bluuebunny/crossref_metadata_2025 huggingface dataset:
Decolorizing Dye Wastewater with Low Temperature Catalytic Oxidation
Authors: Pak Daewon , Chang Wonseok
Published: May 2018

Novel oxidation technology to decolorize dye wastewater was discussed and the feasibility of color removal with Fe/MgO catalyst fluidizing in a reactor under continuous flow was demonstrated at room temperature. In batch tests, the oxidation reaction of reactive and disperse dye with an oxidizing agent, hydrogen peroxide, in the presence of Fe/MgO catalyst was performed. Through the catalytic oxidation, dyes were oxidized to molecules with lower molecular weight and then mineralized based on TOC analysis. The influence of hydrogen peroxide and catalyst dosage on the catalytic oxidation rate was verified. The catalytic oxidation rate increased with increasing hydrogen peroxide and catalyst dosage. Fe/MgO catalyst fluidizing in the reactor operated at room temperature was tested to decolorize the wastewater from a dye manufacturing industry. In the fluidized bed reactor, the wastewater was completely decolorized and about 30% of COD removal was obtained during 30 days of operation. Organic matters were degraded and part of them mineralized by the catalytic oxidation. BOD/COD ratio of the effluent from the fluidized bed reactor was increased compared to that of the influent. After 30 days of operation, the effluent from the fluidized bed reactor started becoming yellowish. COD and residual hydrogen peroxide concentration in the effluent started to increase due to the catalyst losing its activity.
New Biology for Advanced Wastewater Treatment
Authors: Miserez K. , Philips S. , Verstraete W.
Published: May 2018

A number of new technologies for the advanced treatment of wastewater have recently been developed. The oxidative cometabolic transformation by methanotrophs and by nitrifiers represent new approaches in relation to organic carbon. The Biological Activated Carbon Oxidative Filters characterized by thin biofilms are also promising in that respect. Moreover, implementing genetically modified organisms with improved catabolic potential in advanced water treatment comes into perspective. For very refractory effluents chemical support techniques, like e.g. strong chemical oxidation, can be lined up with advanced biology.
Phosphorus and Nitrogen Removal in Moving-Bed Sequencing Batch Biofilm Reactors
Authors: Pastorelli Giuseppe , Canziani Roberto , Pedrazzi Luca , Rozzi Alberto
Published: May 2018

A pilot moving-bed sequencing batch biofilm reactor (MBSBBR) fed with primary settled wastewater, was used in order to study organic carbon, phosphorus and nitrogen removal with and without external carbon sources. Patented KMT® polyethylene biofilm carriers were used. Organic carbon uptake and phosphorus release has been achieved in the anaerobic phase of the cycle, while nitrification, simultaneous denitrification (i.e., anoxic respiration of sequestered COD in the inner layer of the biofilm) and phosphorus uptake was observed in the aerobic phase. A stable biological phosphorus removal could be achieved only with an external carbon source. Since the process proved flexible and reliable, it is suitable for full scale application to municipal wastewater treatment plants (WWTPs), in order to meet EU total nitrogen and phosphorus limit values for discharge into sensitive receiving waters.
Simultaneous Nitrification-Denitrification Processes in Activated Sludge Plants: Performance and Applicability
Authors: Collivignarelli C. , Bertanza G.
Published: May 2018

This paper deals with the development of technologies aimed to upgrade existing waste water treatment plants, paying attention to high process efficiencies and low costs. We established conditions for good N removal efficiencies in extended aeration activated sludge plants which are not equipped with specific denitrification steps. The experimental process is based on establishing conditions in the biological reactor which allow simultaneous nitrification and denitrification without alternating (in time or in space) anoxic and aerobic phases; the aeration system is controlled by means of dissolved oxygen and/or redox potential measurements. The research was carried out on two real plants (design size: 2,500 p.e. and 440,000 p.e. respectively). The main advantages of this process (even if some aspects are still under investigation) are: total N removal efficiencies similar to a pre-denitrification process, without the need for an anoxic basin and decrease of operating costs (savings in electric energy consumption in particular) due to the low oxygen concentration required in the biological reactor.
Advanced Wastewater Disinfection Technologies: State of the Art and Perspectives
Authors: Lazarova V. , Savoye P. , Janex M. L. , Blatchley E. R. , Pommepuy M.
Published: May 2018

Chlorination/dechlorination and advanced disinfection processes (UV irradiation, ozonation, membrane filtration) have been reviewed in terms of their efficiency, regrowth potential, design parameters, experimental set-up, scale-up and industrial experiences. Existing results show the great influence of water quality, in particular of suspended matter concentration and organic content.

