bluuebunny/crossref_metadata_2025 huggingface dataset:
Danube Field Excursion 1988: Tritium Content of River Water; Radioactivity of Danube Sediments
Authors: Rank D. , Maringer F. J. , Papesch W. , Rajner V.
Published: May 2018

Water, sediment, and fish samples were collected during the Danube excursion 1988, within a coordinated sampling program of the Radiology Working Group of the “Internationale Arbeitsgemeinschaft Donauforschung ” (K.Hübel, Munich; I. Kurcz, Budapest; D.Rank, Vienna). The H-3 content of the river water and the radioactivity of the bottom sediments were measured at the BVFA Arsenal, Vienna.

The determined H-3 content of the Danube water corresponds with the long-term trend in the H-3 content of the hydrosphere; the values lie in the range of 3 Bq/kg downstream from Belgrade, upstream from Belgrade they are about 4 Bq/kg. It was only in the waste water plume of the nuclear power station of Kozloduj that a slightly elevated H-3 value - 6 Bq/kg - was determined. The content of the sediments of artificial radionuclides was found, at the time of the Danube field excursion, to be almost exclusively due to the radioactive material released following the reactor accident at Chernobyl in April 1986 (mainly Cs-137 and Cs-134). As a consequence of the air currents and precipitation conditions prevailing at the time of the accident, the bottom sediments in the lower course of the Danube were less contaminated than those in the upper course. The fine sediments were found to contain over 3000 Bq/kg of Cs-137 in the upper course of the Danube.
The Radioactivity of Sediments in Danube Reservoirs in Austria before and after the Chernobyl Accident
Authors: Rank D. , Maringer F. J. , Terlunen J.
Published: May 2018

A major part of pollutants transported by rivers are normally adsorbed to the fine-grained particles in suspension. The coupling between pollutants and particles leads to an enrichment of radionuclides in sediments that settle in river reservoirs and lakes. The concentration of radionuclides is a function of grain-size distribution and of the mineralogical composition. In a survey, sediment samples from the lock area of each Danube reservoir were collected during the spring of 1985. Three grain-size fractions (<20 µm, 20–63 µm, 63–250 µm) were analyzed. On an average the estimated concentration of radionuclides is about 600 Bq/kg for K-40, 50 Bq/kg for Ra-226, and 40 Bq/kg for Th-232. A 17 m depth borehole has allowed us to trace the history of radionu-clide distribution for the past 25 years since the culmination and the end of atomic testing in the atmosphere, which coincides with the damming of the river Danube at Aschach. The content of Cs-137 in freshly deposited Danube sediments rose by two orders of magnitude following the accident at Chernobyl (i.e. up to 3000 Bq/kg).
A Complexation-Adsorption Model Describing the Influence of Dissolved Organic Matter on the Mobility of Hydrophobic Compounds in Groundwater
Authors: Lafrance P. , Banton O. , Campbell P. G. C. , Villeneuve J. P.
Published: May 2018

Natural dissolved organic matter found in groundwater can bind hydrophobic contaminants to form “complexes” and possibly affect their transport in the subsurface. The mobility of trace organic contaminants in soil originating from non-point source pollution may thus be affected by complexation reactions in the unsaturated zone. In order to predict the possible impact of such interactions on contaminant retention in soil, simulations have been made with a three-site sorption model. Two kinetic rate equations and an equilibrium Freundlich equation are used to describe possible sorption of two species of the contaminant (free or bound with dissolved organic matter) in a soil-water system. The equations governing the contaminant adsorption and the transport are simultaneously solved using an explicit-implicit finite difference technique, under steady-state water flow conditions. An analysis of the model's sensitivity to variations in the “complex” sorption rate constants and the complexation constant, Kc, demonstrated the relative importance of these processes and their effects on the vertical movement of the contaminant in soil. The influence of slow sorption kinetics for the “complex” varies as a function of residence time in the soil column, i.e. the pore-water velocity. Sorption of the “complex”, when it does occur, diminishes the “carrier-effect” of the complexation. If the “complex” is non-adsorbable on soil, the transport of contaminants with Kc values greater than 105 (mol/L)−1 will be significantly affected by dissolved organic matter concentrations typically encountered in soil-water systems. The possible application of the model to chemical transport studies in soil is discussed with respect to our present knowledge of complexation processes that can occur in field situations.
The Effect of Exchangeable Cations on the Permeability of a Bentonite to Be Used in a Stabilization Pond Liner
Authors: Büchler P. M.
Published: May 2018

