bluuebunny/crossref_metadata_2025 huggingface dataset:
Vulnerability to diffuse pollution and average nitrate contamination of european soils and groundwater
Authors: Meinardi C. R. , Beusen A. H. W. , Bollen M. J. S. , Klepper O. , Willems W. J.
Published: May 2018

From the Atlantic Ocean to the Ural Mountains, European soils are threatened by diffuse pollution from modern agriculture and increased atmospheric deposition. The vulnerability of the soil to diffuse pollution depends on land cover, topsoil features, net precipitation, aquifer type, groundwater recharge and age. The elaboration of the various elements was realized by applying Geographical Information Systems (GISs). Precipitation and the actual evapotranspiration were estimated using meteorological data. The resulting net precipitation is discharged by groundwater recharge and surfacial runoff, with the division of net precipitation in groundwater recharge and surfacial flow following from climate and soil features. The average groundwater age was based on aquifer depth, porosity and the recharge. The vulnerabilities of the soil and groundwater were estimated by establishing a ranking of the combined risks of a diffuse contamination for the topsoil and for groundwater in aquifers. Nitrogen compounds in soils are caused mainly by manuring and fertilization of agricultural lands and atmospheric deposition. The varying doses of fertilizer and manure and the atmospheric deposition of nitrogen compounds were assessed for an actual situation. Only part of the applied doses leached into the soil. The leaching of nitrate to a level of 1 m below land surface was estimated by applying empirical relations derived from the northwest European experience, based on land use, features of the topsoil and net precipitation. The subsequent leaching to deeper strata and a further denitrification also depend on groundwater recharge and aquifer type. The average nitrate concentration in the various aquifers was assessed by estimating the nitrogen doses to European soils in the course of time in combination with the groundwater age. Results, attained using GIS and presented in the form of maps, show the leaching of nitrate concentrations to a level of 1 m below land surface and also the average concentration in the upper aquifer system.
Policy analysis as a tool for habitat restoration: a case study of a danube river floodplain, Hungary
Authors: Marchand M. , Marteijn E. C. L. , Bakonyi P.
Published: May 2018

This paper will elaborate a policy analysis approach especially designed for habitat restoration. It will be illustrated by a case study example of a floodplain area along the Danube river, Hungary. The case study used hydrodynamic and water quality models and expertise from a range of disciplines. This made it possible to unravel the complex relations between the environment and human interventions. Crucial was the participation of local experts in the design and screening of measures, as well as the feedback from local interest groups at several occasions during the project. This resulted in the formulation of rehabilitation ideas, most of which have hitherto not been discussed. The combination of creative thinking with practical possibilities and limitations has been worked out in a cyclic process from which three different alternatives emerged. These have been analyzed for their feasibility with regard to the goals to be achieved, their costs and their impacts on other interests.
Large-scale wetland-restoration of the Ronde Venen, The Netherlands
Authors: Bijlmakers L. L. , de Swart E. O. A. M.
Published: May 2018

For the area of the Ronde Venen a plan for large-scale wetland-restoration and improvement of the water quality was developed. Major elements of the developed spatial strategy are the optimal use of the specific hydrological and ecological characteristics of the area. Based on regional hydrological characteristics within the study area hydrological sub-units were distinguished by connecting discharge and recharge areas. In this way the intake of polluted surface water from outside the area could be minimized, with an optimal use of specific local differences in water quality. Two scenarios were developed and evaluated using hydrological, hydrochemical and ecological models. The scenarios differed in spatial composition and the way the water level was manipulated. In order to optimize water quality, natural and artificial pollution control mechanisms were implemented as well. An important criterion for the evaluation was the extent to which the scenarios succeeded in optimizing conditions for the realization of the ecological goals. The most promising and acceptable scenario has been worked out in further detail.
Artificial mixing: a therapy measure combating cyanobacteria in Lake Nieuwe Meer
Authors: van der Veer Bart , Koedood Jan , Visser Petra M.
Published: May 2018

In Lake Nieuwe Meer near Amsterdam, the bloomforming cyanobacterium Microcystis aeruginosa dominates the phytoplankton in late summer and forms scums that can be a big nuisance. In Lake Nieuwe Meer the water column is stratified in summer. Microcystis can stay in the euphotic zone due to its buoyancy. Deep mixing of the lake abolishes this advantage of buoyancy of Microcystis and favours non-buoyant algae as they will have a reduced sedimentation loss.

