bluuebunny/crossref_metadata_2025 huggingface dataset:
Anaerobic treatment of chemical and brewery waste water with a new type of anaerobic reactor; the biobed® EGSB reactor
Authors: Zoutberg George R. , Frankin Rob
Published: May 2018

In this paper a new ultra high loaded type of anaerobic reactor, the Biobed® EGSB (Expanded Granular Sludge Bed) reactor, is presented. Also presented is the full scale implementation of this reactor in two different types of industry; namely chemical industry and brewery.

The chemical factory involved is Caldic Europoort in the Netherlands. In this factory formaldehyde is produced from methanol. The waste water is characterised by high concentrations of these compounds (formaldehyde till 5 g/l and methanol till 10 g/l). Due to the special configuration of the employed anaerobic reactor it is possible to acquire a removal efficiency for both compounds of more than 99%.

At the brewery involved the Biobed® reactor is installed before an existing aerobic treatment. Here, the reactor serves as “COD remover”, which results in a decreased COD load to the aerobic post-treatment causing lesser sludge production and lesser energy consumption.

It is concluded that the Biobed® EGSB reactor is a new ultra high loaded anaerobic treatment system in which it is possible to obtain high volumetric COD removal rates and in which it is possible to treat waste water containing toxic but degradable chemical compounds.
Performance of anaerobic packed-bed system with different media characteristics
Authors: Tay Joo-Hwa , Jeyaseelan S. , Show Kuan-Yeow
Published: May 2018

The effects of media specific surface area, porosity, and pore size on the performance of upflow anaerobic packed-bed reactors (APBRs) were examined in the laboratory. The results showed that, the APBR containing media of the lowest surface area but the largest pore size and porosity, demonstrated the highest chemical oxygen demand (COD) removal efficiencies of 90% and 73% at loading rates of 8 and 16 g COD/L.day, respectively. An increase of over 40% in specific area in an APBR had not improved the removal efficiency, instead it produced 16% lower in COD removal efficiency at loading rate of 16 g COD/L.d. A study on the effects of effluent recycle indicates that the APBR having the largest pore size and porosity benefited from the recirculation. The reactor exhibited an increase in overall COD removal efficiency of 8% and a substantial decrease in effluent COD concentration of 30%. The results suggest that media pore size and porosity play a more significant role than media specific surface area in the performance of upflow APBRs.
Autotrophic denitrification of landfill leachate using elemental sulphur
Authors: Koenig A. , Liu L. H.
Published: May 2018

One of the most economical means of nitrogen removal from leachate is biological treatment by nitrification, followed by heterotrophic denitrification. An alternative biological denitrification process is autotrophic denitrification using Thiobacillus denitrificans. This autotrophic bacteria oxidizes elemental sulphur to sulphate while reducing nitrate to elemental nitrogen gas, thereby eliminating the need for addition of organic carbon compounds. For this study, pilot-scale elemental sulphur packed bed columns with fixed-film denitrification have been selected as the most suitable treatment process. The effect of hydraulic retention time as well as the effect of concentration and loading rate of nitrate on nitrate removal efficiency as a function of sulphur particle size were determined. The results indicate that (i) autotrophic denitrification can effectively remove nitrate from synthetic and actual nitrified leachate at concentrations much higher than hitherto reported; (ii) the minimum hydraulic retention time necessary for complete denitrification depends on sulphur particle size; (iii) the maximum area loading rate, in g NO3−-N/m2·d, appears to be the process limiting factor and is practically independent of sulphur particle size; and (iv) the observed stoichiometric relationships compare well with those previously reported.
Complete anaerobic digestion of activated sludge by combining membrane separation and alkaline heat post-treatment
Authors: Takashima M. , Kudoh Y. , Tabata N.
Published: May 2018

The objective of this laboratory study was to improve the particulate solids decomposition of activated sludge by combining solids-liquid separation and post-treatment to anaerobic digestion. The application of membrane separation has been shown to enhance the anaerobic biodegradability of sewage sludge. In this study, an anaerobic membrane digester with a volume of 51 and UF membrane of 177 cm2 was operated at 35 °C and a HRT of 30 days without considerable sludge wastage. For the first 83 days, the membrane digester was operated without post-treatment. For the succeeding 41 days the membrane digester was combined with alkaline heat post-treatment. This was done by taking out 50 ml per day of the digester sludge, post-treating it under the condition of 0.1M NaOH and 175 °C for 1hr, and returning it to the digester. The particulate solids decomposition percentage averaged for each operating phase was 61% without the post-treatment and about 100% with the post-treatment. These results indicate that the post-treatment was able to selectively destroy unbiodegradable components of the lab-cultivated activated sludge. In addition, because the feed activated sludge can be concentrated in the membrane digester, the post-treatment requires less volume to be treated than pre-treatment. On the other hands, the operation and application of this post-treatment combined process are limited by the allowable digester sludge level imposed by the membrane separation. The problem to be solved is the deterioration of membrane permeate quality and methane production efficiency.
Selective determination of non-biodegradable polar, organic pollutants in waste water related to functional groups using flow injection combined with tandem mass spectrometry
Authors: Schröder H. Fr.
Published: May 2018