The organophilic nature of bentonites exchanged with quaternary ammonium cations is used in sanitary engineering for the adsorption of organic pollutants. This paper deals with five different quaternary ammonium cations: tetramethylammonium, trimethylstearylammonium (C18), dimethylbenzyllaurylammonium (C12), trimethylpalmitylammonium (C16) and dimethyldistearylammonium. A Brazilian bentonite was treated with the above cations and the adsorption of vinasse organics was measured through the total organic carbon present in solution. The results show that tetramethylammonium cation is the most effective of those tested to make sodium bentonite more organophilic and the behaviour follows a Freundlich isotherm. If the isotherms are plotted in milliequivalents of the cation over the weight of the sodium bentonite the present experiments did not show an appreciable difference in the quantity adsorbed. Therefore, if cost is a determining factor, low molecular weight cations should be chosen. The modified bentonites were characterized by the X-ray diffraction patterns. For high molecular weight cations the interlamelar spacing is close to 18 Å but for tetramethylammonium it is 13.5 Å. In any case the replacement of sodium by a quaternary ammonium cation increases the capacity of the clay to adsorb organic molecules.
Treatability of High Strength Brewery Wastewater with Stabilized Refuse
Authors: Fan Kuo-Shuh
Published: May 2018

A column with a surface area of 790 cm2 and effective height of 105 cm was used for the study. The column was filled with stabilized refuse (which had been studied for two consecutive years regarding leachate recycling) compacted to an average density of 500 kg/m3. High strength brewery wastewater, with a COD of 6000 mg/l, was homogeneously trickled over the top of the refuse at daily flow rates of 8, 16, 24, and 36 liters/day. Each flow rate was maintained for more than three weeks to achieve steady performance. After six months of intensive study, it was demonstrated that the stabilized refuse had a very good ability to treat the brewery wastewater. The COD was reduced to as low as 60 mg/l, which was equivalent to a removal efficiency of 99%, after the wastewater had trickled through the 90 cm refuse layer. The COD reduction achieved in the stabilized refuse layer perfectly fitted the following equation:

The variations of major parameters such as pH, alkalinity, and volatile fatty acids, strongly indicated that acidogenesis occurred quickly in the first 15 cm. As the flow rate increased, acidogenesis occurred deeper in the column and its recovery became slower. The oxidation reduction potential (ORP) dropped to as low as −290 mV in the refuse column, indicating the anaerobic conditions of the system.
Waste Water Management in a Sugar Beet Factory: A Case Study of Comparison between Anaerobic Technologies
Authors: Iza J. , Palencia J. I. , Fdz-Polanco F.
Published: May 2018

The ACOR-l sugarbeet factory owns a waste water treatment plant which handles 2500 m3/d of medium strength wastewater (COD = 4000 mg/L). The system was designed to treat the excess wastewater from the beet transport circuit, some process streams, the sanitary waters and wastewaters from an alcohol distillery. The plant is based on two lagoons for equalization and pre-acidification of the waste, an Upflow Anaerobic Sludge Bed (UASB) reactor (efficiency > 97% soluble COD) and a small lagoon used for final polishing of the effluent.

A pilot-scale Fluidized Bed (FB) reactor was run in parallel with the UASB reactor to assess the capability of the FB system. There were two runs in consecutive campaigns, where results showed very good efficiency in spite of very high loading rates and low hydraulic residence times achieved in the FB system.
Management of Sugarcane Mill Wastewater in Hawaii
Authors: Chang L. J. , Yang P. Y. , Whalen S. A.
Published: May 2018

Current sugarcane mill wastewater management system in Hawaii was surveyed at Oahu Sugar Co. on the island of Oahu. Problems generated from the improper wastewater management such as odor nuisance, field silting, crop reduction and large land requirement, motivate a new management system for Hawaiian sugar industry. Based on the results of preliminary laboratory treatment on sugarcane wastewater, and the cost analysis for different alternatives, an appropriate wastewater management system for Hawaiian sugar industry is recommended. This system incorporates sedimentation, anaerobic pretreatment(UASB), and aerobic polishing(EAFB) for anaerobically treated effluent. It efficiently(≥99%) removes the organics and solids in wastewater within 2 days of hydraulic retention time provided. Therefore, the problems generated from the present treatment facility can be eliminated by implementing the proposed management system. More importantly, reuse of the properly treated wastewater for drip irrigation and cane washing will provide extra profit for the Hawaiian sugar industry.
Treatment of Monosodium Glutamate Fermentation Wastewater with Anaerobic Biological Fluidized Bed Process
Authors: Tseng Szu-Kung , Lin Min-Ray
Published: May 2018

This study is to explore the feasibility of the treatment of the MSG Fermentation wastewater by AFBBR (Anaerobic Biologial Fluidized Bed Reactor) Method, and intends to solve the serious pollution problem of MSG industry by the advantages of AFBBR Method. The results show that the wastewater BOD removal efficiency is very high due to this treatment. When the organic loading is below 14.0 kg-BOD/m3.day, the BOD removal efficiency can reach 90% or more. Since the wastewater contains the undissolvable difficult biodegradation organic matter, the COD removal efficiency only reaches 65% maximum. The methane content in biogas can achieve 80.8%. When the digestion temperature is 35°C, biogas production per kg is maximum 367.8 1. The treatment results indicate if the organic loading is in the range of 10.1-31.1 kg-COD/m3.d, and the operation condition is appropriate, we will get a very good digestion efficiency, i.e. the feasibility of this method for MSG Fermentation Wastewater Treatment is very high.
Starting-Up of a Full-Scale Two-Phase Contact Process Treating Citric Acid Wastewater
Authors: Gönenç I. E. , Kerestecioǧlu M.
Published: May 2018