The technique of artificial mixing has been applied in 1993 and 1994 applied in Lake Nieuwe Meer in order to reduce the growth of Microcystis. The application was successful: there has been no nuisance due to Microcystis scums. The percentage cyanobacteria of the total phytoplankton in summer decreased from ±90% without mixing to less than 5% with mixing. Characteristics of the equipment used for destratification are presented.
An integrated water management concept to ensure a safe water supply and high drinking water quality on an ecologically sound basis
Authors: Heinzmann Bernd , Sarfert Ferdinand
Published: May 2018

For the city of Berlin and the surrounding areas a growth of the number of inhabitants is expected, resulting in a considerable increase in the water consumption. However, a sufficient quantity and an excellent quality of drinking water in the future can only be guaranteed through more integrated management of water resources. Artificial recharge of groundwater plays a key role in this approach. It includes the infiltration of treated surface water in a direct coordination to water catchment facilities. Investigations show, that other possibilities are: i) the reuse of sewage water, although there are still unsolved judicial issues, and ii) the use of stormwater. For both, an advanced treatment is necessary to meet the stringent quality requirements. Thus, the treatment is shifted more towards the sources of pollution, that means from the treatment of surface water to wastewater and stormwater to obtain an optimum water resource protection. Furthermore, the water is partly returned to the water cycle in order for it to remain within the region. Treated surface water, advanced treated wastewater, purified stormwater and treated weakly polluted combined wastewater from the combined system constitute favourable sources, in combination, for the replenishment of groundwater. Former wastewater irrigation fields in the area could be used. This also prevents re-dissolution of heavy metals in the polluted soil of the wastewater irrigation fields into the groundwater.
Enhancing research utilization for integrated water management
Authors: Wisserhof Johan
Published: May 2018

Water-related research is often performed at significantly lower levels of integration than policymaking for integrated water management. This may limit its utilization in policymaking. Nevertheless, an analysis of strategic policymaking for water management in The Netherlands shows that policy research still has a considerable impact on policy. This is largely due to the integrative intermediary role of policy analysis. (Policy research is the acquisition of knowledge concerning a policy problem. Policy analysis is the appraisal of alternative policies.) However, policy analysis for water management is often restricted to the natural sciences and engineering. An additional input of administrative science may contribute to resolve the current problems in implementation of integrated water policies. Factors of concern in this respect are elaborated.
Water quality standards: sense and nonsense
Authors: Lijklema Lambertus
Published: May 2018

The functions and utility of emission and immission standards are discussed as instruments in the management of water quality. Especially the intrinsic a-priori trade-off associated with setting immission standards, the complexity of the cause-effect relationships and the variability of water quality are used as an argument to rely less heavily on such standards. It is argued that simulation, systems analysis, Habitat Suitability Criteria and plan effect matrices are tools that can be implemented and used more effectively.
Geohydrological information systems for water management
Authors: van Bracht M. J.
Published: May 2018

The increasing complexity of water management has generated a rapidly growing demand for information and also for Geohydrological Information Systems (GhIS). An information system for water management must relate directly to the water manager's tasks. To be able to implement these tasks effectively the water manager requires information about the properties of the water system and about society's interests and needs. As well as providing information, a GhIS for water management should have analytical tools for interpreting and analyzing data and information, so it also has functions for acquiring, storing, processing, checking, interpreting and analyzing data. TNO Institute of Applied Geoscience is developing GhIS that have these functions and in which the integration of information and functionality, the flexibility, and the transferability and utility for different user groups are also important aspects.
A mathematical concept of runoff prediction model for small tropical catchment areas
Authors: Sudjono Priana
Published: May 2018

After the Horton overland flow concept became legend until the early 1960s, new findings then revised this concept for implementation in several catchment area conditions. Runoff processes in tropical regions seem to have specific characteristics such as thick humus on the top layer of the catchment area and non-uniformity of hydraulic conductivity vertically and horizontally across the stream. To overcome the runoff problems in tropical regions, a reasonable model needed to be developed to predict generated runoff. Based on the concept that saturation condition in a catchment generates non-uniformly during the course of a rainfall, and that the storage capability of top layer in intercepting rain-water leads to subsurface and return flow, the water balance in a segment of the catchment area is calculated. The mechanism of flow in the model is that subsurface flow and return flow, which are a function of hydraulic conductivity, and surface runoff on a segment are integrated for the whole areas. The generation of flow using the model seems to indicate that runoff peaks will commence after each segment is saturated starting from the valley bottom. The lag time for initial flow to alter significantly depends on the data on stream-flow before the storm began that indicate the soil moisture and depth of the temporary water table. Generally, though, the model is very flexible, so that data on each segment subject to the wide variety of physical conditions of the catchment area characteristic of tropical regions can easily be implemented.
Effect of size/age and feed composition on body composition and phosphorus content of rainbow trout, oncorhynchus mykiss
Authors: Rønsholdt B.
Published: May 2018

In fish the environmental load of nitrogen (N) and phosphorus (P) may be calculated indirectly by a mass balance, subtracting the content of N and P accumulated relative to the amounts fed. The present study examined the effect of size/age and feed composition on body composition and P content in rainbow trout. A 2×2 factorial design was used with two size/age groups (avg. wt. 282g [1 yr]; 980g [2 yr]) of sib fish, fed an experimental high energy diet or a commercially available diet with protein:fat ratios of 40:25 and 46:25 respectively. Fish were fed 3×/day to avoid feed loss using isocaloric and restricted feeding (1.0%/body weight [1 yr] and 0.7%/body weight [2 yr] at start) using a commercial feeding table. Results indicated that both size/age and feed composition had highly significant effects (p < 0.001) on body composition. Older fish had higher fat and protein content than 1 yr olds, while a protein rich diet (protein:fat, 46:25) gave lower fat and higher moisture content than did a high fat diet (protein:fat, 40:25). Body composition also correlated with the K-factor (p < 0.001) showing that slender fish contained less fat. P content increased with K-factor. Feed composition had a significant effect (p < 0.05) on the P content with fish fed the high fat diet containing the highest amount, with a difference of 0.06 g/kg.
The impact of restricted rationing upon growth, food conversion efficiency and body composition of rainbow trout
Authors: Tomec M. , Teskeredžic Z. , Teskeredžic E. , Hacmanjek M. , McLean E.
Published: May 2018