The efficiency and reliability of these processes are evaluated for different reuse applications. The critical analysis of the literature data and experimental results highlights UV irradiation as an effective and competitive advanced disinfection process. Ozonation is a viable solution in case of higher requirements for water quality including virus and protozoa removal. Ultrafiltration is a highly efficient process producing an excellent quality and totally disinfected effluent, particularly recommended for groundwater recharge and potable wastewater reuse. The choice between these advanced disinfection technologies depends on wastewater quality, existing standards, specific reuse applications and wastewater treatment work capacity.
Advanced Treatment and Disinfection for Municipal Wastewater Reuse in Agriculture
Authors: Liberti L. , Notarnicola M.
Published: May 2018

In a 3-year joint research project, approved in 1995 by the European Commission, methods for advanced treatment and disinfection of municipal wastewater to permit reuse in agriculture were investigated. Pathogen inactivation, disinfection by-products (DBP) formation and the cost effectiveness of disinfection methods involving UV rays, ozone (O3) and peracetic acid (PAA) were evaluated. The investigation was carried out on municipal effluents which had received different degrees of treatment (secondary, clarified, clarified-filtered) in a 100 m3/h pilot plant that was designed, built and operated at West Bari (S. Italy) municipal wastewater treatment plant. Under the experimental conditions investigated, the WHO microbial guideline for unrestricted reuse of wastewater in agriculture (1,000 CFU/100ml for Faecal Coliforms) was easily achieved with all three disinfectants, while the corresponding Italian standard (2 CFU/100ml) was effectively met only with UV at an O&M cost in the range 17.5-35 EURO/1000m3. Log-inactivation values ≥ 5 for both UV and PAA and ≥ 3 for O3 were obtained; selected pathogens were affected by UV and, in part, by O3. No DBPs were detected with UV and PAA, while limited formation of aldehydes was found with O3.
Treatment of Trace Organic Compounds by Membrane Processes: At the Lake Arrowhead Water Reuse Pilot Plant
Authors: Levine Bruno B. , Madireddi Kapal , Lazarova Valentina , Stenstrom Michael K. , Suffet Mel
Published: May 2018

Organic and trace organic performance data for ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) at the Lake Arrowhead water reclamation pilot plant are analyzed to determine the treatment efficiency of these processes in an indirect potable reuse design. Four organic parameters were studied: dissolved organic carbon (DOC), ultra-violet absorbance at 254 nm (UV-254), SUVA and base neutral analysis (BNA).

UF and NF removed the larger compounds from the influent, but had no significant impact on the base neutral fraction with the exception of sterols. The RO process removed DOC and UV-absorbance compounds from the effluent to their respective detection limits. Base neutral compounds were significantly removed by RO, leaving at extremely low concentrations small molecular weight compounds, indicating indirect potable reuse is technically feasible.
The Jeezrael Valley Project for Wastewater Reclamation and Reuse, Israel
Authors: Friedler Eran
Published: May 2018

The Jeezrael Valley is one of the richest agricultural regions of Israel, with urban communities in and around the valley. Irrigation in the valley follows the general trend of irrigation in Israel, where potable water is replaced by reclaimed wastewater. In the near future, reclaimed effluent is expected to form 80% of all irrigation water used in valley. This paper discusses a new regional wastewater reclamation and reuse project in the Jeezrael Valley which takes advantage of the proximity of the urban communities to the cultivated areas. The project combines semi-intensive wastewater treatment plants situated near the urban areas with wastewater reservoirs situated in the rural areas. The rationale behind the scheme is discussed and the performance during the first year of operation is presented. During this first year this combined reclamation system was able to release effluent of high quality. The system is expected to release effluent of unrestricted irrigation quality when all its components are installed, enabling the reservoirs to be operated in a full sequential batch mode.
Removal of Reactive Dyes by Sorption/Complexation with Cucurbituril
Authors: Karcher S. , Kornmüller A. , Jekel M.
Published: May 2018

Color removal is an important task in textile wastewater treatment. Cucurbituril, a cyclic hexamer with internal hydrophobic cavity, has been studied as sorbent for removal of reactive dyes. Loadings as high as 1 g/g and more were obtained, making the method seem interesting for technical application. A minimum of 1 to 5 mmol/L calcium is needed for efficient sorption. However, salt concentrations of 100 mmol/L and above decrease sorption efficiency due to increased solubility of cucurbituril in salt solutions. The pH has little influence between 4 and 7.5, higher pH-values can result in decreased sorption. The salt influences are similar for most of the tested dyes whereas the pH-effect differs from dye to dye.
Water resource quality policy: the approach adopted by the department of water affairs and forestry under the water law principles
Authors: Harris J. , van Vliet H. R. , MacKay H. M.
Published: May 2018

An intensive review of existing Water Law has just been conducted by the Department of Water Affairs and Forestry. The review was motivated by the need for preparation for new legislation to support water resource management with a goal of “some for all, forever.” The development of a water resource protection policy was begun in that review. This paper describes the major aspects of the policy at one point in a process of rapid development. Initial proposals are to use the concept of ecological integrity as an indicator of sustainable use of the resource. While management's goal is to ensure all water users will benefit from access to the water resource, ecological integrity provides a good indication of sustainability in the use of the resource. More discussion in this paper is, therefore, centred on ecological integrity than on individual water users under the assumption that the resource will only be able to provide for long term water uses if ecological integrity is assured. A water Reserve has been defined that is intended to protect water resources, so basic human needs can be met and ecological functions and processes can be sustained. Components of ecological integrity, that is, the chemical and physical characteristics of water, the quantity and assurance of water, the habitat (instream and riparian), and the structure and function of the associated biotic communities would be assessed through the use of a resource classification system. The approach integrates resource-directed measures for protection (such as resource quality objectives) with source-directed measures (such as effluent standards).
Assessment of complex industrial effluents in the netherlands using a whole effluent toxicity (or wet) approach
Authors: Tonkes Marcel , de Graaf Paul J. F. , Graansma Jannes
Published: May 2018

