A next generation of circular economy water systems and services
4 June, 2050
Waste water source
In Nordehnham there is a wastewater treatment pilot plant operated by community workers from ‘Stadtwerke Nordehnham’. The system treats municipal wastewater with a Dissolved Organic Carbon rating of 11 mg/l and a conductivity of 1,240 µS/cm.
The water is distributed with pipes from the reclamation facility to the fields.
In addition, the biological quality parameters are sufficient so the water can be used for irrigation of non-food plants. (e.g. fibre plants and energy crops). Furthermore, the reclaimed water would be usable for the irrigation of food crops according to the hygienic requirements in the EU.
Waste water treatment description
Nutrient removal : Conventional WTTP techniques (not the goal of the project)
Pesticide removal : UV disinfection
Disinfection : Ultrafiltration, Activated carbon & UV disinfection:
The water undergoes the UF process (like the water type 1) but additionally is treated with an activated carbon filter. The granulated activated carbon (GAC, grain diameter 0.6 to 2.4 mm) has a large inner surface which is suitable for the adsorption of organic components in the water, such as e.g. pharmaceuticals and pesticides. Furthermore, GAC is also a carrier material for microorganisms and therefore facilitates the further removal of biodegradable organic substances from the water. If there is manganese in the influent, a manganese removal filter (sand) should be used in addition to prevent damages through the sedimentation of manganese. A downstream disinfection with UV-light after the activated carbon filter enhances the microbiological safety of the service water. You will find more details about the procedure in our factsheet about the activated carbon filtration.
Suspended solids removal : Prefiltration & Ultrafiltration
Other : Monitoring is done by flow cytometry
Flow cytometry is used for quick determination of micro biology and growth potential in the water. Next to the determination of the number of total and intact cells that represent the actual microbiological state of a water sample, flow cytometry also allows the determination of the growth potential. For this purpose, water samples are collected in sampling vessels. Bacterial concentrations are measured on day 0 (= actual state) and after seven days of incubation at a temperature similar to the ambient temperature the water is typically exposed to (for MULTIReUse a temperature of about 22 ± 1 °C was chosen). This procedure and an example of a result are shown in the next figure
Exemplary flow cytometry density diagram of a bacterial suspension with living/ intact membrane cells (in red-dotted area), resp. with dead damaged membrane cells (outside of the dotted area) after colouration with two dyes; SYBR green and propidium iodide. Every dot stands for a bacterium. Under the fluorescence microscope living/intact bacteria appear in green and dead/damaged bacteria in red.
As for other water types, flow cytometry offers fast and reliable determination of bacterial cell numbers in the field of monitoring water reuse processes. Based on the fact that the detection isn’t based on the cultivation of the bacteria, the entire bacterial population in the water is measured independent of their growth requirements. While traditional hygienic indicator bacteria such as coliforms, intestinal enterococci or clostridium perfringens are typically not detectable after membrane filtration and total colony counts are only available after 2–3 days, flow cytometry offers a sound data base for the microbiological assessment of the efficiency of different water treatment steps. Information about the actual microbiological status of a water sample, i.e. about the total and intact cell concentration, is supplemented by information about the microbiological growth potential and therefore indirectly about the assimilable organic nutrients contained in the water. The method is compatible with the ‘Hazard analysis and critical control points‘ (HACCP) concept as the rapid detection of changes in the microbiology provides a good basis for process control decisions.
For further information please read: https://water-multi-reuse.org/en/portfolio/monitoring-procedures/
The pilot plant in Nordehnham achieves a capacity of 5.6 m³/h for the treatment with UF. The effluent is used to irrigate agricultural fields explained before.
Treated wastewater is usually unsuitable for the use in agriculture or industry. MULTI-ReUse closes this gap through the development and implementation of new processes for the reuse of water. The aim of the project is the development, demonstration and evaluation of a modular water treatment system, in order to offer service water in different qualities and volumes for the different purposes and to competitive prices.
For further scientific results please read: https://water-multi-reuse.org/en/results/
Water reuse for agricultural purposes is not regulated by German or EU law yet. However, there are some recommendations (e.g. US-EPA, FAO, WHO) and legal guidelines (e.g. water framework directive, groundwater and urban waste water treatment directive), where relevant aspects for water reuse for agricultural purposes are defined. A European regulation is going to be released soon to standardize the quality requirements. Water reuse for agricultural purposes is getting more and more important because of rising water demand due to agricultural intensification and climate change effects. It is assumed that treated wastewater will increasingly be considered an important resource in arid and semi-arid developing and industrialized countries in order to safeguard agricultural yields. In addition, competitive pressure regarding water abstractions will rise between agriculture, industry and drinking water production. Water reuse can release that pressure on water resources. The MULTI-ReUse quality criteria contribute to that.
Derived hygienic quality requirements for water reuse for agricultural purposes