Effluents of biological sewage treatment plants mainly contain non-biodegradable, polar, organic pollutants of biogenic and anthropogenic origin. This paper presents a substance-specific determination method for these compounds, which are partly able to reach drinking water during the soil filtration process. Tandem mass spectrometry (MS/MS) combined with softly ionizing interfaces is applied for this purpose. The behaviour of the functional groups of these pollutants - forming characteristic fragment ions under MS/MS conditions and abstracting neutral particles - is used for detection. With help from this screening process on specific functional groups it is possible to establish the presence of substance groups with similar behaviour in the aquatic environment. Additionally this analytical procedure provides information on the molar mass of the pollutants detected. In a second step the compounds characterized by the molar mass and belonging to a group of pollutants with specific functional groups can be identified using MS/MS.
Kinetics of halogen substituted aniline transformation in anaerobic estuarine sediment
Authors: Susarla Sridhar , Masunaga Shigeki , Yonezawa Yoshitaka
Published: May 2018

The kinetics of halogen substituted anilines were examined in estuarine sediment collected from Tsurumi river, Japan. Aniline was substituted with F, Cl, Br and I groups at meta or para positions on the aromatic ring. The transformation of all the compounds followed a first-order reaction kinetics with rate constants for the disappearance ranging between 0.002 to 0.006 day−1 or half lives between 108 and 669 days. Results indicated that para substituted anilines transformed two to four times faster compared to meta substituted ones. The rate of transformation followed the order: I > Br > Cl > F. A quantitative structure-activity relationship was evaluated relating the first-order rate constant in sediment with several readily available molecular descriptors: carbon-halogen bond strength, Hammett sigma constants, Taft steric constant, and Lipophilic constant. In addition octanol/water partition coefficients and solubility were included in the correlation. The relationship obtained was only significant between the rate constant and lipophilic constant.
Use of the freshwater macroinvertebrate Chironomus riparius (diptera: chironomidae) in the assessment of sediment toxicity
Authors: Watts M. M. , Pascoe D.
Published: May 2018

The growth and emergence responses of the midge Chironomus riparius Meigen were used to evaluate the toxicity of natural and formulated reference sediments which were either obtained from polluted sites or spiked with copper in the laboratory. A significant reduction in larval growth was only observed in one of the two polluted field sediments tested. The reasons for this are discussed. However, copper spiking resulted in significant growth reductions of larvae exposed to the two formulated reference sediments at copper concentrations of 3 and 4 mg Cu2+ 1−1. Growth of larvae exposed in natural reference sediment was not significantly affected at equivalent concentrations.

The emergence of adults was adversely affected in polluted field sediment compared to formulated reference sediment. Male, female and total adult median emergence times (EmT50) were significantly greater in the former treatment indicating a delay in emergence, attributable to sediment contamination. In addition, survivorship of the larvae in the polluted sediment was reduced, resulting in a lower percentage of adults emerging compared to the formulated reference sediment. The results of this study illustrate the usefulness of chronic response criteria, incorporating the more sensitive life-stages of C. riparius, in the assessment of sediment toxicity.
Antimony in the aquatic environment in north Kyushu district of Japan
Authors: Nakamura Yuko , Tokunaga Takashi
Published: May 2018

In Japan, the water quality standards for items requiring surveillance for drinking water in 1992 and environmental water in 1993 stipulate that the concentration of antimony is 2 μg/l or less. Recently cases of water contamination by antimony have been reported throughout Japan. We have measured antimony concentrations in the aquatic environment in north Kyushu district of Japan by atomic absorption spectrometry with hydride generation and found them to be in the range 0.0 to 0.8 μg/l all of which were less than the water quality standards at the present time. However, wastewater containing high concentration of antimony may contaminate aquatic environment in future. Studies have since been carried out to remove antimony from polluted wastewater. We tried to use ferric chloride as coagulant and dechlorination tap water containing approximately 10 μg/l antimony as the sample solution. Of the sample solution, pH of which was 7 - 8 and included the ferric chloride, pH was controlled by adding either hydrochloric acid or sodium hydroxide. The efficiency of removal of antimony reached a maximum at pH 4.0 - 5.5. When ferric chloride concentration was more than 30 mg/l at pH 4.5, 80 - 90% antimony was removed. However, when the original antimony concentration was 250 μg/l, up to 200 mg/l ferric chloride had to be added. Therefore, from water originally polluted by antimony at concentrations of 2 - 250 μg/l, almost complete removal of antimony is expected by adding ferric chloride to become 200 mg/l and adjusting the pH to 4.5.
Impact assessment of industrial and municipal effluents on surface water - a case study
Authors: Zagorc-Koncan Jana , Cotman Magda
Published: May 2018

Surface waters are used for disposal of industrial and municipal effluents. The regulations limit effluent concentrations of contaminants to protect rivers and their biota. Only low concentrations of various contaminants are usually found in treated effluents but they have often been accumulated over time in sediments. Sediment quality investigations are necessary beside water quality determination for assessment of harmful impacts of discharges on the river.