The results of three years' starting-up period of the phased-recycled flocs system (contact process) treating citric acid factory wastewater are presented in the light of the process characterization approach. After the description of the system and starting-up studies, the reasons of and remedies for the problems of starting-up are discussed with emphasis laid on the biochemistry and microbiology, design and operation parameters,and environmental factors of the anaerobic process.
Comparative Evaluation of Treatment Alternatives for Wastewaters from an Edible Oil Refining Industry
Authors: Eroglu V. , Ozturk I. , San H. A. , Demir I.
Published: May 2018

The aim of this study was to investigate the treatment alternatives for high-strength acid waters from an edible oil refinery and to determine an appropriate treatment system. The study was conducted in three stages: waste characterization, treatability studies and wastewater treatment system design. Based on preliminary lab-scale flotation experiments a full-scale Dissolved Air Flotation (DAF) plant was constructed. The removal of fatty materials (FM) was more than 80% without using any chemical reagent in the DAF unit. Physico-chemical treatability studies were conducted by using FeCl3, A12(SO4)3 and Ca(OH)2 as coagulants. Aerobic treatability experiments were carried out by means of an insitu pilot-scale activated sludge (AS) unit with a volume of 240 1. A BOD5 removal of 85% and FM removal of 95% were achieved for the organic loading rate (OLR) of 0.45 kg BOD5kg VSS.d. The biological sludge had an excellent settling property with a sludge volume index (SVI) of 55 to 74 ml/g. Anaerobic sulphate removal kinetics was also investigated as a comparable alternative to physico-chemical treatment both in a pilot upflow anaerobic sludge blanket reactor (UASBR) and anaerobic filter (AF). Anaerobic treatability experiments showed that the linearized second-order substrate removal kinetics could be used to explain the anaerobic sulphate removal from acid waters of edible oil refineries. The maximum sulphate removal efficiency of the AF was about 60% for a hydraulic retention time of two days.
Managing Change in an Environmentally Conscious Society: A Case Study, Gothenburg (Sweden)
Authors: Balmer P. , Frost R. C.
Published: May 2018

The treatment and disposal of sewage sludge in environmentally conscious societies is becoming increasingly problematical due, in large part, to public attitudes. Strategies have to be developed which either successfully defend existing routes or which manage changes that have public support. A case study of managing change at a large wastewater treatment plant, serving Gothenburg, Sweden, is presented. Three radically different alternatives to the current practice, of lime addition to dewatered raw sludge and disposal to land reclamation, were appraised to a common set of criteria and compared with the existing route. The options considered were incineration, drying of dewatered anaerobically digested sludge, and disposal of dewatered anaerobically digested sludge to underground cavities. An account is given of the public discussion meetings that were held at strategically important times, the views expressed at these being taken into account by GRYAAB's management board in their decision to opt for the disposal of sludge to underground cavities.
Heavy Metals and Heat Value in Sewage Sludge
Authors: Reimann Dieter O.
Published: May 2018

Of the 50 × 106 Mg of sewage sludge (5% dry solids) produced per year in the FRG, 60% is dumped, 30% used in agriculture or composted, and 10% is combusted.

For all the different types of sludge utilization, thermal sludge treatment and disposal or dumping, major problems are created by pollutants in the sludge.There may be serious levels not only of salts and organic pollutants, but also especially of heavy metals.The content of these pollutants causes environmental dangers in soil, plants, groundwater and in the air.

For the thermal treatment or disposal of sludge, knowledge of the salt and heavy metal content is important for the choice of the right flue gas cleaning system.Only by this means can hazardous emissions into the air be avoided.

The advantage of thermal sludge treatment as opposed to the dumping and utilization systems must be seen in the thermal destruction of the organic pollutants.At the same time, as a large part of the heavy metals are evaporated by the high burning temperature, they are taken up into the flue gas and can be captured by condensation on the filter-ash or in the scrubber water.

In the combustion of sludge its heat value is very important, and is dependent on the organic matter and the water content of the sludge, which can be influenced by dewatering systems. Comparative results on heavy metals and heat values for different sorts of sludges have been collected in a great number of investigations.The results of these investigations are presented and should serve as a basis for the prevention of negative environmental influences by the utilization, dumping or burning of sludge.
The Effect of Shear on Conditioning: Chemical Requirements during Mechanical Sludge Dewatering
Authors: Novak John T. , Lynch Daniel P.
Published: May 2018

In this study it is shown that the shear occurring in a sludge cake during dewatering can create an increase in polymer demand. Comparisons between a laboratory mixing unit and a pilot filter press indicate that polymer requirements for mechanical dewatering equipment can be predicted using laboratory procedures.
Potential Utilization of Sewage Sludge
Authors: Aziz M. A. , Koe Lawrence C. C.
Published: May 2018

