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The activated sludge (AS) process is widely applied in dyestuff wastewater treatment plants (WWTPs); however, the nitrogen removal efficiency is relatively low and the effluent does not meet the indirect discharge standards before being discharged into the industrial park's WWTP. Hence it is necessary to upgrade the WWTP with more advanced technologies. Moving bed biofilm processes with suspended carriers in an aerobic tank are promising methods due to enhanced nitrification and denitrification. Herein, a pilot-scale integrated free-floating biofilm and activated sludge (IFFAS) process was employed to investigate the feasibility of enhancing nitrogen removal efficiency at different hydraulic retention times (HRTs). The results showed that the effluent chemical oxygen demand (COD), ammonium nitrate (NH4+-N) and total nitrogen (TN) concentrations of the IFFAS process were significantly lower than those of the AS process, and could meet the indirect discharge standards. PCR-DGGE and FISH results indicated that more nitrifiers and denitrifiers co-existed in the IFFAS system, promoting simultaneous nitrification and denitrification. Based on the pilot results, the IFFAS process was used to upgrade the full-scale AS process, and the effluent COD, NH4+-N and TN of the IFFAS process were 91-291 mg/L, 10.6-28.7 mg/L and 18.9-48.6 mg/L, stably meeting the indirect discharge standards and demonstrating the advantages of IFFAS in dyestuff wastewater treatment. [ABSTRACT FROM AUTHOR]

Critical barriers to safe and secure drinking water may include sources (e.g. groundwater contamination), treatments (e.g. treatment plants not properly operating) and/or contamination within the distribution system (infrastructure not properly maintained). The performance assessment of these systems, based on monitoring, process parameter control and experimental tests, is a viable tool for the process optimization and water quality control. The aim of this study was to define a procedure for evaluating the performance of full-scale drinking water treatment plants (DWTPs) and for defining optimal solutions for plant upgrading in order to optimize operation. The protocol is composed of four main phases (routine and intensive monitoring programmes - Phases 1 and 2; experimental studies - Phase 3; plant upgrade and optimization - Phase 4). The protocol suggested in this study was tested in a full-scale DWTP placed in the North of Italy (Mortara, Pavia). The results outline some critical aspects of the plant operation and permit the identification of feasible solutions for the DWTP upgrading in order to optimize water treatment operation. [ABSTRACT FROM AUTHOR]

In the early nineties the region of Central and Eastern Europe (CEE, more than 1 million km² and 100 million inhabitants) went through fundamental political, economic and social changes which eventually led to the European integration process. This positively influenced urban water and wastewater management, which had an unbalanced structure and rather low level of development. The paper outlines first the 1990 situation (water supply, sewerage and wastewater treatment (WWT)) and the infrastructure development of the last two decades, on the basis of a comprehensive data collection for six countries (Bulgaria, the Czech Republic, Hungary, Poland, Romania and Slovakia). Austria serves as a reference basis. Alterations of some of the drivers such as GOP (Gross Domestic Product), water tariff, investment funding and legislation are studied in detail. Then, the paper focuses on WWT by analyzing data of 20 large plants. lnfluent and effluent quality is evaluated. Technology indicators are estimated and assessed. They include plant removal rates and violation ratios assuming the application of the Urban Wastewater Directive, primary clarifier removal rates, actual anoxic volume and sludge age in comparison with the recommendations of the AN guideline, criteria of secondary settling tanks and energy consumption. Finally, nutrient removal rates and upgrading options are outlined. [ABSTRACT FROM AUTHOR]

The STP Uithoorn will be upgraded to accommodate the treatment of wastewater from a growing population and to meet more stringent nutrient discharge limits in 2006. In 2003 a system choice and preliminary design was made for the upgrading. A special feature is the nutrient rich wastewater flow from the rapidly developing horticulture in the area. Since the future loads from horticulture are highly uncertain, flexibility of the STP after upgrading is an important issue. A three stage system was selected: improved physical-chemical primary treatment, secondary treatment by activated sludge, and tertiary treatment by denitrifying filters. In this way an important part of the existing infrastructure can be reused, and flexibility is assured by constructing the tertiary treatment in modules and by providing a wide range of operational control possibilities. In this paper the process of system choice and selection of type of tertiary treatment are described, as well as the optimisation of the existing treatment. In order to determine the feasibility of allowing a high loading rate on the existing secondary clarifiers, a two-dimensional hydraulic model of the clarification process was used. [ABSTRACT FROM AUTHOR]