The quality evaluation of Krka river was used as a case study for assessment of the impact of effluents from both industrial and municipal wastewater treatment plants. The evaluation of the impact of treated wastewaters on the river is based on chemical analysis of river water, sediment, sediment elutriates and pore water (COD, BOD, nutrients and metals) as well as toxicity measurements of river water and sediment elutriates. Sediment elutriates were prepared by natural leaching process simulation. By comparative investigations upstream and downstream from the wastewaters' discharges the influence of pollution upon the Krka river was studied.
Determination of polychlorinated biphenyls and polyaromatic hydrocarbons in frog liver
Authors: Vojinovic-Miloradov Mirjana , Buzarov Danica , Adamov Jasna , Simic Smiljka , Popovic Ester
Published: May 2018

The aim of this work was to determine the content of the residues of the most commonly detected organohalogens and polychlorinated biphenyls in biomaterial. It is also the introduction of frogs as a new fine indicator of pollution in aquatic and terrestrial systems, due to their abundance all over Europe and their habitats in still and running waters. The residues of organohalogens and polyaromatic hydrocarbons in frog liver samples were taken from four sites - the river Danube and canal DTD in Vojvodina (northern part of Serbia), from the river Dubasnica near the town of Bor and in the Zlot canyon, Serbia, Yugoslavia. They were determined using gas chromatography with mass detector (GC/MS) and they indicate the high level of contamination of the chosen aquatic and terrestrial ecosystems by HCH, PCB, PAH and herbicides.
Post-Gulf War assessment of the levels of PAHs in the sediments from Shuaiba Industrial Area, Kuwait
Authors: Saeed Talat , Al-Muzaini Saleh , Al-Bloushi Amal
Published: May 2018

Kuwait's marine environment was heavily impacted by the events following the Gulf War of 1991. A large spill originated in the area close to Shuaiba Industrial Area which was already polluted as a result of oil-related and industrial activities. The objective of this study was to assess the status of the marine sediments from this area for petroleum-related pollutants. The sediment samples were collected over a one year period from seven locations and were analyzed for their PAH contents. The results indicated that the samples of the first batch were relatively highly contaminated. The levels of PAHs showed a downward trend in the subsequent batches. Higher molecular weight PAHs constituted the bulk in most of the samples. The levels encountered were considerably higher than those reported for the samples collected from the same general area prior to the Gulf War.
Control of algal growth by macrophytes and macrophyte-extracted bioactive compounds
Authors: Nakai Satoshi , Hosomi Masaaki , Okada Mitumasa , Murakami Akihiko
Published: May 2018

Algae (Selenastrum capricornutum and Microcystis aeruginosa) were respectively assayed in a mixed-culture system using various concentrations of macrophytes obtained from Egeria densa, Cabomba caroliniana, and Myriophyllum spicatum in order to evaluate their inhibitory effects on algal growth due to possible secretion of anti-algal bioactive compounds under coexistence conditions. Based on this methodology, we also evaluated the methanol extract from macrophyte tissues, their extract fractions from a polarity-based fractionation process, and the biodegraded filtrate from the most inhibitory fraction of each macrophyte at an initial concentration which was quantitatively confirmed to produce strong inhibition of algal growth, although in this case, heterotrophic bacteria was also added to the assays. Algal assays investigating coexistence showed clear inhibitory effects which confirm the secretion theory, and also indicated the occurrence of a species-specific reaction. In these assays, and in those using the methanol extract fractions, M. spicatum demonstrated the strongest inhibitory effects on both algae. The extract fraction assays showed that in all cases the fraction containing the highest polarized compounds was the most inhibitory one, while the examined filtrates showed rapid biodegradation of all their anti-algal bioactive compounds in parallel with a substantial increase in biomass of heterotrophic bacteria.
Effect of anionic and nonionic surfactants on sorption and micellar solubilization of monocyclic aromatic compounds
Authors: Doong Ruey-an , Lei Wen-gang , Chen Tsu-feng , Lee Chen-yeu , Chen Jee-hua , Chang Wen-heui
Published: May 2018

The effect of anionic and nonionic surfactants on the sorption and micellar solubilization of monocyclic aromatic compounds in soil-free and soil-water systems was investigated at 25 °C to examine the feasibility of in situ remediation. Benzene, chlorobenzene and styrene (BCS) were selected as the target compounds due to their suspected carcinogenic and mutagenic properties. Sodium dodecyl sulfate (SDS) and Triton X-100 were used to represent the anionic and nonionic surfactants, respectively. The addition of Triton X-100 had little effect on the micellar solubilization of BCS. However, the solubilization of aromatic compounds increased significantly with the increase of SDS concentration. A 20% to 43% enhancement of the solubilization in SDS-amended systems was demonstrated. The adsorption isotherms of BCS with Triton X-100 can conveniently be fitted by Langmuirian expression. However, multilayer adsorption of chlorobenzene and styrene was observed in SDS-amended systems. The values of maximum adsorption capacity ranged from 323 to 736 μg/g. Also, the effect of Triton X-100 on maximum adsorption capacity was greater than that of SDS. Moreover, a correlation between the maximum sorption capacity and partition coefficient was established. The results of this study demonstrate that surfactants can be effectively used as chemical amendments to minimize the volatilities of monocyclic aromatic compounds and enhance sorption and solubilization in soil environments contaminated by proper selection of surfactant type and concentration.
Disinfection by-products formation during hypochlorination of isoproturon contaminated groundwater
Authors: Lopez A. , Mascolo G. , Földényi R. , Passino R.
Published: May 2018