Juvenile rainbow trout, Oncorhynchus mykiss, maintained under commercial conditions, were subjected to four different feeding regimes. Duplicate groups of fish were fed to satiation 3 times/d for either 7, 3, 2 or 1 d/wk over a 10 wk period. At the end of the trial, evaluations were made of group growth performance, body composition, and feed conversion efficiency (FCE). At the end of the experiment, no differences were discerned between fish fed either daily or 3 times/wk with respect to growth, FCE or body composition. Animals placed upon the two lowest rations were significantly smaller (P<0.05) than those fed daily and exhibited decreased condition factors and body lipid levels (P<0.05) and increased moisture content (P<0.05). Food conversion was least efficient in those fish provided the largest ration.
Variation in the operating income and the environmental impact of trout culture from a Danish fish farm utilising different production strategies
Authors: Færgemand Jacob
Published: May 2018

The age at which fish are transferred to seawater and the feeding strategies employed during the breeding season affect the economics underlying production of rain trout, as well as the environmental loading of phosphorus and nitrogen. An experiment was undertaken to evaluate the effects of i) age at seawater transfer, ii) feeding level and iii) use of a finishing feed, upon production economics. Monosex female rainbow trout (500-900g grown to 3500g) transferred to seawater at either 1 or 2 years of age, were examined. Feeding level was either that normally used by the farm or reduced by 20%. A commercial feed type with a protein-fat content of 48-28% was used throughout the experiment. Seven weeks prior to slaughter, fish were placed on a finishing diet with a protein-fat content of 60-9%. A set of economic-environmental models were established to evaluate the effects of the different production protocols upon farm profitability. Calculations were based upon fish performance evaluated as daily growth rate (% body wt/d), feed conversion rate, mortality, and weight data by means of visceral loss and gonadal development. The results of the present study illustrate that it is not possible to optimize both environmental impact and economic benefit during the production of trout.
Clustering of towns and villages for centralized wastewater treatment
Authors: Abd El Gawad Hassaan A. , Butter J. H. C.
Published: May 2018

In 1993 the Governorate of Fayoum completed its master plan for wastewater management. The master plan presents a staged implementation schedule for the development of wastewater facilities for the Governorate, covering needs up to the year 2020. The targets are ambitious: in order to meet sanitary health standards, nearly two million people (or 60% of the total population) living in 70 towns and villages would need to be served with sewerage systems. Providing all these areas with separate wastewater treatment plants would be impractical. The centralization of treatment at a limited number of treatment plants for clusters of towns and villages has advantages in terms of manageability, cost and environmental protection.

In the master plan the configuration of these clusters is presented. For that purpose a stepped approach has been developed: an approach in which aspects such as construction and operation costs of the facilities, existing infrastructure, the geography of the governorate, environmental impact, alternative treatment technologies and phasing of implementation have been considered. An important element of the stepped approach is an analytical model with which - from financial point of view - the optimum size of a cluster can be estimated. Variables of the model are sizes of towns and villages, distances and treatment technologies. The output of the model is a set of general design criteria which has been applied to the specific situation in the governorate.

The model has contributed to the establishment of the Master Plan for Wastewater: a plan now used by the Fayoum Sanitation Department as a framework to initiate new projects and to direct the activities of other agencies working in the sanitation sector in the governorate.
Copper and chromium (III) uptake by duckweed
Authors: Wahaab R. Abdel , Lubberding H. J. , Alaerts G. J.
Published: May 2018

The duckweed Lemna minor was cultivated under laboratory conditions with the amount of incident light as limiting growth factor. The fronds were found to double every 3 days under the highest radiation intensity. The plants were exposed to Cu and Cr(III) solutions of 0.25 and 1.0 mg ℓ−1 during 10 days. The plants needed to adapt for app. 8 days before attaining maximal, steady state removal. Cr(III) was removed more efficiently from the solution (75-100% in terms of concentration or load reduction) than Cu (35-40%), the higher efficiencies pertaining to the more dilute solutions. Uptake rates were 80-333 and 250-667 mg d−1 m−2 for Cu and Cr(III), respectively. The plants accumulated 1-2 g metal kg−1 plant (dry weight) when exposed to the high concentration. Cu seemed toxic at 1.0 mg ℓ−1, resulting in plant mortality after 8 days.
Comparative physiology of geosmin production by Streptomyces halstedii and Anabaena sp.
Authors: Blevins W. T. , Schrader K. K. , Saadoun I.
Published: May 2018

