Verification and assessment of technologies for tertiary treatment of municipal wastewater
During April excursions for a broad public will be held at wastewater treatment Brno-Modřice. For more information and reservation see the website of Brněnské vodárny a kanalizace, a.s. (http://www.bvk.cz/zakaznikum/aktuality/dulezita-upozorneni)
The project LIFE2Water was presented at the fair Veletrh Věda Výzkum Inovace (www.vvvi.cz).
Water pollution represents a significant risk to water environment such as acute and chronic aquatic toxicity, accumulation in water ecosystems and loss of habitats and biodiversity as well as threads to public health. Wastewater treatment plants represent an important source of pollution. Organic pollution, nutrients, pathogenic organisms and other substances with negative effects on organisms are discharged with treated wastewater. Among the last ones, pharmaceuticals, personal care products, pesticides and other chemical substances used for industrial production can be mentioned. Removal of such pollution is complicated yet important to decrease the negative effects on aquatic ecosystems.
Project LIFE2Water aims to improve the quality of discharged effluents. The goal of the project is to implement innovative technologies for tertiary treatment of municipal wastewater with a significant potential for improvement of effluent quality and their verification on the pilot scale with the aim to contribute to the achievement of good ecological status of aquatic ecosystems. Within the project, three pilot plants will be designed and constructed: (1) pilot plant based on micro-strainer filtration in combination with UV radiation; (2) pilot plant for ozone sonolysis and (3) pilot ultrafiltration plant. Pilot plants will be placed to the municipal wastewater treatment plant for long-term testing, verification and optimization of technologies for tertiary treatment of municipal wastewater. Technologies will be evaluated from economic, environmental and operational perspective. A set of procedures for selection of the technology for tertiary treatment of municipal wastewater will be developed. This tool will support water companies and other water management experts in selection of an appropriate technology for tertiary treatment stages. Sub-goal of the project is to increase awareness among the target groups through selected dissemination activities. Firstly, the aim is to involve experts in the field of wastewater management, analytical and environmental chemistry to exchange knowledge, share experiences and to show examples of best practice for removal of hazardous substances and other pollution to the aquatic environments. Secondly, the aim is to involve general public to increase awareness about the need for elimination of water pollution and protection of aquatic environment.
Project LIFE2Water aims to improve the quality of discharged effluents. Within the LIFE2Water project, innovative technologies for tertiary treatment of municipal wastewater with a significant potential for removal of microbial contamination and removal of selected industrial substances, pesticides and pharmaceuticals will be verified and assessed.
Due to relatively long period of time between preparation of the project proposal and start of the project relevant legislation in water management will be updated. Methodology for sampling of wastewater and methodology for determining concentration of selected priority substances will be prepared.
This action will be followed by actions focusing on the design and construction of the pilot plants. Pilot plant based on micro-strainer filtration in combination with, pilot plant for sonolysis of ozone and pilot ultrafiltration plant will be designed and constructed. They will be located at the wastewater treatment plant Brno-Modřice. Each of the plants will be tested for one year under various operating conditions (flow, load, seasonal differences). Depending on the operational conditions pilot plants will be optimised with the aim to reduce operating costs and to achieve required effluent quality in terms of selected priority substance removal and microbial contamination elimination. Consumption of electricity and other necessary inputs (e. g. consumption of oxygen and chemicals) will be monitored and measured. Wastewater samples will be regularly taken and analyzed using appropriate analytical methods. Basic and microbial parameters and concentration of selected priority substances will be monitored. Assessment and comparison of tested technologies in terms of economic, environmental and operational aspects will be prepared. A set of procedures for selection of the technology for tertiary treatment of municipal wastewater will be developed. The focus will be given to the environmental protection and economic sustainability.
Emphasis will be given to dissemination activities. The aim is to promote the project and its results, to exchange experiences and to show best practises examples. Dissemination activities will be focused on different target groups of the project. Website with information about the project, notice boards and leaflets for general public as well as experts will be created. Excursions to the wastewater treatment plant Brno-Modřice for general public as well as experts will be organised. The project results will be presented at conferences and in expert journals. Focus will be put on networking, exchanging information, sharing experiences and showing best practice examples with experts from water management.