An investigation has been carried out to identify the by-products formed during the disinfection by hypochlorite of water contaminated with isoproturon, one of the herbicides most used in Europe. The reaction of isoproturon with sodium hypochlorite (NaCIO) has been investigated in synthetic aqueous solutions, over 48h, in presence and in absence of interfering bromide ions, at room temperature, within the pH range 6-9, using two different (NaCIO)/(isoproturon) mass ratios: (40ppm)/(10ppm) and (3ppm)/(10ppb). When the effect of bromide ions was studied, (NaCIO):(Isoproturon):(Bromide) mass ratios were (40ppm):(10ppm):(20ppm) and (3ppm):(10ppb):(100ppb). By-products were detected by liquid chromatography and identified by HPLC-MS and GC-MS. The results indicated that: the higher the reagent concentrations the faster the reaction, the presence of bromides speeds up the reaction, pH does not influence the reaction, four and three identified isoproturon substitution by-products are formed in the absence and in the presence of bromides respectively.
Laboratory study on dispersion prevention of dissolved sexivalent chromium in groundwater by cement-bentonite cut-off barriers
Authors: Kashiwaya Mamoru , Deguchi Hiroshi , Ueoka Seiichi , Iwaasa Hiromu , Iio Masatoshi
Published: May 2018

Laboratory permeability tests with soft groundwater contaminated by Cr6+ were carried out to develop measures to prevent dispersion of Cr6+ concentrate into a large amount of groundwater by providing cut-off barriers made from a mixture of blast furnace slag cement and sodium type bentonite. From these tests, it was necessary to maintain the permeability coefficient of 3×10−9 m/sec. or lower as soon as possible after the barrier provision. Through a test in which MgCl2 of 270 mg/L and some amounts of Ca(OH)2 for pH adjustment were added to the permeating Cr6+ groundwater, it was found that for the pH to be adjusted within a range of 9.0 to 9.5 was an appropriate approach. Through the other test in which MgCl2 of 270 mg/L and some amounts of either poly-aluminium chloride(PAC) or Al2(SO4)3 were added to the permeating Cr6+ groundwater, it was also found that the addition of PAC brings a good result due to the reduction of permeability and no breakthrough of Cr6+ containing leachate. It was confirmed that the minimum requirement of pAC was 30 mg/L as Al2O3.
Use of post-consumer carpet products during landfill management of solid wastes
Authors: Pohland F. G. , Rachdawong P.
Published: May 2018

This report focuses on the potential for using waste carpets as part of cover and liner systems at municipal solid waste landfills. Five different carpet materials were tested for their characteristics before and after incorporation with solid wastes in simulated landfill bioreactors. Selected analyses are presented on heavy metals and volatile organic compounds from TCLP extracts, and on leachate and gas samples during operation with and without leachate recycle. Biological clogging tests indicated no alteration in carpet integrity o2r significant reduction in permeability. Solid waste stabilization, indicated by gas and leachate parameters, proceeded without adverse impact from the codisposed carpets. Volatile organic compounds and heavy metals were present in trace amounts and below regulatory limits. These results supported post-consumer use of carpets as filter and separation layers for municipal solid waste landfill cover and liner systems.
A retrospective assessment of water reclamation projects
Authors: Mills Richard A. , Asano Takashi
Published: May 2018

Stimulated by droughts and inability to construct new freshwater projects, water suppliers in California, U.S.A. have taken a heightened interest in water reclamation in the last decade. Since 1980 the California State Water Resources Control Board has approved financial assistance to local water supply agencies to design and construct water reclamation facilities. Nineteen of these are now operating. There is an opportunity to assess how well projects are performing in relation to their planned objectives, in particular, deliveries of reclaimed water to users. Based on reports on many of these projects, it is found that two-thirds of the projects are delivering 75 percent or less of the expected amounts of water. Data are provided on project performance. A discussion is provided of the problems encountered on many of the projects that account for these deficiencies in yields and have caused other problems in implementation.
Effluent reuse options in Athens metropolitan area: A case study
Authors: Tselentis Yiannis , Alexopoulou Stella
Published: May 2018