Geosmin and 2-methylisoborneol (MIB) are microbial metabolites that can cause earthy or musty off-flavors in aquatic food animals as well as seasonal taste and odor episodes in drinking water. This paper compares effects of selected environmental factors on biomass and geosmin production by the actinomycete Streptomyces halstedii and the cyanobacterium Anabaena sp., isolated from an aquaculture pond and from a source-water reservoir, respectively. For S. halstedii, optimal biomass production occurred at pH 6-7 and 30°C, and optimal geosmin synthesis occurred at pH 9 and 35°C. Low concentrations of both nitrate- and ammonium-nitrogen favored geosmin production, with higher concentrations stimulating biomass production. For Anabaena sp., optimal biomass production at 20 days occurred at 15°C and a light intensity of 17 μE/m2/s; optimal geosmin synthesis occurred at 20°C and 17 μE/m2/s. Chlorophyll a (chl a)/biomass varied inversely with light intensity. Maximal geosmin/biomass occurred at 20°C (17 μE/m2/s), and geosmin/chl a varied inversely with temperature. It was concluded that at 20°C, increasing light intensity favors lower chl a and greater geosmin synthesis by Anabaena sp.; at 17 μE/m2/s, increasing temperature stimulates chl a production (to 25°C) but represses geosmin synthesis (above 20°C).
Impact of improved sewerage systems on groundwater heads in Eastern Cairo region
Authors: Hassan M. M. , El Shiwi M. , Smidt E.
Published: May 2018

Large areas in Cairo have been experiencing groundwater and water table rise during the last decade. This has resulted in serious problems to the foundations of old houses, antiquities, and monuments. The main causes behind this rising water table and groundwater is the increased recharge from surface activities in a city experiencing increased population. Major sources of recharge in the urban area included leakage from water supply and sewerage pipes, while in the rural areas the major causes included domestic seepage from septic tanks and deep percolation of excess irrigation water in agricultural areas.

Various studies have been conducted to investigate the possible remedial solutions. The most recent study conducted by the Research Institute for Groundwater indicated that the most effective remedial measure is through the reduction of recharge. This was determined through simulation of various remedial measures.

In this paper, a preliminary assessment of the recently improved sewerage system is made. Results indicate considerable reduction in water table levels and groundwater heads in the region. Final assessment would require a thorough investigation of possible other changes in the environment including both quantitative and qualitative aspects.
Growth and 2-methylisoborneol production by the cyanobacterium Phormidium LM689
Authors: Zimmerman W. J. , Soliman C. M. , Rosen B. H.
Published: May 2018

Growth and production of 2-methylisoborneol (MIB) was characterized in the cyanobacterium Phormidium sp. LM689 isolated from Lake Mathews, California, USA. The effects of: 1) uptake of several organic amendments related to pigment biosynthesis, 2) Fe availability, and 3) copper algicides were examined. Growth was estimated by total chlorophyll and soluble protein accumulation. Pyruvate additions up to 1250 mM did not effectively alter biomass accumulation. Mevalonic lactone increasingly stimulated (protein) growth but not MIB output at the same range of concentrations. Geraniol did not inhibit overall cyanobacterial growth when added to 300 μM, but did slightly decrease chlorophyll accumulation. Farnesol exhibited an antibiotic effect at all concentrations from 10 to 100 μM. Phormidium was tolerant to 1 ppm Cu+2 added as copper sulfate or as chelated copper. Siderophore production and growth in Fe and chelator-free medium was also demonstrated.
Ponds in the twenty-first century
Authors: Oswald W. J.
Published: May 2018

Because they are economical reactors, properly designed ponds for waste management will grow in importance in the 21st Century. They will also be important for water and nutrient recycling and for animal feed production. Paddle wheel mixed algal growth ponds are not only a cost effective choice for wastewater oxidation but also are most efficient in fixing solar energy and in reclaiming water, nutrients, and energy from organic wastes. As the human population increases the amount of arable land will soon be less than one hectare per person and, at current world crop productivities of much less than 0.1 g/m2/d, one hectare of arable land per person will be insufficient to sustain a projected population of more than six billion by the year 2000. Because the amount of land is finite, the apparent solutions are to increase productivity and, ultimately, to attain a constant population. Microalgae in ponds can produce high protein biomass at a rate of 10 to 20 g/m2/d, productivities an order of magnitude greater than land crops. Algae can be combined with grains to produce valuable feed, which through poultry, animals, and fish can improve human nutrition. With improved human nutrition, financial security should increase and birth rates should decline; therefore, algaculture in ponds, together with conventional agriculture, can help reach a stable population and improve the quality of human life.
The effect of anaerobic pre-treatment on the inert soluble COD of fermentation industry effluents
Authors: Yilmaz G. , Öztürk I.
Published: May 2018

