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Early pollutant warning system for sewage plants

In June 2012, the Baden-Württemberg Ministry of the Environment, Climate Protection and Energy Sector presented a report on the contamination of water bodies with micropollutants, including drug residues and toiletry and detergent additives which make their way down the drain and into wastewater systems. Technologies that can help identify pollutants in the wastewater treated in sewage plants are urgently needed. LimCo International GmbH might have a solution. The Konstanz-based company has developed a fully-automated early warning system for monitoring the quality of water and sediment in sewage plants and waterworks. In contrast to previous systems, LimCo’s biomonitor is based on non-optical methods. The project has been nominated for the NEO 2012 Innovation Award of the Karlsruhe TechnologyRegion under the heading “water” in the environmental technologies category.

The EU Water Framework Directive (WDF) commits all member states to achieving good ecological and chemical status of all water bodies by 2015. Toxic substances that enter water bodies can generate risks for human health and the environment. These substances enter the human body through inefficiently treated drinking water and through the food chain, for example the consumption of seafood. Effective interventions to identify potentially toxic substances early on in the wastewater treatment process are needed to ensure the long-term sustainable supply of clean water and prevent harm to health and the environment.

Active biological wastewater monitoring aims to identify acute maximum pollutant levels or fluctuations in the cleaning performance of wastewater treatment plants. This can be achieved with the Multispecies Freshwater Biomonitor© (MFB) developed by the Konstanz-based company LimCo International GmbH, a system that combines biological and chemical online measurements. In contrast to the majority of existing biomonitors, LimCo’s MFB is not based on optical methods such as video recordings, fluorescence and bioluminescence measurements. Such methods have a decisive disadvantage: “They cannot be used in water that is turbid, rich in particles or coloured,” says Dr. Almut Gerhardt, Managing Director of LimCo International explaining that the use of optical methods requires untreated water to be filtered. Filtration removes particle-bound pollutants with the result that any potential toxicity is already reduced before the test is applied. “The non-optical method can be used for a broad range of applications; it can be used in all different types of media, including turbid water, sediments and soil,” says Dr. Gerhardt. LimCo’s method therefore avoids erroneous results due to filtration, and ensures that the quantity of harmful substances contained in the water is not underestimated.

Animals that spin webs and freshwater shrimp as indicators

The PC unit is used for recording and analysing measurement data. © LimCo International GmbH

The biological online monitoring of surface waters commonly involves the use of invertebrate organisms, bacteria and algae as indicator species. LimCo International GmbH’s technology relies primarily on aquatic organisms as they are able take up dissolved as well as particle-bound pollutants. “These organisms enable us to assess and evaluate the overall level of pollution,” says Dr. Gerhardt. In addition, discharge from sewage plants usually contains a large quantity of particles consisting of bacterial biomass and the pollutants and nutrients bound to it. This is why so-called particle feeders - filterers (e.g. net-spinning caddisflies), fine-particle feeders (e.g. non-biting midges) and coarse-particle feeders/shredders (e.g. gammarids, if the pollutant level is not too high) - are frequently found in waterways into which treated water is discharged. 

Gammarids primarily feed on coarse organic material, but do also feed on other food sources such as algae and invertebrate organisms. Gammarids play a crucial role in the substance cycle of flowing waters and are important prey organisms of fish and aquatic birds. Gammarids are used as water quality grade II indicators, which is the level of water quality the EU Water Framework Directive is seeking to achieve for flowing waters. “The organisms’ lifespan of approximately one year is long enough for them to develop and indicate chronic effects at even low pollutant levels,” Dr. Gerhardt explains.

Continuous evaluation of ecotoxicological discharge in water

Hazardous incident: a high level of pollutants occurring during the biomonitoring process leads to the animals’ reduced activity and death (red bar). © LimCo International GmbH
LimCo’s biomonitor consists of measurement chambers of variable sizes and designs, a measurement device and a PC unit to record and analyse measurement data. Specific software registers, calculates and indicates significant alterations in the behaviour and survival of indicator animals in the measurement chambers. “We measure the animals’ movements in a weak and harmless electrical field and therefore do not depend on optical sensors,” says Gerhardt. This method is suitable for monitoring aquatic animals (from daphnia that are around 3 mm in size to fish of around 30 cm). Different behaviour, e.g. flight, stress-related ventilation, inactivity and death, is recorded and analysed. These data are subsequently compared with the chemical parameters (e.g. nitrate and ammonium content) of the sewage plant. The MFB has primarily been used for the ecotoxicological evaluation of surface waters, mining wastewater and communal and industrial wastewater as well as drinking water, both in the laboratory and in the field. “The MFB is the only biomonitor worldwide that can be used for all kinds of media and all kinds of animals and with such a high number of replicates,” Dr. Gerhardt says explaining that the biomonitor is able to simultaneously monitor three indicator species of 16 individuals each, thus ensuring early warning and optimal protection of water bodies.

Recurrent alarm due to toxic load

Mounts for MFB chambers © LimCo International GmbH

The biological early warning system was used in the state-of-the-art Limmattal wastewater treatment plant near Zurich, Switzerland, and the continuous biological and ecotoxicological monitoring of water quality was successfully tested and installed. A total of seven test runs of between two and three weeks each were carried out using wastewater from the Limmattal wastewater treatment plant. The gammarids and hydropsychids survived for a period of between one and three weeks. The initial low oxygen content in the wastewater was subsequently optimised. “The abrupt death of the animals within only a few weeks suggests that the wastewater was highly polluted,” Dr. Gerhardt says, assuming that compounds such as polyacrylamide and diclofenac were responsible for the death of the animals. Road salts with peak conductivity values and unknown pollutants might also account for the deaths. When a warning is issued, it is crucial to make a detailed comparison of the data with online analytics data in order to identify the concrete cause of death. The company therefore plans to combine biological early-warning systems with chemical analytics. 

Optimisation of the technology

The experiments carried out with the MFB have also given the inventors ideas on how to further optimise the method. The plan is to equip the MFG device with a direct hardware output in order to provide real-time access to data on the central computer as well as to directly and simultaneously compare the data with chemical online data. In addition, the company also plans to use and test less sensitive animal species for their suitability in sewage sludge monitoring (e.g. non-biting midges). 

LimCo International GmbH worked with the University of Stuttgart’s ISWA (Institute for Sanitary Engineering, Water Quality and Solid Waste) within the framework of a degree thesis that focused on using the MFB for testing numerous wastewater-relevant pollutants. “The use of the MFB is not limited to specific sewage plants; it can also be used to monitor subsequent tertiary purification steps, including ozonisation and activated charcoal powder filtration. These applications are currently being tested and evaluated. As things stand at the moment, the MFB is of relevance for all wastewater treatment plants in Baden-Württemberg,” explains Dr. Gerhardt.

The latest report by the Baden-Württemberg Ministry of the Environment found that new technologies and analysis systems for the identification of micropollutants during the wastewater purification process are in great demand. According to information from the Ministry, the current difficulty is that there is only limited data available about the effect many substances have on the environment. In addition, micropollutants are a relatively new field in ecological and chemical water treatment and suitable solutions still need to be found.

Dr. Almut Gerhardt
LimCo International GmbH
Technologiezentrum Konstanz
Blarerstr. 56
78462 Konstanz
Tel.: +49 (0)7531/ 99 13 594


Website address: https://www.biooekonomie-bw.de/en/articles/news/early-pollutant-warning-system-for-sewage-plants