In the Athens Metropolitan area nearly 700,000 m3 of effluent is produced per day which after its primary treatment is being discharged into the sea. A serious concern has been expressed by local municipalities and the government on wasting a valuable potential resource. An integrated approach has been selected, which takes into account the water resources management aspects, the growing population and the increasing demand for improving the environmental standards in the greater Athens area. The methodology developed includes: the geographical distribution of prospective users, the quantities required and the availability and cost of the existing sources, the quality standards required and the treatment needed per use, the associated public health and environmental hazards, the institutional and political aspects, the monitoring and control requirements, the social awareness and the need for education and public acceptance for effluent reuse. The various uses examined include: crop irrigation, irrigation of afforestated areas, industrial water supply and domestic non potable use. Twelve different reuse schemes were evaluated. The conclusions are of great interest, since the quantities of the available effluent are enormous and allow the development of an overall reuse strategy for a typical Mediterranean metropolitan area like Athens.
Simulation of groundwater recharge with advanced treated wastewater
Authors: Drewes Joerg E. , Jekel Martin
Published: May 2018

Although the quality of the effluents of domestic wastewater treatment plants in Germany is better than in the past, there are still problems using it for groundwater recharge. The problems are caused by substances, which are not or only poorly degradable in the wastewater treatment facility. They can be described by the parameters dissolved organic carbon (DOC) and adsorbable organic halogens (AOX). In a laboratory plant for the simulation of groundwater recharge with advanced treated domestic effluent, various soils were used to differentiate between sorption and biodegradation. Using aquifer material, DOC-reduction by biodegradation was 23 % under aerobic conditions, and 35 % under anaerobic conditions. Under aerobic conditions AOX was degraded by 16 % and under anaerobic conditions by 22 %, based on a special cometabolism. Further examinations showed that 60 - 80 % of the remaining DOC was not adsorbable by activated carbon used in drinking water facilities. The AOX in the effluent could be reduced by an activated carbon treatment (PAC) down to 23 μg/L, compared with 48 μg/L in the standard biological treatment. The subgroups AOCl, AOBr and AOI show a different behaviour, with the worst elimination of AOI under aerobic conditions. Nevertheless, after optimization of the modern treatment technologies, this reuse concept for wastewater could be realized in the Berlin region in a near future.
Developing human health-related chemical guidelines for reclaimed wastewater irrigation
Authors: Chang Andrew C. , Page Albert L. , Asano Takashi , Hespanhol Ivanildo
Published: May 2018

We examined the methodology of developing globally applicable human health-related chemical guidelines of using wastewater for crop irrigation. Two approaches may be used to develop pollutant loading guidelines: (a) preventing pollutant accumulation in waste receiving soil and (b) maximizing soil's capacity to assimilate, attenuate, and detoxify harmful chemicals. Pollutant loading rates based on the first approach are in agreement with the fundamental principle of maintaining ecological balances in soil. But numerical limits usually are very stringent and it is difficult for communities to meet these requirements. Recommendations derived with the second approach represent the maximum permissible loadings beyond which pollutant levels in the soil may be harmful to the exposed population. A method employing the second approach was evaluated. Preliminary pollutant loading limits for land application of wastewater are derived by considering the food chain transfer of pollutants via intake of grain, vegetable, root/tuber, and fruit grown on wastewater-affected soils.
Toluene removal in a biofilm reactor for waste gas treatment
Authors: Pedersen Anne R. , Arvin Erik
Published: May 2018

A lab-scale trickling filter for treatment of toluene-containing waste gas was investigated. The filter performance was investigated for various loads of toluene. Two levels of the gas flow were examined, 322 m d−1 and 707 m d−1. The gas inlet concentrations were varied in the range from 0.6 to 4.0 g m−3. The toluene elimination increased linearly with increasing load, and at maximum load the elimination was 50 g m−3 h−1 (70% purification efficiency). This was in accordance with reported values for toluene removal in trickling filters. The removal was determined by the gas/liquid mass transfer and the biological degradation as well. An analytical model described the toluene removal as a half-order removal by use of two sets of parameters for the gas/liquid mass transfer and the biological degradation due to the two different gas flows. The mass transfer coefficients and the surface removal rates estimated by parameter fitting corresponded to previously observed values. The effect of the gas flow on the mass transfer coefficient and the biological removal rate may be explained by different flow patterns of the gas and the liquid phases. A characterisation of the biofilm showed an almost even biofilm growth over the filter height, which was in accordance with a constant liquid concentration throughout the column.
Nitrous oxide production by nitrifying biofilms in a biofilm airlift suspension reactor
Authors: Garrido J. M. , Campos J. L. , Méndez R. , Lema J. M.
Published: May 2018

A nitrifying biofilm airlift suspension (BAS) reactor was operated at an ammonia loading rate (ALR) of 5 kg N-NH4+/m3•d, obtaining ammonia conversions of 99%. Neither denitrification nor nitrous oxide production was detected when a suitable carbon source was not present in the system over a long experimental period. However, in the presence of organic matter coming from biofilm hydrolysis or added in the influent nitrous oxide production was found. The addition of 55 mg/l formaldehyde to the influent produced rises in the nitrous oxide production of up to 2 kg N-N2O/m3•d. Nitrogen balance showed that nitrous oxide was the sole or major product of denitrification in the system.
Biofilm abrasion by particle collisions in airlift reactors
Authors: Gjaltema A. , Vinke J. L. , van Loosdrecht M. C. M. , Heijnen J. J.
Published: May 2018