Singapore, a tropical-island city-state, is served by six modern sewage treatment plants with a combined design capacity of around 900,000 m3/day. Currently, 96.5 percent population of Singapore is served by sewer systems. Total production of raw sludge and digested dewatered sludge from six sewage treatment works in 1988 was about 2,546,000 m3 and 39,000 m3 respectively. Mast of the dewatered sewage sludge is used as a soil conditioner and landfilling. Since land is limited in Singapore, alternative means of disposal of dewatered sewage sludge are essential. Therefore, studies were conducted to investigate the feasibility of using dewatered sewage sludge for producing building materials and products like aggregates, bricks, paving blocks, tiles, drain sections and pipes. Studies were also conducted to use sewage sludge as a conditioning additive to improve the characteristics of poor subgrade soils for road construction. Attempts were also made to utilize sewage sludge as a filler material in concrete and bituminous mixes. Findings of these investigations have shown encouraging results. This paper presents the results of these studies on potential application of sewage sludge for beneficial uses.
Improved Centrifuge Sludge Dewatering by Automatic Backdrive Torque Control
Authors: Garelli B. A. , Kokat E. L. , Schwartz B. J.
Published: May 2018

An investigation of different automatic torque control systems for performance optimization of solid bowl centrifuges was conducted at the Stickney Water Reclamation Plant of the Metropolitan Water Reclamation District of Greater Chicago (District). Two automatic hydraulic backdrives and a direct current automatic torque controlled backdrive were tested on centrifuges used for dewatering digested sludge conditioned with a polymer and a combination of polymer and ferric chloride. The centrifuge unit of an advanced design coupled with the direct current automatic torque controlled backdrive produced a cake having a solids content of 30% and a solids capture of 97%. The regular production unit produced a cake having a solids content of 15% and a solids capture of 85%.
Enhancing Nitrogen Removal in Activated Sludge with Fixed Biomass
Authors: Bonhomme M. , Rogalla F. , Boisseau G. , Sibony J.
Published: May 2018

To upgrade existing activated sludge treatment plants, different techniques that would remove an important flux of nitrogen rapidly on a great number of units were investigated. Nitrification with conventional activated sludge systems requires considerable multiplication of tankage volume. The necessary investment and space is not always available, especially since many older plants are now in urbanized areas. To lower the nitrogen load in receiving water, the first priority should be to obtain partial nitrogen removal with existing plants, using methods that are simple to adapt.Three techniques were tested on large scale: submerged elements in aeration basin to add fixed biomass, contact stabilisation that allows a higher sludge age in the same tankage volume, and adding submerged biotower packings as a tertiary aeration stage.

In a full scale unit (4000 m3/d), one complete section of the plant fitted with biofilter packing was operated in parallel with a similar unmodified section as reference. The volume occupied by the fixed beds was varied between 20 and 40 % of the tank. The submerged elements improved removal efficiency, to maintain effluent quality at higher loadings or obtain lower residual pollution values in existing plants. The biofilm evolution and the hydraulic behaviour of the packing was followed. No significant change in sludge settleability was observed, but fixed biomass addition reduced sludge production because of a lower overall mass loading. The resulting higher sludge age allowed the ammonia oxidizers to remain in the mixed population beyond usual F/M limits, but no installation of nitrifiers on the support media could be observed.

To verify the limits of immersed plastic surfaces for nitrification, an aerated column was fed with effluent of a highly loaded activated sludge plant. In opposition to carriers submerged in mixed liquor, nitrifier attachment was obtained, and COD and SS removal for effluent polishing was achieved. With a carbon loading exceeding 1,5 kg COD/m3 d, a maximum oxidation rate of 0,4 kg N-NH4/m3 d could be obtained.

A pilot unit was tested to assess the potential volume reduction for nitrogen elimination by contact stabilisation. This configuration stores the highly concentrated return sludge in a reaeration basin, and keeping only the minimum detention time in the contact basin to obtain nitrification. Also, an increased carbon load in the contact basin enhances denitrification. For urban wastewaters with a COD/N ratio of about 10, complete oxidation and partial removal of nitrogen were obtained with a volume loading of 1,5 kg COD/m3 d. Nitrogen removal rates of 0,15 kg N/m3 d were measured both in the anoxic and the aerobic part of the contact basin. The contact stabilisation mode was then tested on full scale combined with submerged biomass carriers. A consistant nitrogen elimination of 50 % was obtained with aeration detention times of about 4 hours.
The Submerged Biofilm Process as a Pre-Treatment for Polluted Raw Water for Tap Water Supply
Authors: Takasaki M. , Kim H. , Sato A. , Okada M. , Sudo R.
Published: May 2018

The submerged biofilm process is a promising system for polluted raw water pre-treatment systems. General treatment performance and factors affecting treatment efficiency were investigated through pilot plant scale experiments using water from four different lakes. Regarding the quality of the raw waters, BOD was generally below 10 mg/l and the ammonium nitrogen (NH4-N) concentration was below 0.4 mg/l. The efficiency of removal of NH4-N was about 80% under complete mixing conditions and when the raw water quality did not fluctuate rapidly. Under the adverse conditions of the low water temperatures which occurred in winter and spring, the removal of NH4-N was 60 to 80%. The critical NH4-N concentration was observed to be approximately 0.01 to 0.02 mg/l, and a moderate decrease in E260 was also observed in the experiments. Overall treatment performance of the submerged biofilm process was superior in those systems with carriers which were not likely to become clogged.
Concepts and Models for Biofilm Reactor Performance
Authors: Arvin E. , Harremoës P.
Published: May 2018