The objective of this study is to determine the inert soluble COD of wastewaters from the fermentation industry. In this context, a series of experiments were performed for various effluents from baker's yeast industry including raw process wastewater, anaerobic pre-treatment plant effluents, domestic and washing waters mixture. The inert COD ratio (SISO) for the raw effluents from baker's yeast industry was determined as 0.1. This ratio was in the range of 0.20 to 0.30 for the anaerobically pre-treated effluents. TheSISO ratios for the wastewater simulating the effluent of the existing full-scale aerobic treatment plant have varied from 0.18 to 0.48. Such a large variation has been originated from the operating conditions of the existing full-scale anaerobic treatment plants. The higher volumetric loading rates and shorter sludge retention times correspond the lower SISO ratios for the full-scale anaerobic treatment systems in general.
Methane fermentation, submerged gas collection, and the fate of carbon in advanced integrated wastewater pond systems
Authors: Green F. B. , Bernstone L. , Lundquist T. J. , Muir J. , Tresan R. B. , Oswald W. J.
Published: May 2018

There are several basic reasons for concern regarding the fate of carbonaceous material in waste stabilization ponds: accumulation of solids; performance and useful life of the pond system; and, the control of methane emissions. In conventional ponds methane fermentation is minimal, and carbon-rich organic matter is integrated by bacteria and microalgae which grow and settle. The integration of carbon decreases pond volume and treatment capacity and causes the ponds to age prematurely, to produce odor, and to require frequent sludge removal; and, any methane produced escapes to the atmosphere. However, if carbon-rich organics are efficiently converted to methane or to harvested microalgae, the pond system will continue to treat wastewater effectively for an extended period of time. Advanced Integrated Wastewater Pond Systems (AIWPSs) developed at the University of California fully utilize methane fermentation and microalgal cultivation to treat wastewater and to reclaim energy and nutrients. First generation AIWPSs have provided reliable municipal sewage treatment at St. Helena and Hollister, California, for 28 and 16 years, respectively, without the need for sludge removal. However, these first generation systems lack the facilities to recover and utilize the carbon-rich treatment byproducts of methane and algal biomass. The recovery of methane using a submerged gas collector was demonstrated using a second generation AIWPS prototype at the University of California, Berkeley, and the optimization of in-pond methane fermentation, the growth of microalgae in High Rate Ponds, and the harvest of microalgae by sedimentation and dissolved air flotation were studied. Preliminary data are presented to quantify the fate of carbon in the second generation AIWPS prototype and to estimate the fate of carbon in a full-scale, 200 MLD second generation AIWPS treating municipal sewage. In the experimental system, 17% of the influent organic carbon was recovered as methane, and an average of 6 g C/m2/d were assimilated into harvestable algal biomass. In a full-scale second generation AIWPS in a climate comparable to Richmond, California, located at 37° N latitude, these values would be significantly higher--as much as 30% of the influent organic carbon would be recovered as methane and as much as 10 g C/m2/d would be assimilated by microalgae. These efficiencies would increase further in warmer climates with more abundant sunlight.
Performance of two municipal sewage stabilization pond systems with high and low loading in South-eastern Spain
Authors: Soler A. , Torrella F. , Sáez J. , Martínez I. , Nicolás J. , Llorens M. , Torres J.
Published: May 2018

From January to December 1992, the efficiency of two waste stabilization pond systems (WSPS) located in the Region of Murcia, South-eastern Spain, has been studied in terms of the physicochemistry and the microbiology of the systems. The efficiencies of the different stages of the treatment and the global performance have been compared. The WSPS of Lorquí and Ceutí (12,000 inhabitants) receives fruit processing and cannery wastes mixed with the urban sewage. This increases the load up to 95,000 equivalent inhabitants with an average BOD5 of 800 mgO2/l. Global reductions of COD and BOD5 were 79% and 73% as a yearly average. The mean of the reductions of indicator microorganisms were: coliphages (CHP), 83.14%; total coliforms (TC), 72.90%; faecal coliforms (FC), 93.84% and salmonellae (SAL), 98.29%. The WSPS of San Javier (15,000 inhabitants), situated at the border of the Mediterranean, does not receive industrial wastes but suffers from intrusions of marine waters into the sewers. BOD5 is diluted by the intrusion to less than 100 mgO2/l, even in summertime when population doubles because of the tourism. Average yearly reductions of COD and BOD5 were 32% and 21%. The means of the microbiological reductions were: CHP, 81.60%; TC, 90.77%; FC, 94.37% and SAL, 99.42%. Design constants have been calculated for both systems considering the climatic conditions of the area.
Purple non-sulfur bacteria and their influence on waste stabilisation pond performance in the Yemen Republic
Authors: Veenstra S. , Al-Nozaily F. A. , Alaerts G. J.
Published: May 2018