Biofilm development is determined by the balance between growth and detachment. The detachment of biomass from suspended biofilm pellets was investigated in three-phase internal loop airlift reactors under non-growth conditions, and in the presence of bare carrier particles. Particle collisions were found to dominate the detachment. These collisions caused an on-going abrasion of the biofilm pellets. The abrasion rate was linear with both the concentration of biofilm pellets and the bare carrier particles up to a solids hold-up of 30%. An increase in particle size drastically increased the abrasion rate. Carrier roughness also strongly influenced the detachment rate. Experimental results were interpreted in terms of collision frequency and collision impact, and could partly be described by conventional collision theory. Particle responses to flow fluctuations, the effect of carrier roughness and the effect of growth rate on biofilm strength and elasticity need to be included. Some consequences for reactor operation and start-up are discussed.
Biofilm structire and kinetics
Authors: Bishop Paul L.
Published: May 2018

Recently, conventional concepts concerning the internal structure of wastewater biofilms have been brought into question. Most existing biofilm kinetic models assume that biofilms can be modeled in a one-dimensional (perpendicular to the substratum) fashion. There is much evidence indicating that mature biofilms may adequately be considered as growing as a continuum, although heterogeneously stratified with depth, and thus can be modeled in this way. However, there is recent evidence indicating that at least some biofilms grow in a much more heterogeneous format, with a highly channelized structure. This paper reviews the research on biofilm structure and the implications for substrate and nutient mass transport into biofilms. It then discusses the impact of the various growth models on biodegradation kinetics.
A comparison of biofilm growth and water quality changes in sewers with anoxic and anaerobic (septic) conditions
Authors: Æsøy Anette , Storfjell Målfrid , Mellgren Lovisa , Helness Herman , Thorvaldsen Gøril , Ødegaard Hallvard , Bentzen Greta
Published: May 2018

Changes in water quality in sewers may have significant effects on the performance of treatment plants. Experiments have been carried out in two pilot scale sewers for studies of biofilm growth and changes of water quality with anoxic (dosage of nitrate) and anaerobic (septic) conditions, respectively. The thickness of the biofilm in the anoxic sewer was 1-2 mm as compared to 0.3-0.6 mm in the septic sewer at a water velocity of 0.5 m/s. An increase in the water velocity from 0.002 m/s to 0.5 m/s gave thicker and denser biofilms. Sulphide formation was prevented in the anoxic sewer, and influent sulphide was efficiently removed. The denitrification rate in the anoxic sewer was 3.5-4.3 g NO3-N/m2d (15°C). This gave a considerable reduction in both organic matter and phosphorus and an increase in pH and alkalinity. The potential to remove organic matter in sewers may be exploited as a pre-treatment to mechanical and chemical treatment plants in order to meet more stringent effluent standards for organic matter discharge. Removal of readily biodegradable organic matter in the sewer may, however, be a disadvantage for treatment plants based on pre-denitrification. A reduced phosphate concentration may give a reduced metal coagulant dose at chemical treatment plants, whereas an increase in pH and alkalinity may give an increased dose. In the septic sewer, there was a small reduction in the organic matter, but no significant net change in total phosphorus, pH and alkalinity on average. The production rate of sulphide was in the range of 0.3-0.7 gS/m2d (15°C). On average there was no change in the concentration of suspended solids in either of the sewers. A sporadic large sloughing of biofilm was observed, particularly in situations with a very diluted wastewater. Sporadic high concentrations of suspended solids may cause separation problems at treatment plants.
The fate of peroxyl radicals in aqueous solution
Authors: von Sonntag Clemens , Dowideit Peter , Xingwang Fang , Mertens Ralf , Xianming Pan , Schuchmann Man Nien , Schuchmann Heinz-Peter
Published: May 2018

The reactions of peroxyl radicals occupy a central role in oxidative degradation. Under the term Advanced Oxidation Processes in drinking-water and wastewater processing, procedures are summarized that are based on the formation and high reactivity of the OH radical. These react with organic matter (DOC). With O2, the resulting carbon-centered radicals O2 give rise to the corresponding peroxyl radicals. This reaction is irreversible in most cases. An exception is hydroxycyclohexadienyl radicals which are formed from aromatic compounds, where reversibility is observed even at room temperature. Peroxyl radicals with strongly electron-donating substituents eliminate O2.−, those with an OH-group in a-position HO2.. Otherwise organic peroxyl radicals decay bimolecularly. The tetroxides formed in the first step are very short-lived intermediates and decay by various pathways, leading to molecular products (alcohols, ketones, esters and acids, depending on the precursor), or to oxyl radicals, which either fragment by scission of a neighbouring C-C bond or, when they carry an a-hydrogen, undergo a (water-assisted) 1,2-H-shift.
Particle size distributions in treatment processes: theory and practice
Authors: Lawler Desmond F.
Published: May 2018