The assessment of Dutch waste water discharges or effluents is focused on the reduction of specific pollutants or substances. Many effluents in the Netherlands are of a complex nature though. Because of several limitations, an assessment of complex effluents is not possible by merely using a chemical specific approach. Examples are lack of analytical techniques, lack of ecotoxicological data and unknown combination processes. Therefore an additional approach is needed. The Whole Effluent Toxicity or WET approach has been introduced to overcome the mentioned limitations. It focuses on acute toxicity. In 1994 a pilot study was initiated in order to try out, adjust and evaluate the WET approach. The aims were to gain more insight in the occurrence of acute toxicity in complex effluents, and to try and prove the additional value of the approach. The study was performed with 17 different industrial effluents, consisting of 6 industrial branches. All effluents were tested with four different organisms. The results showed acute toxicity for at least one organism in 15 out of 17 effluents. In 8 cases the toxicity of the effluents could not be explained by using physical and chemical data. The results clearly show that the use of acute toxicity tests produces valuable, and especially additional, information.
Toxicity evaluation of wastewater from the pharmaceutical industry to aquatic organisms
Authors: Tišler Tatjana , Zagorc-Končan Jana
Published: May 2018

The aim of our research was to evaluate the acute and chronic toxicity of wastewater from the pharmaceutical industry to some aquatic organisms. The toxicity of three 24h proportional samples of wastewater was determined with the acute toxicity tests using the bacterium Vibrio fischeri and daphnid Daphnia magna. The inhibition of bacterial luminescence was measured after a 30 min exposure period and the immobility of daphnids was determined after 24 and 48h. The chronic effects on daphnid survival and reproduction were observed for three weeks.

The toxicity tests indicated that all investigated samples were acutely toxic to the organisms, but in each sample the responses of bacteria and daphnids were quite different. Acute and chronic effects on daphnids were observed when testing the first sample of wastewater, but no influence on bacteria was determined. The second sample was acutely toxic to both organisms. The third sample was toxic only to bacteria, while no influence on daphnid survival and reproduction was found. The reason for the different toxicity of the samples lay in their compositions. The comparison between chemical analyses and toxicity data showed that for daphnids the main cause of toxic effects was zinc.
Common pitfalls in the design and operation of membrane plants - or how I should have done it!
Authors: Brouckaert C. J. , Buckley C. A. , Jacobs E. P.
Published: May 2018

The authors, jointly and separately have been involved in various aspects of a number of membrane treatment plants: as researchers in laboratory and pilot scale investigations, as advisors in the design phase, and as consultants over operating problems or equipment failure. The major portion of this experience has been related to effluent treatment installations. In the course of these investigations we have observed (and sometimes perpetrated) a variety of situations which led to avoidable operating problems. This paper attempts to draw some general conclusions from these experiences, in the form of a set of guidelines, followed by some practical examples which highlight the relevance of some of the points which are raised.

Membrane separations have great potential in effluent treatment, but inherent in their power is their fragility. To harness the power, we have to protect the fragility from both chemical and mechanical abuse. In face of the uncertainties and contingencies of effluent treatment, this is a difficult task, and it is inevitable that progress will be accompanied by mistakes. It is essential that we assimilate and disseminate the information gained from these experiences.
Heavy meatals removal by a promising locally available aquatic plant, Najas graminea Del., in Taiwan
Authors: Lee Chon-Lin , Wang Tsen C. , Lin Ching-Ku , Mok Hin-Kiu
Published: May 2018

This study uses an aquatic plant, Najas graminea Del., to treat man-made wastewater containing single and/or binary components of copper, lead, cadmium and nickel. Adsorption experiments demonstrate that the adsorption process correspond to the Lagergren kinetic model with the rate constant close to 0.01 min−1; meanwhile, the equilibrium results corresponds to the Langmuir adsorption isotherm. Notably, the rate constants of metals are not significantly different between each other. Competitive effect on the adsorption kinetics of cadmium is insignificant with the background solute (lead) concentration up to 10 mg/l; while significant deviation observed with concentration of lead reached 100 mg/l. In addition, the maximum adsorption density of cadmium is reduced by around 50% in the presence of 100 mg/l of lead. A simulated copper plating wastewater is also treated by Najas graminea Del. to demonstrate its efficiency in removing metals from wastewater with multi-cations/anions.
Removal of refractory organics and color in pigment wastewater with Fenton oxidation
Authors: Park T. J. , Lee K. H. , Jung E. J. , Kim C. W.
Published: May 2018