In the semi-arid Yemen Republic wastewater treatment has high priority to control the spreading of communicable diseases and to make the effluent fit for reuse in agriculture. Experience with existing waste stabilisation ponds has in many cases been unfavourable because of poor BOD removal and odour problems. The raw domestic sewage at the Sana'a waste stabilisation ponds is very strong in terms of BOD, COD, TSS and sulfate, and its ammonia levels are excessively high (150-200 mg N-[NH3 + NH4+]L). The combination of high temperature, high organic loading rates and the presence of sulfides, due to conversion of sulfate in the anaerobic ponds, appears to favour development of anoxygenic photo-heterotrophic purple non-sulfur bacteria Rhodopseudomonas spp. in facultative ponds. Some species can oxidise sulfides to sulfate using light; they lend the water its typical reddish-pink colour and cause high turbidity which may disfavour algal growth. Also, in large tracts of the ponds the high ammonia levels suppress algal growth, as demonstrated in lab experiments. Consequently, low DO and poor C-metabolisation prevail in the ponds. Low DO in turn again creates conditions stimulating microbial sulfate reduction. Field data from other facultative ponds in Yemen suggests that a minimum retention time in the facultative ponds of 20-25 days is necessary to provide ecological conditions allowing algae to outcompete purple bacteria.
Nitrification studies on fertilizer wastewaters in activated sludge and biofilm reactors
Authors: Çeçen Ferhan , Orak Elvan , Gökçin Pinar
Published: May 2018

Nitrification characteristics of a high-strength fertilizer wastewater were studied in a batch activated sludge and a continuous-flow biofilm reactor. In a batch activated sludge system one of the most decisive factors was the pH control. The results in terms of ammonium decrease and nitrite build-up were fitted to kinetic models and it was shown that in the absence of inhibitory factors like high free ammonia or nitrous acid build-up the behaviour was similar to that in the case of low-strength wastes. Continuous-flow studies in the biofilm reactor at different loading rates and dissolved oxygen concentrations indicated that such a biofilm reactor could be employed in the treatment of highly nitrogenous fertilizer wastes. Depending on operating conditions such as dissolved oxygen concentration and loading rate an effluent ammonia concentration as low as 4 mg NH4−N/L could be achieved. In the dissolved oxygen ranges of 3.2 mg/L–3.5 mg/L the system reached the maximum removal rate of 0.17 kg NH4−N/m3.d. When the dissolved oxygen was increased to 4.9 mg/L, removal rates as high as 0.41 kg NH4−N/m3.d could be obtained. Also in continuous-flow operation nitrite accumulation reached in some cases a considerable degree depending on the bulk nitrogen and dissolved oxygen concentrations. The nitrite accumulation in the effluent stream varied from 4–180 mg NO2−N/L depending on operational conditions.
Modelling the performance of anaerobic wastewater stabilization ponds
Authors: Saqqar M. M. , Pescod M. B.
Published: May 2018

The performance of the primary anaerobic pond at the Alsamra Wastewater Treatment Plant in Jordan was monitored over 48 months. Overall averages for the removal efficiencies of BOD5, COD and suspended solids were 53%, 53% and 74%, respectively. An improvement in removal efficiency with increase in pond water temperature was demonstrated. A model, which takes into account the variability of raw wastewater at different locations, has been developed to describe the performance of a primary anaerobic pond in terms of a settleability ratio for the raw wastewater. The model has been verified by illustrating the high correlation between actual and predicted pond performance.
Purification by a natural waste stabilization pond: influence of weather and ageing on treatment quality and sediment thickness
Authors: Schetrite S. , Racault Y.
Published: May 2018

The natural waste stabilization pond of Vauciennes, located in the north of France, underwent regular monitoring from October 1981 to July 1991, within the framework of a programme studying the evolution of operation parameters related to the ageing of plants. This study enabled us to assess the variations in the quality of the discharge depending on the season, in particular concerning the nitrogen and phosphorus parameters. The input/output reports made it possible to make specifications concerning the variations of the loads to be treated and the overloads caused by rainy episodes, and the real performances of the plants in relation to rainfall, evaporation, hydraulic exchanges with the soil and interannual seasonal variations. The evolution of the treatment, characterised by the parameters of the treated effluent, was observed, on the basis of equivalent climate conditions. Lastly, the growth of the deposits and their location in the first pond observed based on the systematic establishment of a cartography of the bottom of the pond.
Vibrio cholerae 01 and salmonellae removal compared with the die-off of faecal indicator organisms in waste stabilization ponds in northeast Brazil
Authors: Arridge H. , Oragui J. I. , Pearson H. W. , Mara D. D. , Silva S. A.
Published: May 2018

Vibrio cholerae O1 was reduced from 40 per litre to zero after 5-10 days, and salmonellae from 130-470 per 100 ml to 1-2 per 100 ml after 13-16 days. Faecal coliforms were better indicators of these bacterial pathogens than were faecal streptococci or Clostridium perfringens, and FC numbers of 1000 per 100 ml were associated with an absence of V. cholerae and 1-2 salmonellae per 100 ml. In-pond survival studies indicated that significant removal of V. cholerae occurs when the sulphide concentration is ≥ 3 mgl-1, thus indicating the need to include anaerobic ponds.
Consideration of DAF retrofit to a large conventional water treatment plant
Authors: Vallance B. C. , Pritchard R. G. , Hargesheimer E. E. , Seidner R. T.
Published: May 2018

Recent historical trends have shown a deterioration of raw water quality feeding the 60 year old Glenmore WTP. This deterioration has manifested itself in a chronic increase in nutrient loads and consequent chlorine demand. The plant's existing pre-treatment and sedimentation facilities have had difficulty in handling flash turbidity spikes. Lack of contact time for post chlorination has created a reliance on high pre-chlorination practice to ensure a safe distribution system disinfectant residual. These trends, together with the regulatory authority's tightening of compliance standards and enforcement policies, plus growing public expectations for consistently high quality drinking water, pointed towards a need for a comprehensive assessment of the plant.