The removal of particles from water and wastewater streams is essential and is usually accomplished through flocculation, sedimentation, and filtration. Understanding particle removal requires understanding of particle heterodispersity, especially with respect to size. A joint mathematical and experimental approach to studying changes in size distributions in these processes has proven quite insightful. Recommendations for analysts and manufacturers of particle size distribution analyzers based on mathematical principles are elucidated. Flocculation modeling is quite advanced and can be used predictively under certain well defined conditions, but a full description of changes in the size distribution is not available for all conditions encountered. Insights from flocculation modeling in the last ten years might make significant design and operational differences in the next ten years. Filtration modeling is not as advanced, inasmuch as filtration is a far more complex treatment process, but size distribution measurements have increased understanding enormously, and modeling has enabled design and operational changes in common practice to be understood.
Coagulation as a structure-forming separation process in water and wastewater treatment
Authors: Dymaczewski Zbysław , Kempa Edward S. , Sozanski Marek M.
Published: May 2018

This paper presents the results of research on coagulation sludge properties in three waterworks. The investigation assumed: chemical composition, specific surface of coagulation structures, their sedimentation, gravity thickening and rheological parameters. The solid fraction of the examined structures consisted mostly of mineral substances, especially silica, aluminium and iron oxides. This composition is typical for most coagulation sludges formed in surface water treatment facilities. It has been determined, that the main factor determining structures properties is chemical composition of the solid fraction, mainly alum and iron oxides. Their presence in the sludge causes a high specific surface in coagulation structures, and significantly influences the rheological properties. It has been proved that non-Newtonian properties appear first in structures with the highest contents of alum and iron oxides, with limit concentrations of c. 1.5%. Investigations on sedimentation and gravitational thickening showed a high stability of coagulation structures vs. forces. The water amount in the investigated sludges during their compression was no lower than 94-98%, which means that gravitational forces did not destroy these structures. The factors stabilizing coagulation sludges are; fine dispersion of the solid phase and high affinity to water molecules. This is why in the range of hydrations lower than the compression hydration, the coagulation structures are classified as quasihomogenous systems consisting of two interpenetrating quasicontinuous media, which means; solution of liquid dispersed to colloidal and semicolloidal particles of the solid phase. They act on each other by intermolecular forces, which are the volume forces.
Algal cells and coagulation, flocculation and sedimentation processes
Authors: Pieterse A. J. H. , Cloot A.
Published: May 2018

Flocculation generally removes two classes of suspended particles during adsorption-coagulation, namely colloids (inorganic in nature) and bacterial and algal cells, colonies, and filaments (organic in nature). Different interaction mechanisms, i.e. hydrodynamic, electrical and electromagnetic, play important roles in the removal of algal and colloidal entities. Algal entities, however, show morphological characteristics (such as elongated shapes, arranged in cells, colonies and filaments, containing spines or able to change shape or to move with flagella) not shared by colloids, that will affect the flocculation of the algal cells. If algal cells are globally in equilibrium with themselves, it is possible that the negative surface charge of algal cells will be restored after charge neutralisation. In addition to Van der Waals forces, affecting the coagulation of colloidal and algal entities, the flocculation of algal entities may also be affected by gravitation forces (because of larger sized algal entities) and forces created in the immediate vicinity of the cells by metabolic processes such as photosynthesis and respiration.
Reaction mechanisms and kinetics of chemical pretreatment of bioresistant organic molecules by wet air oxidation
Authors: Mantzavinos D. , Hellenbrand R. , Livingston A. G. , Metcalfe I. S.
Published: May 2018

The partial wet air oxidation of aqueous solutions of p-coumaric acid and polyethylene glycol, two model organic pollutants typically found in wastewaters of agricultural origin and polymer-manufacturing respectively, has been investigated at temperatures from 373 K to 513 K and oxygen partial pressures from 0.2 MPa to 3 MPa. Reaction intermediates have been identified and their concentration profiles have been determined using liquid chromatography as the main analytical technique, and reaction mechanisms and pathways have been postulated. The impact of various heterogeneous catalysts, such as metal oxides and noble metals, on the kinetics and mechanisms of the reaction has also been studied. Conversion of these model compounds through various oxidation intermediates to end-products, such as carboxylic acids, could be easily achieved even under mild operating conditions, while further total oxidation proved to be difficult even under more severe conditions. Catalysts were found to be, in general, capable of increasing the rates of both partial and total uncatalysed oxidation. The stability of some of the catalysts used has also been studied with respect to metal leaching and deactivation. The implications for complete removal of bioresistant organic pollutants by partial wet oxidation followed by a biological treatment step are also discussed.
Photocatalytic oxidation of phenolic compounds in wastewater from oil shale treatment
Authors: Preis Sergei , Terentyeva Yelena , Rozkov Aleksei
Published: May 2018