This study was designed to evaluate (1) the removal of the non-biodegradable organics and color by Fenton's oxidation (2) the feasibility of Fenton's oxidation as a pretreatment or tertiary treatment following the activated sludge process in the pigment wastewater. The study was divided into two parts. The first part consisted of investigations on raw Yellow wastewater and Red wastewater, the second part was carried out on the final effluent from the existing extended aeration treatment plant. The batch test was conducted to determine the optimum conditions for plant operation such as pH, H2O2 dosage, molar ratio of Fe2+/H2O2 and contact time. It was found that the removal efficiencies of COD were 54.2%, 52.6% and 58.9%, the removal efficiencies of the color were 91.2%, 18.1% and 45.7%, for Red, Yellow Wastewater and Final Effluent, respectively. In the Yellow wastewater, BOD5COD ratio was not changed much after Fenton's oxidation, but in the case of the Red wastewater, BOD5COD ratio was increased from 0.04 to 0.36. Therefore Fenton's oxidation process is a very effective means for a pretreatment or tertiary treatment in the Pigment wastewater.
Occurrence of an environmental estrogen (4-nonylphenol) in sewage treatment plant effluent and the aquatic receiving environment
Authors: Sekela M. , Brewer R. , Moyle G. , Tuominen T.
Published: May 2018

The concentration of an environmental estrogen (4-nonylphenol) was determined in suspended solids and large volume water samples (501) collected from a major sewage treatment plant (STP) and two sites located on the lower Fraser River in British Columbia, Canada. The collection of suspended solids and large volume water samples was conducted concurrently using an in situ continuous flow centrifuge and solid phase extraction. The phase partitioning profile and log Koc of 4-nonylphenol were determined in the STP effluent and the Fraser River receiving environment. The data indicate the following: i) in situ continuous flow centrifugation and solid phase extraction techniques are appropriate methods for the determination of trace levels of 4-nonylphenol in suspended solids and water ii) the highest concentrations of 4-nonylphenol were measured in the STP final effluent iii) 4-nonylphenol showed preferential partitioning to the suspended solid phase in the STP effluent sample and iv) elevated levels of 4-nonylphenol were detected in the Fraser River receiving environment downstream of the STP.
Removal of CU2+, ZN2+ and PB2+ by adsorption onto fly ash and fly ash/lime mixing
Authors: Ricou P. , Lécuyer I. , Le Cloirec P.
Published: May 2018

Disposal of a growing amount of fly ash creates environmental problems due to the leachability of their heavy metal content. Elsewhere, desulfurization treatment in power plants induces pollution by their heavy metals. In this paper, removal of Cu, Zn and Pb by fly ash and fly ash/lime mixing was studied. In the first part of the study, isotherms at different pH were carried out at room temperature. Results show increasing removal with increasing pH. In the second part, experimental design methodology was used. The objectives were to determine the influential parameters among the seven studied for adsorption of copper, zinc and lead, then to study their interactions. Results indicate greater removal by using 100 g.l−1 of adsorbent with 20% mass of lime at pH 5. However, the preparation of the adsorbent must be modified to increase the role of lime in the removal mechanism.
Advanced treatment of dyeing wastewater for reuse
Authors: Li X. Z. , Zhao Y. G.
Published: May 2018

As one of the main pollution sources in Hong Kong, the textile dyeing and finishing industry creates a significant proportion of water pollution in nearby harbour zones. Generally speaking, conventional biological treatment processes have difficulties in degrading many dye chemicals causing high COD and colour in dyeing wastwaters. Studies using physical and chemical processes to further reduce COD and colour from dyeing wastewater have been intensively reported. The use of a photocatalytic process in the presence of TiO2 to degrade many different types of dye chemicals has been confirmed. However, how to efficiently separate and reuse TiO2 from treated wastewater became a notable problem in the application of a TiO2 photo-oxidation process. This study aims to develop an advanced treatment process for dyeing wastewater treatment. In which dyeing wastewater was initially treated by an Intermittently Decanted Extended Aeration (IDEA) reactor to initially remove those biodegradable matters and further treated by a TiO2 photocatalytic reactor as advanced treatment for complete decolorization and high COD removal. Suspended TiO2 powder used in photooxidation was separated from slurry by a membrane filter and recycled to the photoreactor continuously. The results demonstrated that photocatalytic-oxidation process could degrade those non-biodegradable organic substances in the effluent treated by the biological treatment process and also remove the colour from the effluent completely. TiO2, as catalyst, was successfully recovered by a membrane filter and continuously reused in the photoreactor. The quality of dyeing wastewater treated by the advanced treatment process can be good enough for reuse in the textile dyeing processes.
An ecological risk assessment for a South African acid mine drainage
Authors: Jooste Sebastian , Thirion Christa
Published: May 2018

