for diluted (less than 0.5% of dry mass) suspensions or solutions.

Cell separation with membranes is one of the most vivid problems for modern biotechnology, wastewater and water treatment. Membranes offer mild process conditions and high selectivity of separation. This enables us to solve a variety of problems such as cell culturing, fractionation, concentration, purification and sterilisation. The selected cells may be precisely separated from other components of broth and subsequently directed into the reaction space again in good conditions to ensure a quasi-continuous mode of operation. Moreover, membranes enable us to attain high efficiency of the bioconversion by removal of all product and inhibitors directly from the bioreactor. This is the reason for the huge interest in cell separation with membranes.

The idea of the paper was to present the new concept of flux enhancement for cell separation on membranes. This concept lies in taking advantage of the specific rheological nature of biopolymers, which are the main foulants. The biopolymers retained on the membrane surface (i.e. on the top layer) can be applied as a lubricant for the cells that can settle on such a ‘movable layer’. As is shown, further in the paper, the thickness of the moving layer is lower and the flux is greater. The common movement of the cells and gel layer is very convenient from the cells integrity point of view. However the hydrodynamic conditions always play an important role in cross-flow systems; the resistance of ultrafiltration membranes may be reduced much more when compared with more open microfiltration membranes.
Aerated biological filtration for the removal of ammonia and manganese in a major new water treatment works under construction in Hong Kong
Authors: Heard T.R. , Hoyle B.G. , Hieatt M.J.
Published: May 2018

Construction is currently under way in Hong Kong of a US$ 575 million water treatment and transfer scheme including the first 250 Ml/d stage of a new water treatment works at Tai Po, with an ultimate capacity of 1,200 Ml/d. The design incorporates primary aerated biological filters for ammonia and manganese removal as a key element of the treatment strategy.

Pilot filter work was carried out for a period of over twelve months covering seasonal variations. The work included investigations into “start up” times; ammonia removal efficiency at different filtration rates; effects of flow changes; ammonia peaks and temperatures; aeration and chemical dosing requirements; recovery after a “kill” and operation in both downflow and upflow modes. The pilot filters demonstrated the process to be effective and robust and provided design parameters for the sizing of the process units and for the provision of chemical dosing and aeration equipment.

The paper sets the context to the scheme, describes the pilot filter work and the results, discusses the reaction kinetics and shows how the design parameters obtained from the pilot filter work were used in the development of the engineering design of the treatment works.
Funnel and radiation: a new technique for groundwater remediation
Authors: Maier D. , Maier M. , Sörensen M.
Published: May 2018

For the remediation of the groundwater of the former gas plant site of the city of Karlsruhe, which is contaminated with Polycyclic Aromatic Hydrocarbons (PAHs), a funnel-and-gate system was designed. In addition to the primary contamination with PAHs from the site itself a secondary contamination with vinylchloride (VC) is present in the aquifer as a result of a plume of degraded volatile organic compounds (VOCs) transported into the contaminated area from outside. For the removal of the contaminants an advanced novel technique consisting of an in-situ-UV-radiation in combination with adsorption on activated carbon was used. In this paper the first results of the experiments of the application of pilot scale equipment for the in-situ-UV-radiation for the oxidation of PAHs and VC are presented.
Pesticide removal by GAC preloaded with natural organic matter
Authors: Matsui Y. , Iwaki K. , Uematsu M. , Yuasa A.
Published: May 2018