This paper reviews the state of knowledge of the basic mechanisms governing transformation of pollutants and the present approaches with which to predict the performance of biofilm reactors. The design of biofilm reactors is based mainly on empirical loading criteria or empirical design formulae. Introduction of more stringent effluent requirements, new types of biofilm reactors, as well as application of biofilm reactors to more untraditional types of waste materials, calls for new design procedures with higher degrees of confidence. Most new attempts to model biofilm reactors are based on fundamental principles for mass transport to and through biofilms coupled with kinetic expressions for pollutant transformations in the biofilms. A simple simulation model based on half order kinetics is able to describe the removal of soluble substrates, mineralisation of organic matter, nitrification and denitrification. A simple first order kinetics is able to predict degradation of some xenobiotics. Advanced simulation models appearing in the past few years show a strong promise for detailed analysis of the effect of variation in influent waste characteristics, population dynamics, reactor configuration, etc. However, none of the models are able to predict properly the removal of particulate matter and mixtures of several groups of industrial organic chemicals. Again, insight in the basic removal mechanisms is required.
Biological Fluidized Bed Reactor: Hydrodynamics, Biomass Distribution and Performance
Authors: Hermanowicz S. W. , Cheng Y.-W.
Published: May 2018

Performance of a pilot-scale denitrifying biological fluidized bed was analyzed with special consideration to the effects of mean cell residence time (MCRT) and biomass distribution in the reactor. An optimum MCRT exists at which volumetric removal rate is maximized. The decline of substrate removal rate at short MCRT is caused by small amount of biomass in the reactor. At long MCRT the decline of substrate removal rate was attributed to decreasing biofilm effectiveness and smaller solids holdup.
Denitrification by Fluidized Biofilm Reactor
Authors: MacDonald David V.
Published: May 2018

The Rancho California Wastewater Reclamation Plant, which has a design capacity of 23.6 Ml/d, is located in Southern California approximately 64 km northeast of the City of San Diego. The effluent from this plant is used for irrigation and groundwater recharge. In order to protect the local groundwater from nitrate contamination, the plant must nitrify and subsequently denitrify to a nitrate-nitrogen concentration of 2.5 mg/l. The influent nitrate-nitrogen concentration, to the denitrification facility, is normally in the range of 15 to 20 mg/l. Denitrification is achieved by three upflow, fluidized bed biofilm reactors.

The reactor is designed for a loading of 3.0 kg of N03−N per day per m3 of expanded bed volume. The upflow velocity is 0.4 cm/s and the reactor has an empty bed contact time of 10 minutes at design flow. Each reactor has a design capacity of 7.5 Ml/d. The biofilm is grown on a media of sand with an effective size of 0.6mm and a uniformity coefficient of 1.2. The reactor has a concrete perforated underdrain, 0.6 meters of support gravel and 1.2 meters of sand. Following a two month start-up period, the facility has consistently removed 95 to 100 percent of the nitrate nitrogen. The objective of this paper is to present the design criteria and evaluate one year of operating performance.
Small Wastewater Treatment Plants in Switzerland
Authors: Boller Markus , Deplazes Gieri
Published: May 2018

In Switzerland, the installation of small treatment plants in rural areas is being and will be intensified. In order to remove the numerous small pollution sites, new guidelines have been established in which basic information is given on the procedure of how to consider local circumstances of wastewater characteristics and of how to integrate local quality requirements of the receiving water into the design of small plants. The statistics on small treatment plants show a preferential application for extended aeration, RBCs and trickling filters. Due to the lack of skilled operation and maintenance, the performance of small treatment plants is not always satisfactory. New economic, reliable and less service-demanding methods are increasingly studied and applied.
Small Sewage Treatment Plants and Wastewater Reuse in Cyprus
Authors: Hadjivassilis I.
Published: May 2018

The rapid touristic development in the coastal areas of Cyprus resulting in higher water consumption, the protection of environment and water resources and the needs of reuse of wastewater, contributed to the improvement of local technology for sewage treatment and wastewater reuse for irrigation. In the last ten years, due to the lack of central sewerage systems, approx. two hundred small wastewater treatment plants have been installed, mainly in coastal areas of the island.

The method applied for the biological treatment is the activated sludge extended aeration process. The tertiary treatment based on high-speed depth filtration consists of two vertical pressure multilayer filters, working in series. Additionally, chemicals are injected for disinfection, coagulation/flocculation allowing the production of high quality of water.

Plants regularly maintained are operating with very good results, so that the treated water has the following characteristics:BOD5: < 5mg/lS.S.: < 5 mg/lTurbidity: < 3 NTUResidual chlorine: 1.0-1.5 mg/l

The water can be used for unrestricted irrigation. It has been proved that the installation of small sewage treatment plants and the wastewater reuse for irrigation in Cyprus is a profitable investment, preventing at the same time the pollution of the environment.
Small Wastewater Treatment Plants in Norway
Authors: Ødegaard H. , Storhaug R.
Published: May 2018

About 70 % of the total number of advanced (biological, chemical or biological/chemical) wastewater treatment plants in Norway are small (100 - 2000 PE). More than half of the small plants (55 %) are based on biological/chemical treatment. Simultaneous precipitation and post precipitation based on the activated sludge process is dominating even if systems based on biofilm processes are gaining more and more popularity.