Biotic integrity assessment of a stream subject to acid mine drainage (AMD) indicated that a number of the expected taxa were absent. Acute and chronic toxicity assessment of water sampled in a stream subject to AMD impact indicate that even at near neutral pH the metal concentration in the water dominates the toxicity toward Daphnia pulex. Extending the observation period to the death of test cohort in an otherwise standard sub-chronic toxicity test, allowed for generating a life table for the D. pulex. The probability of population extinction was estimated from the statistical characteristics of a bootstrap estimation of the dominant eigenvalue of a Leslie matrix based on the life table. At the current concentration levels of metals, notably manganese and zinc, in the water, a high risk to aquatic life exists. It is suggested that the metal content of the stream water also be addressed in an AMD water treatment plan.
Tailings as a source of environmental pollution
Authors: Licskó I. , Lois L. , Szebényi G.
Published: May 2018

The poorly recultivated tailings at the R. Ore Mines Co. site also contain large amounts of pyrite. Owing to oxidation and acidification processes triggered by oxygen-saturated acid rain, heavy metals are transported by the leachate via the groundwater to surface streams of high buffering capacity where the metals are precipitated within a brief period of time. The recipient Parádi Tarna is contaminated indirectly over the tributary Bikk stream. The solid metal compounds bonded to iron(III) hydroxide settle out over a short distance (a few km) in the bed of the Parádi Tarna. At times of low and medium streamflow the heavy metals impose no restriction on the use of Parádi Tarna water for irrigation. However, flood waves caused by periodic releases of temporarily stored mine drainage water, or by major rains stir up the, metal contaminated bottom sediment and transport it to the lower stream sections. In these periods the Parádi Tarna is unfit for irrigation.
Risk assessment using stochastic modeling of pollutant transport in landfill clay liners
Authors: Lo Irene M.-C. , Law Wendy K.-W. , Shen Helen M.
Published: May 2018

Risk assessment of landfil systems using Monte Carlo simulation in the prediction of groundwater contamination underneath a landfill insulated by clay liner is presented. The advantage of applying stochastic modeling is that uncertainties associated with various design parameters can be taken into account in the prediction of pollutant transport through the clay liner. A model based on a pollutant transport model considering advection, dispersion and sorption is developed in this study. The design parameters with their corresponding distribution forms are fed into the simulation model. The probability of the contaminant concentration in the groundwater underneath the landfill exceeding a predetermined value is used for risk assessment.
Biological assays for aquatic toxicity testing
Authors: Slabbert J. L. , Venter E. A.
Published: May 2018

A number of aquatic toxicity tests have been established for South African use, which include fish and Daphnia lethality tests, microbiotests, and short-term chronic tests. Studies on effluents and surface waters showed that all the tests have a viable role to play in water quality management. The most advantageous use of the tests is in battery form, so that tests can complement each other. The fish and Daphnia lethality tests, and algal growth inhibition test are recommended for regulatory and management purposes of effluents. If receiving water is used for drinking water purposes, the Ames Salmonella mutagenicity and toad embryo teratogenicity tests should be included in the battery of tests. Some of the rapid microbiotests, e.g. the protozoan oxygen uptake test, bacterial growth test and enzyme tests, could be valuable screening tools to identify and categorize toxic effluents.
Biodegradation studies as an important way to estimate the environmental fate of chemicals
Authors: Gotvajn Andreja Žgajnar , Zagorc-Končan Jana
Published: May 2018

Biodegradation is confirmed as an important mechanism of organic chemicals removal in natural systems. Estimation of biodegradability of chemicals which reach the aquatic environment in significant or even negligible quantities is necessary in assessing the entire hazard associated with their use. The aim of our study was to compare the standardized ready biodegradability assessment test (closed bottle test) and its modifications, employing the basic agreements on test principles of simulation of biodegradation in surface waters, yet no official standard method has been adopted. The standard test was modified using various natural river waters and a variety of nutrient conditions and microbial species trying to simulate the natural environment in the simplified way. Tests were performed with two compounds with different ability to degrade. Experiments indicate that predictability of biodegradation obtained by ready biodegradability assessment tests for surface waters in many cases is not reliable, because of different conditions, which may prevail in surface waters over time and affect biodegradation. However, the use of natural waters in screening tests assures additional information on fate of chemicals in rivers and lakes.
Controlling the Settling of Activated Sludge in Pulp and Paper Wastewater Treatment Plants
Authors: Clauss Frédéric , Balavoine Christel , Hélaine Delphine , Martin Gaëtan
Published: May 2018