The Mèze stabilisation pond system has been monitored over more than 20 years. Despite the enlargement of the plant, the organic load doubled between the early 1980s and recent years, the removal of organic matter and nutrients has been maintained at the same level for COD and increased for BOD5, N and P. Combining anaerobic, step-fed aerated and maturation ponds and multiplying the number of cells resulted in a significant improvement in the performances of the plant. Respectively 34, 24 and 23% of the applied COD was eliminated in the anaerobic, the step-fed and the first three maturation ponds, while the figures for BOD5 were 47, 26, and 19% respectively. 38% of the applied nitrogen was eliminated in the first three maturation ponds. Nitrification and denitrification seem to be a major process of nitrogen removal in warm periods. Most of the phosphorus removal was observed to take place in the two polishing ponds. [ABSTRACT FROM AUTHOR]

Ammonium selective natural zeolite clinoptilolite is suggested as a possible support material for nitrifying biofilms to help improve effluent ammonium quality through its high capacity of ammonium removal in the process of ion exchange. This will especially be helpful in cases where the biofilter receives peak or variable loads routinely or occasionally. At the time of peak loads or shocks of ammonium, ion exchange capacity will provide a buffer for the effluent ammonium quality. Data to support this suggestion is presented. [ABSTRACT FROM AUTHOR]

Käppala Association has the responsibility to receive and treat wastewater from 11 municipalities situated just north of Stockholm in Sweden. Running a tunnel system, 60 km long, and a treatment plant meets this responsibility. The plant is situated in Lidingö, northeast of Stockholm. The load 2002 corresponds to about 520,000 p.e. During the 1990s the plant was upgraded and expanded to meet an increasing population and more stringent discharge limits. Nitrogen removal was introduced. The expansion was done in two steps; the first step comprised a new plant beside the old one both situated in rock. This part, which included the filtration step, was taken into operation in 1998. Then the old plant was upgraded to the same technical standard as the new part. His Majesty the King of Sweden inaugurated the whole new and upgraded plant in April 2000. A total of 1.3 billion Swedish crowns were invested corresponding to about 140 million euro. The plant's performance is good. There is no trouble keeping the discharge limits, 10 mg/l for BOD7 and total nitrogen and 0.3 mg/l for phosphorus. However the bio-P process has not been altogether successful. We haven't been able to fulfill our goal to reduce the use of iron sulphate. We will during 2003 go on in our investigations concerning running the plant with a combination of bio-P and chemical precipitation. [ABSTRACT FROM AUTHOR]

For the upgrade and expansion of an existing caprolactam wastewater treatment plant, a freely floating sponge media (BioCube) process was selected based on extensive pilot-plant tests, due to extreme space constraints. In order to protect nitrifier inhibition caused by high strength organics in caprolactam wastewater, the pilot plant consisted of an organics removal reactor, which functioned as a pretreatment for nitrification, and followed the nitrogen removal reactor. The suspended MLSS was 1,800-4,000 and the media attached MLSS was maintained at 22,000-26,000 mg/L. The final effluent COD was noticeably low, around 20.4-37 mg/L, even with fairly large fluctuations in the feed levels, between 1,400-6,770 mg/L. The removal of total nitrogen with the system, when denitrification was close to completion, was approximately 97.6%. For the entire run, complete nitrification of 99.6% was achieved, which might have been due to wellacclimatized nitrifiers attached in the BioCube media. Specifically, after adaptation, the nitrification continuously increased in the organics removal reactor, even under high residual organics conditions. From the numerous experimental results, the BioCube process seemed to be an effective method for the upgrading and expansion of the existing wastewater treatment plant, with minimum reactor enlargement. [ABSTRACT FROM AUTHOR]

The Kaldnes biomedia K1, which is used in the patented Kaldnes Moving Bed™ biofilm process, has been tested along with other types of biofilm carriers for biological pretreatment of a complex chemical industry wastewater. The main objective of the test was to find a biofilm carrier that could replace the existing suspended carrier media and at the same time increase the capacity of the existing roughing filter-activated sludge plant by 20% or more. At volumetric organic loads of 7.1 kg COD/m³/d the Kaldnes Moving Bed™ process achieved much higher removal rates and much lower effluent concentrations than roughing filters using other carriers. The Kaldnes roughing stage achieved more than 85% removal of organic carbon and more than 90% removal of BOD5 at the tested organic load, which was equivalent to a specific biofilm surface area load of 24 g COD/m²/d. Even for the combined roughing filter-activated sludge process, the Kaldnes carriers outperformed the other carriers, with 98% removal of organic carbon and 99.6% removal of BOD5. The Kaldnes train final effluent concentrations were only 22 mg FOC/L and 7 mg BOD5/L. Based on the successful pilot testing, the full-scale plant was upgraded with Kaldnes Moving Bed™ roughing filters. During normal operation the upgraded plant has easily met the discharge limits of 100 mg COD/L and 50 mg SS/L. For the month of September 2002, with organic loads between 100 and 115% of the design load for the second half of the month, average effluent concentrations were as low as 9 mg FOC/L, 51 mg COD/L and 12 mg SS/L. [ABSTRACT FROM AUTHOR]