The removal of hydrophobic and hydrophilic pesticides (simazine and asulum) by granular activated carbon (GAC) adsorbers preloaded with natural organic matter (NOM) was studied through experiments using pilot scale columns and microcolumns. The pesticide concentration increased with time after the pesticide application, and it reached a pseudo-steady-state plateau. Less than 8% of the adsorbed simazine desorbed back into the column effluent by 15 days after the influent was switched to simazine-free water. The simazine desorbed from the upper part of the bed was re-adsorbed in the lower part, keeping the effluent concentration at a low level. In the pseudo-steady-state, the removal rate was described by a first order kinetic reaction for the pesticide concentration. The evaluation of removal rate modulus value revealed the profile of loaded pesticide-competitive NOM with depth. The pesticide-competitive NOMs were different for each pesticide. The percentage of the simazine-competitive NOM to the whole NOM increased after UF membrane filtration (molecular weight cutoff 1K), but not for the asulum-competitive NOM.
Comparison between PAA/UV and H2O2/UV disinfection for wastewater reuse
Authors: Lubello C. , Caretti C. , Gori R.
Published: May 2018

The effect of peracetic acid (PAA) on indicator bacteria in secondary sewage effluent has shown PAA to be a viable alternative to other biocides. The synergy between UV/PAA and UV/H2O2 in laboratory experiments and at a pilot plant fed by the secondary effluent of two civil wastewater treatment plant has been investigated. This experiment is part of a larger research project on advanced treatment for municipal wastewater reuse in agriculture. A very high level of disinfection is necessary because of Italy's strict limits on unrestricted wastewater reuse in agriculture (2 CFU Total Coliform/100 ml). We found out that a combined treatment is satisfactory and that it is more efficient when chemical products such as PAA or H2O2 are introduced before UV irradiation, taking advantage of the hydroxyl radicals formation due to photolysis. At a cost parity PAA/UV advanced oxidation process shows the same disinfectant action as H2O2/UV while at a dose (amount) and cost parity, PAA shows a significantly better disinfectant action than H2O2.
In the (adsorption) competition between NOM and MIB, who is the winner, and why?
Authors: Newcombe G. , Morrison J. , Hepplewhite C. , Knappe D.R.U.
Published: May 2018

The adsorption of an odour compound common in drinking water, 2-methylisoborneol (MIB), was studied on four activated carbons in the presence of six well characterised natural organic matter (NOM) solutions. It was found that, although the carbons and the NOM solutions had a wide range of characteristics, the major competitive mechanism was the same in all cases. The low molecular weight NOM compounds were the most competitive, participating in a direct competition with the MIB molecule for adsorption sites. Equivalent background concentration (EBC) calculations indicated a relatively low concentration of directly competing compounds in the NOM. Some evidence of pore blockage, and or restriction was also seen, with microporous carbons most affected by low molecular weight NOM, and mesoporous carbons impacted by the higher molecular weight compounds.
Optimisation of coagulation and chlorination in drinking water treatment: laboratory and full-scale studies
Authors: Basson N.D. , Schutte C.F.
Published: May 2018

The paper deals with laboratory and full-scale studies aimed at optimising treatment processes at the Balkfontein plant of Sedibeng Water in South Africa. The raw water is highly eutrophic and contains a large fraction of treated effluent from domestic and industrial sources as well as agricultural runoff. The eutrophic nature and changing raw water quality give rise to many operational difficulties and high treatment costs as well as problems with the final water quality. Optimisation of the coagulation and chlorination processes was seen as a cheaper solution to these problems than to install advanced processes such as ozonation and activated carbon adsorption that would add greatly to treatment costs. The laboratory studies indicated that through optimisation of coagulation-flocculation and by replacement of pre-chlorination by intermediate chlorination (after primary sedimentation) most of the treatment problems could be solved and final water of the required quality produced without a large increase in treatment costs.
Ammonia oxidation at low temperature in a high concentration powdered activated carbon membrane bioreactor
Authors: Seo G. , Takizawa S. , Ohgaki S.
Published: May 2018