The State Pollution Control Authority has made recommendations on design of small wastewater treatment plants. Two systems are recommended; one based on a low loaded activated sludge process with querning of particulate matter as pretreatment and with a separate waste sludge holding tank, and one based on a low loaded biofilm system (biofilter, RBC, etc.) with a large septic tank serving both as pretreatment and waste sludge holding tank.
Soil Absorption Systems and Nitrogen Removal
Authors: Cochet C. , Derangère D. , Rousselle T.
Published: May 2018

The mass of nitrogen wasted from conventional soil absorption systems used as waste water drainage and treatment facilities sometimes contributes to pollution of vulnerable groundwater tables. The scope of nitrogen compounds transformation along the different stages of treatment shows that nitrate is quite often the nitrogen end product of efficient aerobic soil treatment for septic tank effluent. Results are reported from long term on-site compact sand filter study, showing that nitrate production depends on hydraulic conditions, but can be very efficient when filtering media is kept unsaturated, for an experimental hydraulic load of 15cm/day When clogging of the system is induced by increasing hydraulic load, nitrate production decreases drastically while removal for other parameters such as organic matter is also affected. A synthetic effluent study gives results on nitrification and denitrification operating conditions applied to sand columns and shows that denitrification can be efficient as a second step of treatment when an extra carbon source is added at the head of a second anaerobic sand column.
Intermittent Aeration for Nitrogen Removal in Small Oxidation Ditches
Authors: Araki Hiroyuki , Koga Kenichi , Inomae Katsuto , Kusuda Tetsuya , Awaya Youichi
Published: May 2018

An intermittent aeration method is available for nitrogen removal in a small oxidation ditch. The purpose of this study is to establish a basis for design and operation of the oxidation ditch with the intermittent aeration method. Discussions on the essential process parameters depending on cycle time tc, aerobic period ta, specific nitrification rate vn and specific denitrification rate vd were carried out by using a continuous-flow stirred-tank model. It is shown theoretically that an optimum range of the aerobic time ratio (ta/tc) for nitrogen removal exists in the region of 1/v n* to 1-1/vd*. From evaluating an amount of leaking nitrogen in the intermittent aeration, the cycle time is proved to be minimized. Experiments in a full scale test plant were conducted to affirm the validity of the proposed basis. It is confirmed that the total nitrogen removal efficiency of 90% is achieved and the estimated removal efficiencies by this basis agree well with the experimental data. The newly proposed basis and parameters for nitrogen removal using the intermittent aeration method are available for not only an oxidation ditch but also other nitrogen removal processes by single sludge systems.
Biofiltration as a Compact Technique for Small Waste Water Treatment Plants
Authors: Desbos Gilbert , Rogalla Frank , Sibony Jacques , Bourbigot Marie-Marguerite
Published: May 2018

Biological aerated filters combine bacterial degradation of pollution by fixed biomass with physical filtration in a single reactor. Removal rates become independent of clarification and sludge setueability limits, and concentration of biomass is increased. Nitrifiers attach to the media, allowing nitrogen removal without sludge age constraints.

Several fullsize plants with the BIOCARBONE process for industrial and municipal wastewater treatment have established the compacity, ease of operation and high removal rates achievable with this advanced treatment system. A new biofilter design offering simplified operation and increased performance is presented, which allows implementation of biofiltration for small wastewater treatment plants.

Design data for carbon and nutrient removal were collected during extensive pilot tests. Hydraulic conditions and pollution loadings were varied in order to optimize the biological and operational parameters of the filter. The combination of an anaerobic and an aerobic zone eliminates the need for primary sedimentation.

Pollution removal rates up to 20 kg COD/m3 d could be achieved, and a widely fluctuating load of up to twice that average loading can be treated without major effluent deterioration. If lower carbon loadings are used, nitrification is achieved in the upper aerated zone. By recirculating the effluent into the non-aerated lower zone, carbon and ammonia oxidation as well as denitrification and suspended solids retention could be achieved with an overall hydraulic retention time of four hours in one reactor.
Primary Chemical Treatment Minimizing Dependence on Bioprocess in Small Treatment Plants
Authors: Galil N. , Rebhun M.
Published: May 2018