The Wilderness Wastewater Treatment Plant (WWTP) located in Orange County, Virginia is a four concentric ring oxidation ditch activated sludge system with a rated capacity of 1,935 m³/day. The three outer rings are used for wastewater treatment and the inner ring is used as an aerobic digester. The flow capacity has been increased from 1,935 to 3,760 m³/d, however, the desired design capacity has since been increased to 3,870 m³/d, and there are plans to eventually expand to approximately 4,840 m³/d with improved nitrogen removal. The design goal for the planned upgrade is to discharge an effluent that contains less than 10 mg/l total nitrogen (TN) at all times, with an annual average of 8 mg/l or less. In this study, the pre-upgrade performance of the Wilderness Wastewater Treatment Plant was evaluated and several modifications were recommended for the incorporation of biological nutrient removal (BNR). [ABSTRACT FROM AUTHOR]

The paper describes the upgrading of an existing conventional two-stage municipal wastewater treatment plant for 200,000 PE to meet the EEC and Slovenian high effluent quality demands for nitrogen. The incoming wastewater is highly loaded with industrial waste and specifically with effluent from anaerobic pretreatment of piggery sludge. The low-cost concept of extensive wastewater treatment is based on integrating appropriate technologies into an existing treatment facility, preserving as much of the technical infrastructure as possible. The proposed concept uses a predenitrification system for the elimination of nitrogen. [ABSTRACT FROM AUTHOR]

Stricter waste quality standards necessitated the upgrading of a large wastewater treatment plant. Taken with constraints on cost and physical space this led to the investigation of a wide range of conventional and unconventional plant configurations that integrate the existing trickling filters to achieve the nutrient removal target. [ABSTRACT FROM AUTHOR]

From 1 January 1995 in The Netherlands 75% of the phosphorus in the influent has to be removed in the waste water treatment plants (wwtp's). At this moment 40 - 50% is reduced by biological incorporation and some chemical dosing. By additional measures an extra 35% reduction has to be accomplished. A further reduction of total nitrogen to 75% has to be realised from 1 January 1998. Further extension of the activated sludge system is not always possible and in most cases rather expensive. Therefore optimization of the existing treatment plant is considered. For this purpose the advanced simulation model STREAM is used. With STREAM almost every waste water treatment plant can be simulated with the computer. In this way, for example, the effect of different control mechanisms and other measures can be studied without costly research. Computer simulation has been applied at the Kralingseveer wwtp of the HH van Schieland (Waterboard in the Netherlands) to optimize aeration control and to evaluate a number of technological process adjustments. Attempts are being made to reduce nitrogen drastically using equipment currently available, supplemented where possible with other limited measures. It can be concluded from the results of simulation, that the use of integrated aeration control, whereby influent flow, and nitrate and ammonium concentrations in the activated sludge are measured on-line, further improves the treatment process. Furthermore, when the sludge content in the aeration tank is raised and nitrogen is removed from the internal return flows, it seems that an average annual effluent quality of 10 mg Ntotal/1 is feasible. Verification of these factors will be carried out in the near future using practical measurements. The Kralingseveer project demonstrates that computer simulation is more than simply a 'game'. It has become a real means of guiding or even limiting the need for extensive and cosily (practical) investigation. [ABSTRACT FROM AUTHOR]

The upgrading and nitrification was a requirement in 1986 for the conventional sewage treatment plant Geiselbullach, west of Munich, Germany, designed for 250 000 inhabitants equivalents. The possibility was tested to use submerged bio-film reactors in the aeration tanks to increase the MLSS concentration. Half-scale experiments were undertaken with three different reactor types. A rope type material, called Ring-lace® was selected for the large-scale application, because it did not produce anaerobic sludge deposits, as the other tested reactor types did. The design criteria had to be developed. The process operation started in January 1988; a few months later the phosphorus removal by chemical precipitation was also put into operation. After stable conditions were assured the concentration of the MLSS could be increased to about 10 g/l, due to sludge volume indices of about 50, formerly 180 to 300. A nearly complete nitrification was achieved, which could even be continued in winter times at water temperatures of 8 to 10 °C. Many highly developed microorganisms in the sessile sludge occurred (nematodes, tubifex…), which grew excessively under certain conditions and reduced the normal bacteria to unacceptable low quantities. A worm cure could reduce the worms to acceptable counts. Problems with the longtime stability of the material arose and were investigated. [ABSTRACT FROM AUTHOR]