The City of Calgary, with its Engineering Consultant, embarked on a programme to review the existing plant facilities; identify alternatives with potential for addressing known concerns; and pilot both conventional and advanced treatment processes side by side, to establish relative and definitive performance data.

This paper addresses the piloting aspect of the study programme, and in particular, the rationale for piloting dissolved air flotation (DAF). Conceptual development, design and construction of the pilot plant are all discussed. The conceptual development was based on the needs and design constraints imposed by the existing plant, such as hydraulic profile. The approach to design was predicated by a desire for a pilot plant that would provide not only guidance for the plant upgrade, but also a working tool for future studies, process monitoring and optimization. The construction and commissioning was planned with a view to having the pilot plant operational in time for spring run-off.

Some of the operational experiences with the pilot plant are discussed. These included modifications to the DAF baffle weir; the collection, display, manipulation and graphing of data from online monitors; filter performance following DAF pre-treatment, and the establishment of a successful set of operating conditions.
Dissolved air flotation in potable water treatment: the Dutch experience
Authors: van Puffelen Jan , Buijs Paul J. , Nuhn Peter N. A. M. , Hijnen Wim A. M.
Published: May 2018

This paper reviews the experience the drinking water companies in The Netherlands have gained in the last twenty years in the field of dissolved air flotation. An overview of the Dutch flotation plants with their individual objectives is presented. The efficiency of flotation towards the removal of different parameters, such as turbidity, organic matter and micro-organisms is good, which is illustrated by data from the water companies. Both in the past and at present water companies compare flotation to other floc separation techniques, such as sedimentation or direct filtration. Specially for waters with (relative) low turbidity and high chlorophyll-a content, flotation proved (in combination with rapid sand filtration) to be very effective. The efficiency of the flotation process has been improved by the development of different nozzle-types. Some of these types are described here, each with their advantages and disadvantages. In general dissolved air flotation has proved to be as sturdy and reliable as sedimentation techniques, such as lamellae settling.
Counter-current dissolved air flotation/filtration
Authors: Eades Andrew , Brignall W. J.
Published: May 2018

Thames Water Utilities has developed and patented a Counter-current dissolved air flotation/filtration (COCO-DAFF) process as a compact water treatment system designed to remove particulate material from traditional water sources. In particular it has been developed to overcome operational problems with primary filters caused by seasonal blooms of filter blocking algae such as Melosira sp., Aphanizomenon sp. andAnabaena sp. The process can be run without flotation during periods when algae are not a problem, giving operational cost savings. This process differs from co-current dissolved air flotation in that the recycle water is introduced after the inlet structure, but above the filter media. This generates an even depth bubble blanket in the flotation tank through which all the flocculated water must pass. The advantages are that in moving the recycle inlet away from the flocculated water inlet the potential for floc damage by the recycle is eliminated. Also since the entire sludge blanket is supported by a deep, even, bubble blanket, on de-sludging any fall-out of sludge that occurs near the de-sludging weirs will have to go back down through the process, leading to subsequent re-floating, and a reduced potential for spiking of the floated turbidity. Process validation experiments have been carried out on a 1.4 Ml/d pilot plant based at the Kempton Advanced Water Treatment Centre, London. These tests have identified a required flocculation time of 15 minutes prior to counter-current flotation, and insensitivity to the depth of the air injection below top water level. Dissolved air distribution is achieved using a special high volume flow rate DAF nozzle designed to lower the number of nozzles required per unit area, and to maximise the spread of the bubble cloud for optimum bubble/particle contact. Computational fluid dynamics (CFD) has been used in the scale-up of the pilot plant experience into the first full scale of this design plant to be built, by PWT Projects, at the 200 Ml/d Walton AWTW, for Thames Water Utilities.
The first DAF water treatment plant in the United States
Authors: Nickols David , Moerschell Gerard C. , Broder Michael V.
Published: May 2018

The Millwood Water Treatment Plant in Westchester County, about 60 kilometres (35 miles) north of New York City, was commissioned in August 1993. This plant is the first dissolved air flotation (DAF) plant in the United States which uses the DAF technology and concepts that have become the industry standards in Europe and Australia. The $19-million plant was built to treat a previously unfiltered supply, to meet the requirements of the new federal Surface Water Treatment Rule.