In wastewater from small communities, institutions, hotels, camps and tourist areas the major pollutants such as organic matter, oil and grease and organic nitrogen are mainly in particulate form, while the soluble fractions of organics and nitrogen are low. This is due to the short residence times in the sewerage systems preventing decomposition and lysis. Such wastewaters are also characterized by high variations in pollution load, mostly in the particulate fraction. Small plants, treating wastewater for discharge to lakes or rivers, have to remove organic pollutants and nutrients, mainly phosphorus. Chemical flocculation-sedimentation, as primary treatment, was considered a promising process combination to obtain reliable operation and for minimizing effects of variations in flow and load. Two possible process combinations were studied: a. chemical flocculation-sedimentation as primary stage, followed by biotreatment (CBT); b. biotreatment of raw wastewater, followed by chemical flocculation-sedimentation (BCT). It was found that primary chemical treatment by alum, or lime, removes more than 90 percent of the suspended solids, colloids, phosphates, oil and grease; the organic matter as BOD and organic nitrogen removals were about 70 percent. By removing the particulate organic matter and other disturbing factors the successive bioprocess in CBT was substantially improved: the growth rate constants for general biomass and for nitrifiers as well as the removal rates were higher for CBT than for BCT; the critical sludge age for nitrification in CBT was 4 days, as compared to 10 days in BCT. The reduction of organic load by about 70 percent, producing a more uniform influent and the better bio-kinetics achieved in CBT, enable a considerable economy in the bioreactor volume and lower energy requirement. Experimental results showed that the CBT sequence enables lower sludge production containing higher concentrations of solids, most of them inorganic.
Zero Discharge through Innovative Application of Intensive Silviculture to Effluent Disposal from a Small Canadian Wastewater Treatment Plant
Authors: Laughton P. J. , Papadopol C. S. , Jaciw P.
Published: May 2018

The design and practical experience gained from the operation of a small activated sludge wastewater treatment facility, incorporating zero effluent discharge through evapotranspiration utilizing a multi-clonal poplar forest, is described. Secondary treated effluent was seasonally applied to a forested plantation through an automated sprinkler system with the rate being calculated daily based on information from an automatic weather station and using a modified Penman approach. For the past six years, significant growth rhythm differences were found amongst the poplar clones. The influence of effluent irrigation on growth, with its additional nutrient content, is positive but not as yet deemed significant. Work to date would suggest that evapotranspiration of effluent by the plantation can be 3-4 times greater as compared to grass. This is attributed to increased foliage, larger direct evaporation and advection. Since the structure of plantation can be manipulated to a certain extent, it is speculated that further increases of evapotranspiration can be obtained even in a sub-humid climate. The concept could be applied in various geographic areas with existing technology and software allowing for the complete automation of an effluent recycling system.
Sludge Removal from Some Wastewater Stabilization Ponds
Authors: Carré J. , Laigre M. P. , Legeas M.
Published: May 2018

The study of sludge accumulation in the first ponds of 12 treatment plants under oceanic climate showed a mean rate of accumulation of 2.8 cm per year corresponding to 0.12 m3 of sludge per inhabitant per year.

Desludging was required about operation periods of 6 or 7 years. Sludge removal by pumping after or without emptying water is the most convenient and with a mean cost of 40FF per m3 the cheapest method. Mean desludging cost is eight times lower than mean investment cost. With regard to their agronomic characteristics stabilization pond sludges have a low fertilizer value because of their long maturation time.
The Experience and the Results of Operating Small Wastewater Treatment Plants
Authors: Rismal Mitja
Published: May 2018

About 15 years of experience gained from operating 7 small waste water treatment plants between 150-500 p.e. and 6 plants of 2000-3000 p.e. capacity are described. All of the plants involved are low-loaded activated sludge plants with water jet aeration generated by screw or propeller pumps which both proved to be efficient in aeration while secure and simple in operation. In comparison with other types of small treatment plants in our country (rotating discs and bubble aeration activated sludge plants), they proved to be reliable and simple in operation and produce an effluent of good quality. The energy consumption and the necessary flow velocites in aeration tanks are computed and measured.
Bottlenecks in the Implementation of On-Site Wastewater Treatment Plants on a Large Scale in The Netherlands
Authors: Fastenau Frits A. , van der Graaf Jaap H. J. M. , Martijnse Gerard
Published: May 2018

More than 95 % of the total housing stock in the Netherlands is connected to central sewerage systems and in most cases the wastewater is treated biologically. As connection to central sewerage systems has reached its economic limits, interest in on-site treatment of the domestic wastewater of the remaining premises is increasing. A large scale research programme into on-site wastewater treatment up to population equivalents of 200 persons has therefore been initiated by the Dutch Ministry of Housing, Physical Planning and Environment. Intensive field-research work did establish that the technological features of most on-site biological treatment systems were satisfactory. A large scale implementation of these systems is however obstructed in different extents by problems of an organisational, financial and/or juridical nature and management difficulties.

At present research is carried out to identify these bottlenecks and to analyse possible solutions. Some preliminary results are given which involve the following ‘bottlenecks':-legislation: absence of co-ordination and absence of a definition of ‘surface water';-absence of subsidies;-ownership: divisions in task-setting of Municipalities and Waterboards; divisions involved with cost-sharing;-inspection; operational control and maintenance; organisation of management;-discharge permits;-pollution levy;-sludge disposal.

Final decisions and practical elaboration of policies towards on-site treatment will have to be formulated in a broad discussion with all the authorities and interest groups involved.
Leachate Treatment: Design Recommendations for Small but Extremely Fluctuating, Highly Polluted Quantities of Water
Authors: Heinz Hartmann Karl , Hoffmann Erhard
Published: May 2018

Today's practice in leachate treatment and disposal in the FRG comprises two possibilities:a) the combined leachate domestic wastewater treatment (transportation to the treatment plant either using the sewer system or tank trucks)b) complete, decentralized treatment at the source of the leachate production.