Expected results of the project are verification and assessment of selected technologies for tertiary treatment of municipal wastewater in a pilot scale. Selected technologies will be evaluated and compared in terms of pollutant removal efficiency, economic efficiency (investment and operating costs) and possible scale-up. A set of procedures for selection of the technology for tertiary treatment of municipal wastewater will be developed. Three pilot plants for tertiary treatment will be designed and constructed: (1) pilot plant based on micro-strainer filtration in combination with UV radiation; (2) pilot plant for ozone sonolysis and (3) pilot ultrafiltration plant. During the project implementation achievable removal efficiency and operating parameters will be tested, verified and assessed. Focus will be given to the decrease of consumption of electricity and other inputs.
Significant expected result will be the achievement of desired removal efficiency of the selected technologies at different operating conditions at wastewater treatment plant. Removal efficiency of the following pollutants will be monitored and assesed:
(1) Removal rate of monitored priority substances
(2) Elimination of microbial contamination (Fecal coliform bacteria, Enterococci and Escherichia coli).
Important results of the project will be the involvement of target groups through dissemination activities. Important results will also involve support of implementation of the European legislation in the field of water management.
Pilot plants will be located at the municipal wastewater treatment plant in Brno-Modřice. The wastewater treatment plant in Modřice treats wastewater conveyed by a system of sanitary sewers from the city of Brno and by a system of pumping stations from the wide surroundings of Brno.
Raw wastewater is conveyed to the wastewater treatment plant (WWTP) via an inlet structure used as a flow split. Water coming to the WWTP is pre-treated and freed from coarse gravel in a gravel trap and then it passes mechanically scraped screens with slot width of 6 mm. Screenings from the screens are pressed and then flushed with water. Water flows from the screenings room by gravity to an aerated sand trap equipped with grease separation. The sand is further processed in a sand classifier and washer and then stored in a skip. Water coming from the gravel trap and the sand trap is conveyed by a channel to a screw pumping station. Water is pumped to a flow split dividing the flow into six primary clarifiers. The primary clarifiers ensure mechanical removal of settleable particles.
After the mechanical treatment, the wastewater is conveyed to an intermediate pumping station and it is further pumped into activation. The activation is divided into two lines, each with two separate lanes that can be operated separately or together. Water is first conveyed to the anaerobic tank (phosphorus removal), then to a circulatory anoxic serving for pre-denitrification. The last stage of activation is an anoxic part with fine-bubble aeration divided into aerated and unaerated zones. Return sludge from the secondary clarifiers is freed from nitrates by denitrification in the pre-anoxic zone located in the first part of the activation in order to achieve efficient phosphorus removal. Phosphorus removal ensured primarily by the biological process or by dosing ferric sulphate. The mixed liquor from the activation tanks is fed into six secondary clarifiers where activated sludge is settled and separated. Settled sludge is conveyed via a return sludge pumping station to the pre-anoxic zone of the activation. Activated excess sludge taken from the activation is processed in the sludge management.
Sludge management consists of a primary sludge thickener, flotation thickener for the biological sludge, mechanical screens, homogenisation tank, digesters, digested sludge storage tanks, sludge dewatering plant and sludge drier. Primary sludge from the primary clarifiers is thickened and mixed with the excess activated slubdge in the homogenisation tank. Mixed raw sludge is pumped to the digesters. Tenperature in the digestors is kept at 35°C. The sludge retention time in the digesters is about 22 days. Produced biogas is stored in two two diuble-membrane gas holders and is used for electricity and heat generation in cogeneration units. Before drying, digested sludge stored in storage tanks is dewatered in centrifuges. Dewatered sludge is dried in a paddle sludge drier. Long sludge retention time (over three hours) combined with the average sludge temperature of 100°C enables pasteurisation and sanitary treatment of sludge.
AQUA PROCON s.r.o.
Palackého tř. 12, 612 00 Brno
Brněnské vodárny a kanalizace, a.s.
Hybešova 254/16, 657 33 Brno
ALS Czech Republic, s.r.o.
Na Harfě 336/9, 190 00 Praha 9