This paper describes the project in its entirety: starting from the planning, pilot testing, and process selection; proceeding to the means of overcoming resistance to a “new” process and obtaining regulatory body approvals; and outlining the design, process criteria, construction, and start-up of the plant. Operating results are also presented. The plant treats soft, slightly colored, generally low turbidity water which experiences occasional turbidity spikes of 100 NTU or more. The treatment process comprises two-stage mixing, three-stage flocculation, dissolved air flotation, ozonation for primary disinfection, dual-media filtration, and post-treatment with chlorine, sodium hydroxide, orthophosphate and fluoride. Flotation sludge is dewatered in on-site freeze/thaw lagoons for off-site disposal in a landfill.
Municipal wastewater treatment by lime/ferrous sulfate and dissolved air flotation
Authors: Cáceres Luis , Contreras René
Published: May 2018

In this work a chemical treatment system for municipal wastewater using copper cementation effluent and lime as coagulants in combination with dissolved air flotation, was investigated. Copper cementation effluent (CCE) containing about 45% dissolved solids (density=1.31) is a liquid waste from a leaching process, which is disposed in large ponds by several copper mines in the North of Chile. CCE contains a combination of ferrous iron, sulfate, chlorine, magnesium, sodium, residual copper and other ions. For its use as a coagulant, CCE was treated using a low cost process. Ferric hydroxide flocs precipitated after CCE addition were efficiently removed by dissolved air flotation producing a low density froth. High suspended solid removal efficiency, process flexibility, short overall residence time in addition to low cost of chemicals used and precipitation of varied proportions of contaminants, including bacteria from wastewater, are the main features of this chemical treatment system.
Application of dissolved air flotation for treatment of wastewater from meat processing industry
Authors: Wasowski J.
Published: May 2018

The paper concerns the application of dissolved air flotation for treatment of waste water from the meat processing industry. The main aim of the study was identification of the flotation mechanism aided by the coagulation in the layouts with and without recycling, and finding and defining the role of the technological factors influencing flotability of pollutants found in the given waste waters. The results of the studies, supported by the mathematical analysis, form the basis of rational design and conduction of flotation in practice.
River Basin management and estuarine needs: the Great Brak case study
Authors: Huizinga P.
Published: May 2018

The study of the effect of the Wolwedans Dam on the Great Brak Estuary and the development of the management plan to maintain a healthy environment yielded many interesting results. The general conclusion is that developments in a catchment, especially those affecting the runoff, can have serious effects downstream. The study also proves that detailed investigations can result in an effective management plan to maintain a healthy environment.
Towards managing catchment water utilisation for the Lake St Lucia ecosystem
Authors: Weston D. R. , Quibell G. , Pitman W. V.
Published: May 2018

Lake St Lucia is one of Africa's largest coastal lakes, and is one of South Africa's most important wetland ecosystems. However, like many ecosystems, it is under threat from increased demands for water in its catchment area. Reduced runoff primarily impacts on the salinity regime of the lake. At low lake levels there is a net inflow of seawater to the lake. Evaporation concentrates the salts, and lake salinities rise to several times that of seawater. In water periods, lake levels rise and there is a net outflow toward the sea. Under these conditions salinities are low. The lake therefore naturally experiences a range of salinities associated with wet and dry cycles. Increased water use in the catchment will, however, impact on this natural salinity regime. This paper introduces a suite of models which will be used to facilitate management of the water resources of the catchment. The preliminary work presented demonstrates the ability of the models to provide meaningful input into a catchment management decision-support system.
Valuing environmental benefits from river quality improvements
Authors: Tyson J. M. , Foster V.
Published: May 2018

Current approaches to meeting environmental expectations lack a sound, consistent methodology by which the environmental benefit may be quantified in economic terms, thereby enabling cost benefit/cost ratios to be determined and included in the decision-making process. This is being addressed in the United Kingdom through a programme of collaborative research involving the Department of the Environment, the Water Services Association and the Environmental and Economic Regulators. An Interim Benefit Assessment Manual has been produced and is being evaluated by case studies, reporting in 1995 with a revised version of the manual planned to be available in 1996.
Effect of advanced oxidation processes on inactivation of coliphages
Authors: Rajala-Mustonen Ritva L. , Heinonen-Tanski Helvi
Published: May 2018

Chlorine and its derivatives are no longer regarded as acceptable disinfectants of water because of compounds they form with organic material in water. These compounds have been proved to be mutagenic and carcinogenic to man. Alternative disinfectants like UV radiation and ozonization are regarded as less harmful disinfectants of microorganisms in water.

In the present study the effect of UV radiation alone and together with hydrogen peroxide, and ozone treatment on the inactivation of coliphages in tap water were studied. Two phage types, DNA- and RNA-phages were seeded into tap water and exposed to these disinfectants in batch experiments. The inactivation of phages was determined as a reduction of phage titer as a function of contact time.

Disinfection with ozone proved to inactivate coliphages more rapidly than UV light or UV light together with hydrogen peroxide (H2O2). After two minutes exposure time the reduction in phage titer was from 6 to 8 log units with ozone while with UV light or UV with H2O2 the reduction was from three to four log units.

According to these results ozonization seemed to be more efficient disinfectant than UV light radiation.