As a result of the updating of the general water management law (WHG § 7a) the discharge of waste waters containing dangerous substances (e.g. AOX) into sewer systems is no longer permitted. As there is no possibility of a selective removal of the hazardous substances, the future consequence will be that the whole amount of leachate has to be treated at the landfill site.

Existing leachate treatment plants are often designed for average loading rates. Because of the high fluctuations of the leachate quantity such plants are often overloaded. In the past there were two solutions:a) temporary transportation to a municipal treatment plant using trucks,b) recycling of the excessive leachate volume.

As transportation is no longer accepted there is only the possibility of recycling left. The feasibility of buffering the runoff peaks has not yet been studied in detail (reservoir management). This cost-favourable option (earth basin with sealing) offers two advantages. First, the plant design can be based on mean conditions while secondly the loading of the plant will be almost constant (no variation concerning the hydraulic loading; concentration equalization effect of the storage tank).

Herewith an attractive way of adapting existing plants to the time dependent changing requirements is available.
Packed-Entrapped-Mixed Microbial Cells for Small Wastewater Treatment
Authors: Yang P. Y. , Wang M. L.
Published: May 2018

The primary goal of the research is to develop and evaluate a biological treatment system in which mixed microbial populations are physically immobilized by entrapment. The immobilized system was evaluated initially for its ability to remove simple benzene-based compounds from a synthetic wastewater as a model for treating pesticide-containing waters.

Cellulose triacetate was used as the preparation of monocarrier and combined cellulose triacetate and calcium alginate were used for the preparation of bi-carrier. Phenol was used as substrate to test the entrapped mixed microbial cell process. Process performance including steady state, shock load and comparison of entrapped microbial cell process with and without entrapped microbial cell was investigated. It was concluded that the critical loading rate for phenol synthetic wastewater appeared to be 9 g COD/L/day. The COD removal efficiency could be maintained higher than 90%. Because of the low effluent suspended solid concentration, conventional-secondary-settling tanks could be eliminated. Also, the process could take both concentration and hydraulic shock loads of phenol synthetic wastewater successfully without the need of external sludge recycling. The equalization and external sludge recycling facilities equipped in the conventional wastewater treatment plant could be eliminated. When the process is operated only at low COD loading rate (less than 1.3 g/L/day), entrapped cells might not be required. However, when operated at higher loading rate, combined adsorbed and entrapped cells appeared to remove phenol more efficiently. For the application, mono-carrier (cellulose triacetate) is preferable to bi-carrier (cellulose triacetate and calcium alginate), since it is easier to prepare and the operational performance is better. Therefore, the application of packed-entrapped mixed microbial cell process for treatment of small-toxic-organic wastewater holds great potential.
Upgrading of the Treatment Plants in Stockholm to Meet More Stringent Requirements
Authors: Hultgren J. , Reinius L.-G. , Tendaj M.
Published: May 2018

The purification requirements for the Stockholm sewage treatment plants will become more stringent in the future. The expected limit values for the effluent, expressed as annual mean values, are for BOD7, Tot-P, and Tot-N, 10, 0.3 and 15 mg/l respectively.

If these contents are multiplied by the design flow values for the three plants, we obtain the maximum quantities which may be released. If the relevant authorities permit the municipality to distribute these total quantities as desired between the three plants, future necessary extensions can be optimized. The following main principles apply to an extension of the three plants:

Loudden sewage treatment plant: This comparatively small treatment plant could, if the requirements are lower than in the other two plants, continue in operation with no other extensions than the inclusion of anoxic zones. It would, however, be necessary to refurbish the plant after a number of years of neglected maintenance.

Bromma sewage treatment plant: The biological stage was extended during the 1982-84 period. For this reason, the municipality suggests that no further extensions of the aeration tanks be required, before 1995 at the earliest. A nitrogen removal with outgoing contents of Tot-N of 15-17 mg/l is expected to be achieved by measures taken to reduce the load on the biological stage instead. These measures consist of centrifuging the excess sludge and pumping it directly to the digesters instead of returning it to the inlet. Furthermore, separate treatment of the reject water from the sludge centrifuges is planned. A third measure could be changing over to a more efficient precipitation chemical to permit a further reduction of the load on the biological stage with regard to, inter alia, BOD7, Tot-N etc. To meet the requirements for phosphorus removal (0.3 mg/l), the plant will be extended with a filter stage after the existing biological stage.

Henriksdal sewage treatment plant: At this plant, which is the largest of the three, the largest extensions are planned. To meet the requirements for nitrogen removal, the present volumes in the aeration tanks will be tripled and will be utilized as anoxic and aerated zones as required. Three new lines with aeration tanks and secondary sedimentation tanks will be constructed. The existing aeration tanks will also be deepened from 5 to 12 m.

The requirements for low phosphorus contents in the effluent will be met by installing a filter stage, as in the Bromma plant.