Experimental research into the photooxidation of aqueous solutions and wastewaters containing phenolic compounds was undertaken. Titanium dioxide under near-UV irradiation was selected as a photocatalyst. Phenol, p-cresol, resorcinol and 5-methylresorcinol (5-MR) were chosen as model compounds for the experiments with synthetic phenolic solutions. The photooxidative treatment of phenolic solutions was found to be more effective in acidic and strongly alkaline media. No difference was found between shortwave and near-UV irradiation photooxidation abilities. Methylated phenolic substitutes (p-cresol, 5-MR) yield better to photooxidation than non-methylated compounds. The higher the irradiation intensity the lower the photooxidation efficiency. The results obtained from the experiments with model compounds were compared with the results of photooxidative purification of wastewaters produced from the thermal treatment of oil shale in Estonia. Being heavily polluted, the wastewater yields better to photooxidation when slightly diluted with potable water in a 3:1 ratio. Anatase, immobilised onto the surface of buoyant hollow glass microspheres, was less effective than when suspended in a slurry. The photooxidatively pre-treated wastewater showed better biodegradability and lower toxicity to bacteria than untreated wastewater.
The use of particle monitoring in the performance optimisation of conventional clarification and filtration processes
Authors: Standen G. , Insole P. J. , Shek K. J. , Irwin R. A.
Published: May 2018

The application of laser diffraction particle monitoring to the performance optimisation of a pilot clarifier and full-scale rapid gravity filters (RGF), operating on water supply works in Hampshire, is described. Furthermore the dosing of powdered activated carbon (PAC) into the works' clarifiers has been evaluated in terms of RGF performance. A costly proposal to install a third filter medium was subsequently abandoned when it was found that particle numbers in the filtered water were consistently below 1×102/ml.

Various combinations and doses of coagulants and flocculant aids, shown to give optimum particulates removal during intensive jar testing trials, were transferred to the pilot clarifier. Particle monitoring enabled a more accurate derivation of suitable blanket chemistry and optimum blanket heights than turbidity changes. Raw water turbidities were 10-15 NTU at start-up with corresponding counts beyond the upper limit of the particle monitor. An on-line dilution system was developed to overcome this problem. Latex bead (4.33 μm) and Lycopodium spore (4-5 μm) suspensions (about 1 × 109 particles) were injected into the pilot clarifier to assess the removal efficiency of Cryptosporidium-sized particles. Reductions of about 1.7 log and 2.6 log were achieved for the beads and spores, respectively. Particle distributions of various PAC's and a bentonite were obtained in order to assess their potential effects on the coagulation process during clarification. Bentonite was also beneficial as an on-line means of checking particle monitor response and calibration.

The works' filters achieved 1.5 to 2.0 log removals of 2-5 μm particles without media addition or operational changes. Combined clarification and filtration gave better particulates removal than two-stage microfiltration.
Reactor modelling in the photocatalytic oxidation of wastewater
Authors: Giménez Jaime , Curcó David , Marco Pilar
Published: May 2018

Two different experimental devices have been tested for the photocatalytic oxidation of phenol, by using TiO2 suspensions. At the laboratory level, experiments were carried out in microreactors with Xe lamps. At pilot plant scale, the experiments were done at the Plataforma Solar de Almería (PSA), Spain, by using a high concentrating radiation systems (Heliomans) and solar radiation. Both systems were characterized from the point of view of the radiation field. Kinetic experiments and radiation measurements showed that kinetics are first order with respect to the phenol concentration, and a linear dependence of the reaction rate on the square root of the photonic flow. Kinetic constants (k) were calculated for both systems considering only concentration-time data. Results indicate that k values obtained at the laboratory were ten times greater than these obtained at the PSA. However, results improve when the radiation entering and the radiation absorbed by the catalyst were considered. The fitting of concentration-radiation data drives to values of the kinetic constants more similar for both systems and for all the catalyst concentrations tested. Thus, these new constants can be useful for the change of scale.
A new photochemical reactor design for the treatment of absorbing solutions
Authors: Karpel Vel Leitner N. , Le Bras E. , Foucault E. , Bousgarbiès J.-L.
Published: May 2018

The recent developments in the field of Advanced Oxidation Processes (AOP) require improvements in reactor design. Indeed, light-induced procedures cannot be used for the removal of micropollutants in strong absorbing solutions. In this work, the technical design concept for mixing in a cylindrical reactor has been approached in a rational way for the treatment of compounds in highly absorbing solutions. The new photochemical reactor perfected in our laboratory consists of an annular reactor with one UV lamp in axial position. However, this reactor differs from classical ones since the rotation of the quartz sleeve protecting the lamp associated with the flux of the solution establishes a Couette-Taylor type flow. This means that toroïcal eddies are formed between the two surfaces of the cylindrical reactor and thus, periodically, each fraction of liquid comes near the UV source. Three photochemical processes with irradiation at 254 nm have been examined: direct photolysis, H2O2/UV and TiO2/UV for the removal of organic micropollutants such as atrazine and aliphatic acids in strongly absorbant solutions. Para-nitrophenol in the concentration range 1.0 to 2.3 mmol.L−1 (3.0-6.4 cm−1) has been added to the water to be treated as a product that absorbs the 254 nm light. The overall effect simulates that of an inner filter absorbing incident photons. In several experiments, para-nitrophenol was replaced by a mineral component bentonite. Experiments showed that under these experimental conditions, for the three photochemical systems, the yield of oxidation was significantly increased as a result of the rotating movement of the central cylinder. This new design will be able to improve the efficiency of commonly used industrial reactors.