Forest industry wastewaters are difficult to clean: hydraulic and organic load variations, filamentous bulking or pin-point flocs negatively impact depollution processes. The addition of a fine, mineral, talc-based powder, Aquatal, into the aeration tanks of wastewater treatment plants connected to pulp and paper factories has been successfully tested since end of '97. The first case-study presents full results obtained over a period of 18 months in a 20,000 p.e. plant connected to a paper factory. The mineral powder was regularly added to control sludge volume index, thereby ensuring low suspended solids concentration in the outfluent. Plant operators could easily adapt biomass concentration to match organic load variation, thereby maintaining pollution micro-organisms ratio constant. In a second case study, a trouble-shooting strategy was implemented to counteract filamentous bulking. A one-off, large dosage enabled the plant operator to deal effectively with poor settleability sludge and rapidly control sludge blanket expansion. In both cases, the main common characteristics observed were an increase in floc aggregation and the production of heavier and well-structured flocs. The sludge settling velocity increased and an efficient solid/liquid separation was obtained. After a few days, the mineral particles of Aquatal were progressively integrated into the sludge floc structure. When the mineral powder was added to the activated sludge in the aeration basin, chemical interactions frequently encountered with other wastewater treatment additives did not pose a problem. Moreover, with this mineral additive, the biological excess sludge displayed good thickening properties and dewatering was improved. Despite the addition of the insoluble mineral particles, the amount of wet sludge expelled did not increase. Aquatal offers a rapid solution to floc settleability problems which so frequently arise when physical or biological disorders appear in forest industry wastewater treatment plants.
Mechanisms of AOX Removal During Biological Treatment
Authors: Barton D. A. , Payne T. W.
Published: May 2018

It is well known that a portion of the AOX generated during the bleaching of chemical pulps will degrade to inorganic chloride when alkali and heat are added to the waste stream. As reported by others, this hydrolysis can potentially occur in the mill sewer system as well as within the wastewater treatment process. The present study was undertaken to examine the role which alkaline hydrolysis can be expected to play in the removal of AOX during biological treatment.

The results of these experiments indicate that, for the filtrates tested, (a) biodegradation can account for 75 percent of the total AOX removal across secondary treatment, where pretreatment of bleach plant filtrates is not provided, and (b) approximately forty percent of the AOX destroyed under harsh thermo-alkaline conditions is biodegradable AOX and approximately one-quarter of the AOX destroyed would be removed by alkaline hydrolysis in the secondary treatment process itself. This suggests that biological and thermoalkaline treatment processes target many of the same AOX components.
Performance evaluation of small treatment systems in Turkey
Authors: Akca L. , Samsunlu A.
Published: May 2018

In accordance with the development of tourism, sea pollution has become the major problem of the coastal zones. In order to realize sustainable touristic activities in Turkey, it is very important to treat wastewater and preserve the environmental quality. It is roughly estimated that there are around 2000 small treatment plants in Turkey. However, it is necessary to construct 10,000 more wastewater treatment plants to solve the wastewater problems in small settlements. In this study, performances of small treatment systems were investigated. Two types of the treatment plants were of concern. The first one is a continuous system based on fixed bed activated sludge process, whereas the second system is based on batch activated sludge process. 96 treatment plants have been investigated in this study. The wastewater characteristic is determined as strong domestic wastewater. It has been observed that the effluent quality of the batch activated sludge and aerated biofilter systems meet the discharge requirements of Water Pollution Control Regulation in Turkey. Furthermore, they would be easily adapted to meet the stringent standards that are proposed for sensitive zones.
Effect of long-term idle periods on the performance of sequencing batch reactors
Authors: Morgenroth E. , Obermayer A. , Arnold E. , Brühl A. , Wagner M. , Wilderer P.A.
Published: May 2018

Sludge storage can be used as an effective control handle to adjust plant capacity to large influent variations. The sequencing batch reactor (SBR) technology is well suited for temporary sludge storage because reactors can easily be switched off individually and operated in an idle mode. In this study experimental results on the effect of long term (weeks) idle periods on nitrogen removal are presented. The SBRs were operated with idle times ranging from 6 to 20 days. Batch experiments were performed where sludge was stored without the addition of any substrate for 7 weeks. In the SBRs, repeated long-term idle phases had only a minor effect on ammonia oxidation. The nitrite oxidation process was more sensitive to long idle phases resulting in temporary nitrite accumulation in the SBRs. Quantitative gene probe analyses demonstrated that the decay of ammonia oxidizers was slower than the decay of nitrite oxidizers which in turn decayed slower than heterotrophic bacteria.
Process and engineering improvements to rotating biological contactor design
Authors: Griffin P. , Findlay G.E.
Published: May 2018

The numerous process and operational advantages of using Rotating Biological Contactors to treat the flows of sewage from small communities are well documented, but more widespread adoption of the technology has been hindered by inadequate design and engineering which has led to excessive mechanical failures. The mechanical problems have tended to be interrelated with process requirements and both required addressing before a robust design able to achieve the required performance and 20 year asset life was achieved. The performance of plants with an improved rotor design (marketed as Bistar) is compared with plants with rotors by other manufacturers and found to be comparable. M+E costs have not been shown to increase as a result of more stringent specification. Other engineering problems including stormwater separation and division of small flows have also been addressed.
Environmental technology education in Portugal: analysis and perspectives
Authors: Brito A.G. , Melo L.F. , Santana F.
Published: May 2018

The scope of the present communication is the current status of environmental engineering in Portugal. The different approaches concerning the environmental engineering courses available at undergraduate levels as well as some post-graduation studies are described. Furthermore, an analysis based on strengths, weakness, opportunities and trend issues regarding the environmental engineering profession in Portugal is presented.
Microbial ecology of the leach bed anaerobic digestion of unsorted municipal solid waste
Authors: Silvey P. , Pullammanappallil P.C. , Blackall L. , Nichols P.
Published: May 2018