In this study, a membrane bioreactor (MBR) with high concentration of powdered activated carbon was investigated to enhance the oxidation of ammonia at a water temperature lower than 4°C. A semi-pilot scale submersed suction type MBR was operated with a hollow fiber membrane module having a nominal pore size of 0.1μm and an effective filtration area of 0.05 m2. A powder activated carbon (PAC) concentration of 40 g/L was maintained in the reactor and the PAC was not replaced during the experiment. A control reactor without PAC was also operated for comparison. Water temperature of both reactors was controlled at 25, 10, 4 and 2°C. At a water temperature of 4°C, the influent ammonia nitrogen of 10 mg/L was removed completely in the reactor with PAC. On the other hand, the effluent concentration of the control reactor was fluctuated in a range of 3-6 mg/L. In addition, nitrite nitrogen was detected in the control reactor up to a maximum concentration of 6 mg/L at the same temperature. Still high removal efficiency was obtained in the reactor with PAC even at 2°C, but almost no ammonia oxidation was observed in the control reactor. The average ammonia oxidation rate of the powdered activated carbon reactor was 1.3-3.2 mg/L.h, which is 4.5 times higher than that of the control (0.51-0.63 mg/L.h). Filtration resistance was 2.45 × 1012m-1 for the reactor with PAC, which is one order lower than that of the control reactor (1.64 × 1013m-1). The microbial cake layer on the membrane surface caused the larger filtration resistance for the control reactor. Only one chemical cleaning was conducted for the membrane in the PAC reactor at the flux of 0.4-0.7 m/d while 3 times cleaning was required for that of the control.
Arsenic removal by iron hydroxides, produced by enhanced corrosion of iron
Authors: Karschunke K. , Jekel M.
Published: May 2018

Results of lab-scale experiments for arsenic removal from drinking water are presented. Arsenate(V)-ions were adsorbed on ferric hydroxides which were formed in-situ by corrosion of elemental iron in oxygenated water. Natural corrosion of fine iron wool was suitable to remove effectively high but realistic arsenic concentrations of 500 μg/L from drinking water. As the corrosion rate decreased significantly in time, two different methods to enhance the corrosion were tested and evaluated: galvanic corrosion using iron-copper contact elements and the application of an external voltage. The iron-copper contact elements showed promising results (a high and stable corrosion rate) but were bearing the risk of copper release when the contact broke down. The application of voltage led to an enhanced release of iron-ions but was coupled with a cathodic formation of hydrogen from water. The generation of hydrogen is a very undesirable effect for any practical application. Irrespective of the mode of corrosion, a post-treatment step (sand filtration) was required to remove the arsenic loaded rust particles from the effluent. In the final effluent, drinking water quality was reached by all the methods.
Concept for an integrated evaluation of arsenic removal technologies: demonstrated in a case study
Authors: Ruhland A. , Jekel M.
Published: May 2018

A concept for a technical, ecological and economical evaluation of arsenic removal technologies is introduced and demonstrated on the basis of three alternative arsenic removal processes, direct filtration with FeCl3, adsorptive filtration with FeSO4 and adsorption on granulated ferric hydroxide, which were tested in a case study. A set of evaluation criteria is worked out and discussed with regard to the case study. Further, a multi criteria decision support instrument is described and used for identifying the preferential arsenic removal process. The ranking of the analysed alternatives is presented. The results base on the data of a full scale treatment plant of a water supplier in the Lower Saxony, Germany. The adsorption on granulated ferric hydroxide is ranked as preferential process - alternative for arsenic removal on the conditions of the case study.
Arsenic removal - experience with the GEH® process in Germany
Authors: Driehaus W.
Published: May 2018

The reduced German drinking water standard for arsenic of 10 μg/L initiated the development of a new adsorbent, the granular ferric hydroxide. It was introduced into the market in 1997 under the trade name GEH®. 16 drinking water treatment plants for arsenic removal are now using this technique in Germany. The article gives a brief overview over this applications, the design data and the treatment results. This technique requires only small contact times between 3 and 10 minutes, whereas the treatment capacities are up to 250,000 bed volumes. The average treatment costs, including media supply, media exchange service and disposal, are 0.04 EURO per m3 treated water.