The microbial ecology of the sequential, leach-bed, mesophilic anaerobic digestion of unsorted, coarse municipal solid waste (MSW) was examined over 80 days. The methane yield was approximately 75% of the ultimate biochemical methane potential (BMP) of the waste loaded into the digesters. The operational strategy involved a sequence of two digesters containing fresh and anaerobically stabilised MSW respectively. Cell wall phospholipid fatty acid (PLFA) and ether lipid (PLEL) analysis was used to monitor changes in microbial biomass. Both Bacterial and Archaeal biomass were heavily influenced by pH during the two-week start up period. Archaeal biomass peaked just before the methane production rate reached a maximum whereas Bacterial biomass peaked at a later stage. Changes in the phylogenetic diversity of the population were monitored by denaturing gradient gel electrophoresis (DGGE). An analysis of the changes in DGGE banding patterns suggested that rapid start-up of a new reactor was effected byinoculation as well as the provision of buffering capacity from the mature reactor leachate.
Two-particle model of anaerobic solid state fermentation
Authors: Kalyuzhnyi S. , Veeken A. , Hamelers B.
Published: May 2018

A structured mathematical model of anaerobic solid state fermentation (ASSF) has been developed. Since a stable ASSF requires addition of significant quantities of methanogenic seed sludge and mass-transfer limitation becomes important, the model postulates the existence of two different types of particles inside the fermenting solid mass – so-called “seed” particles with low biodegradability and high methanogenic activity and so-called “waste” particles with high biodegradability and low methanogenic activity. Any particle is assumed to be a completely mixed reactor and mass transfer of solutes between the particles is brought about by diffusion. The model includes multiple-reaction stoichiometry, microbial growth kinetics, material balances, liquid-gas interactions and liquid phase equilibrium chemistry. The theoretical model agrees on the qualitative level with existing experimental studies of ASSF. Hypothetical computer simulations are presented to illustrate the influence of biodegradabilityand mass transfer intensity on the stability of ASSF. On this basis, possible measures are proposed to prevent accumulation of volatile fatty acids inside the “seed” particles beyond their assimilative methanogenic capacity.
Rheology of sludge from double phase anaerobic digestion of organic fraction of municipal solid waste
Authors: Battistoni P. , Pavan P. , Mata-Alvarez J. , Prisciandaro M. , Cecchi F.
Published: May 2018

In this paper experimental results on the anaerobic digestion of sewage sludge and organic fraction of municipal solid waste (OFMSW) by using a double phase process are reported. The long-term experiment has been carried out on a pilot scale plant, performed in different sets of operative conditions, during which granulometric distributions of particles in sludges and rheological properties of sludges were monitored. A significant fluidification of sludge was evidenced in the meso-thermo process, especially taking into account the variation in sludge behaviour from the first to the second phase. In the thermo-thermo process a fluidification higher than that shown in meso-thermo conditions is not observed, this suggesting that better results in terms of sludge conditioning can be obtained in a long time spent in thermophilic anaerobic digestion. Total volatile solids (TVS) and total fixed solids (TFS) become the most important parameters when mathematical modelling is applied to these processes.In the acidogenic phase, hydraulic retention time (HRT) and temperature are used to determine rigidity coefficient (RC), while only temperature is needed for yield stress (YC). Organic loading rate (OLR) and specific gas production (SGP) exert an important role in methanogenic phase description.
Performance of thermophilic semi-dry anaerobic digestion process changing the feed biodegradability
Authors: Pavan P. , Battistoni P. , Mata-Alvarez J. , Cecchi F.
Published: May 2018

The study concerns the application of the semi-dry single phase thermophilic anaerobic digestion process to the organic fraction of municipal solid waste. The xperiments were carried out using 3 m3 and 1 m3 CSTR pilot scale reactors. The process performance in terms of biogas yields, digester stability and kinetic spects was studied, considering a progressive increase in the feed biodegradability, in order to evaluate the process behaviour changing from an undifferentiated collection of waste to a separate collection. This was carried out using blends of two different kinds of substrates: mechanically sorted organic fraction of municipal solid wastes (MS-OFMSW) and source sorted organic fraction of municipal solid wastes (SS-OFMSW). The study shows that OLR up to 6 kgTVS/m3d can be applicable for the medium selected fraction (TVS/TS≤0.7), while for the MS-OFMSW alone this limit can be doubled. The results obtained with SS-OFMSW alone suggest the use of the double phase process to give more stable conditions.
Development of a methanogenic process to degrade exhaustively the organic fraction of municipal “grey waste” under thermophilic and hyperthermophilic conditions
Authors: Scherer P.A. , Vollmer G.-R. , Fakhouri T. , Martensen S.
Published: May 2018

Different laboratory-scale, continuously driven reactor concepts (up to 3 reactors in series, max. 70°C) for anaerobic digestion of the organic fraction of municipal grey waste were investigated. Over a period of 2½ years several setups of reactors being daily fed and held in steady state balance were investigated. The preferred variant was a 2-stage setup with a HRT of 4.3d for the 1st and 14.2d for the 2nd reactor.

Removal efficiencies of VS obtained by comparing the organic loading rate (OLR, g VS/l/d) of the effluent with the OLR of the feed could reach 80%. Removal efficiencies determined indirectly by the combined biogas yield of the 1st and 2nd reactor stage revealed even up to 91.5% of the theoretical possible yield of 807 l/kgVS. The produced gas had a methane content of 60–65%. A completely distinct hydrolysis stage with a gas production of only 1.6–5.5% of the theoretical yield could be reached by hyperthermophilic conditions (60–70°C) or by a HRT of 1.25d. It also demonstrated that a stable methanogenesis was not possible at temperatures of 60–70°C.

Kinetic analyses of the 2nd reactor stage revealed that the degradation of VS fell from 80 to 40% with raising organic loading rate (OLR) from 3 to 11 g VS/l/d. In contrast to this the VS-removal of the first hydrolysis reactor stage increased linearily from 5 to 20% at raising OLR's from 12 to 26 g VS/l/d. The same kinetics with linear increase exhibited the specific cellulose degradation with conversion rates of 0.1–3x109 g cellulose/single bacterium (10–12 g)/d. This was an indication for the cellulose degradation as a rate limiting step. Both reactor stages combined allowed an optimal VS removal efficiency at OLR of 10 g VS/l/d.

Analysis of bacterial populations of 28 reactors were referred either to eubacteria utilizing different sugars or cellulose or acetate or H2–CO2 or archaea (plus antibiotics) with acetate or H2–CO2 as substrate. H2–CO2 utilizers with numbers of 108–1010/g TS dominated obviously the acetotrophic methanogens by the factor 10–10,000. This explained the observed short HRTs being possible.
Influence of the size reduction of organic waste on their anaerobic digestion
Authors: Palmowski L.M. , Müller J.A.
Published: May 2018

The rate-limiting step in anaerobic digestion of organic solid waste is generally their hydrolysis. A size reduction of the particles and the resulting enlargement of the available specific surface can support the biological process in two ways. Firstly, in case of substrates with a high content of fibres and a low degradability, their comminution yields to an improved digester gas production. This leads to a decreased amount of residues to be disposed of and to an increased quantity of useful digester gas. The second effect of the particle size reduction observed with all the substrates but particularly with those of low degradability is a reduction of the technical digestion time. Furthermore, the particle size of organic waste has an influence on the dewaterability after codigestion with sewage sludge. The presence of organic waste residues improves the dewaterability measured as specific resistance to filtration but this positive effect is attenuated if the particle size of the solids is reduced.
Effects of disintegration on anaerobic degradation of sewage excess sludge in downflow stationary fixed film digesters
Authors: Engelhart M. , Krüger M. , Kopp J. , Dichtl N.
Published: May 2018

The effects of mechanical disintegration on anaerobic digestibility of sewage excess sludge in downflow stationary fixed film (DSFF) digesters were investigated on laboratory scale. Mechanical pretreatment using a high pressure homogenizer led to significantly enhanced concentrations of soluble proteins and carbohydrates in the feed sludge. Using DSFF digesters with two different tubular plastic media as support material it was shown that a stable digestion process could be achieved at hydraulic retention times (HRT) down to 5 days. Compared to conventional digesters at 10 d and 15 d HRT respectively, the degradation of volatile solids was enhanced up to 25%, also resulting in a higher specific biogas production. Further investigations on degradation of soluble proteins and carbohydrates showed that a slowly degradable fraction of carbohydrates was released via disintegration. Using the distribution of chain length and the concentrations of volatile fatty acids as process parameters, the dependability on the HRT and the degree of disintegration (the release of soluble COD) predominated the effects of specific surface area of the support media.
Anaerobic digestion technologies for closing the domestic water, carbon and nutrient cycles
Authors: Hammes F. , Kalogo Y. , Verstraete W.
Published: May 2018

Sustainable wastewater treatment requires that household wastewater is collected and treated separately from industrial wastewater and rainwater run-offs. This separate treatment is, however, still inadequate, as more than 70% of the nutrients and much of the chemical oxygen demand (COD) and potential pathogens of a domestic sewage system are confined to the few litres of black water (faeces, urine and toilet water). Whilst grey water can easily be filter treated and re-used for secondary household purposes, black water requires more intensive treatment due to its high COD and microbial (pathogens) content. Recently developed vacuum/dry toilets produce a nutrient rich semi-solid waste stream, which, with proper treatment, offers the possibility of nutrient, carbon, water and energy recovery. This study investigates the terrestrial applicability of Life Support System (LSS) concepts as a framework for future domestic waste management. The possibilities of treating black water together with other types of human-generated solid waste (biowastes/mixed wastes) in an anaerobic reactor system at thermophilic conditions, as well as some post treatment alternatives for product recovery and re-use, are considered. Energy can partially be recovered in the form of biogas produced during anaerobic digestion. The system is investigated in the form of theoretical mass balances, together with an assessment of the current feasibility of this technology and other post-treatment alternatives.