Funding:

Project management / project work:

Dr.-Ing. Barbara Wendler, Shambhavi Arvind Kaushik

Situation:

The treatment of drinking water using nanofiltration (NF) and reverse osmosis (RO) is primarily carried out to remove hardness, other inorganic components, natural organic substances as well as trace organics from water introduced by man-made activities.

NF and RO processes produce different quantities of concentrate stream with a correspondingly higher concentration of the separated substances. Antiscalants (predominantly phosphates and carboxylates), which are dosed to avoid precipitation of salt, also remain in the concentrate. All disposal routes for the concentrates (direct or indirect discharge) are part of the plant authorisation and require the approval of the responsible water authorities. In recent years, the discharge of concentrates into a water body has been viewed increasingly critically by the competent licensing authorities, especially when the concentrates contain high concentrations of unnatural anthropogenic trace substances, nutrient salts and / or substances added during the treatment process. Since the refusal of a discharge permit for the concentrates is usually synonymous with withdrawal from the NF/RO process, solutions are required which secure the use of this innovative, energy efficient technology that has many advantages in drinking water treatment in the long term.

In the joint project, KonTriSol, different approaches are being investigated under 7 work packages. The DVGW-Forschungsstelle TUHH coordinates the work package “Antiscalants – assessment and alternatives”, which contains the following sub-goals:

• Reliable evaluation of the effectiveness of the antiscalants in the treatment process by standardized measurement of homogeneous and heterogeneous crystallization
• Reliable declarations on the behaviour of antiscalants used in the preparation process and their evaluation, substantiated with optimised and reliable analysis
• Development, semi-technical implementation and validation of process engineering strategies for the minimisation/avoidance of antiscalants

To this end, laboratory tests on the effectiveness of antiscalants under changing boundary conditions (DOC content, yield, temperature, pH, etc.) are carried out at the DVGW-Forschungsstelle TUHH. Tests for the evaluation of homogeneous scaling in the water phase and heterogeneous scaling on membrane surfaces are applied and further developed and compared with the calculation results from software programs of various membrane and antiscalant manufacturers.

The aim is to develop a reliable and compatible test to assess the efficacy of scaling-inhibiting substances (antiscalants and their ingredients), depending on the respective boundary conditions of the membrane process (pretreatment, water matrix, yield, etc.). This should serve to identify antiscalant products or product mixtures and if necessary, alternative formulations which are retained as completely as possible by the membranes, which can be used in the lowest possible concentrations with as few secondary constituents as possible and which have the least possible impact on the environment when discharged into water bodies.

TECHNION Israel Institut of Technology
Technische Universität Ilmenau
Hamburg Wasser
bbe Moldaenke GmbH

Project management / project work:

Prof. Dr. Mathias Ernst / Dr. Anissa Grieb / Jonas Schuster, M. Sc.

Situation:

Monitoring of organic and biological water quality parameters in water distribution systems (WDS) is usually time-consuming and laborious, making a fast response to anomalies impossible.

This project aims at establishing online monitoring of water quality parameters in real time to rapidly detect and simulate water quality parameters within the WDS and also react to evolving events. This reaction will be automated, thereby diminishing the time between detection and response.

In this project, online sensors for real-time measurements of organic and biological parameters are further developed, tested and evaluated. This includes in particular fluorescence spectroscopy and flow cytometry:

• Fluorescence spectroscopy is evaluated for the characterisation and quantification of dissolved organic carbon (DOC). Concepts for wavelength-specific detectors are developed in cooperation with bbe Moldaenke.
• Flow cytometry is adapted and applied to continuously characterise and quantify bacteria. In parallel, the faster determination of assimilable organic carbon (AOC) by flow cytometry will be investigated as a proxy for bacterial regrowth potential.
• Correlations between parameters measured by fluorescence spectroscopy and flow cytometry as well as to standard drinking water quality parameters are evaluated and analysed.

The simulation of relevant parameters (particles, bacteria, harmful substances) and the development of an algorithm for a rapid anomaly detection as well as the development of automated response to changes, for example disinfectant dose, closing/opening of valves or changing of flow regime, are the work duties of the collaboration partners Technion and TU Ilmenau.

The developed online sensors and simulation results are subsequently explored and validated at a WDS test bed provided by Hamburg Wasser utility.
 

Project management / project work:

Prof. Mathias Ernst, Dr.-Ing. Muhammad Usman

Situation:

Ultrafiltration (UF) membranes are used in water treatment due to their high permeate flux at low pressures and compact size. However, UF membranes suffer from fouling and are not able to remove problematic organic substances as natural organic matter (NOM) from raw water. So far, energy-intensive nanofiltration (NF) membranes are applied to reduce NOM concentrations. A new approach to overcome this problem are electrically conductive ultrafiltration membranes, which have been developed in recent years. They have been mainly used for fouling mitigation and rejection enhancement during filtration of natural organic matter (NOM). Due to the negative surface charge of NOM, a repulsive force is induced when a negative electrical potential is applied to the membrane. In new electrically conductive membranes, positive electrostatic potential is applied to the membrane surface in order to achieve electrosorption of negative charged NOM.

Commercially available porous membranes will be modified in order to generate an electrical conductive surface by coating the membrane (e. q. with an ultra-thin layer of metal or other materials). During dead-end filtration of natural raw water (e.g. ground or surface water) a positive potential will be applied to the membrane surface to enhance the removal of NOM. When electrosorptive removal capacity is exhausted, the applied potential will be reversed to a negative potential in order to desorb the NOM adsorbed on membrane and regenerate it for further electrosorptive filtration. By this, electrosorptive dead-end UF reaches the NOM removal rates of NF membranes, which are frequently operated in cross-flow mode. The Institute of Polymer research of Helmholtz-Zentrum Geesthacht (HZG) is involved in the project.

Funding:

Project coordination:    DVGW-Forschungsstelle TUHH

Project partner:  

• Hamburger Wasserwerke GmbH
• Oldenburgisch-Ostfriesischer Wasserverband
• CERAFILTEC Germany GmbH Blue Filtration
• Umweltbundesamt
• PHL Substratkontor GmbH & Co. KG

Project management / project work:

Dr.-Ing. Barbara Wendler, Charlotte Kast

Situation:

Filter backwash water accrues during water treatment with currently between 1% and 4% of the elevated groundwater. This sludge-containing filter backwash water is usually disposed of as wastewater and is thus lost to the drinking water supply. At the same time, the demand for drinking water is continuously increasing as a result of climate, demographic and structural change. In addition, the iron and manganese-containing filter sludge is often not further recovered.

Appropriate treatment of filter backwash water could on the one hand increase the availability of drinking water for the water supply. On the other hand, the accruing iron and manganese sludge could be further processed for commercial exploitation, e.g., to bind sulphur in biogas plants, but also in agriculture and forestry, the construction industry, and environmental technologies.

In the joint project FITWAS, innovative solutions for the recovery of filter backwash water and the recycling of filter sludge are being investigated with the following objectives:

• Clarification of the suitable process variant (pressure/vacuum filtration, direction of filtration) and membrane modules/materials (ceramic/polymer) for the treatment of filter backwash water and comparison with conventional treatment
• Evaluation of the achievable filtration performance and the derivation of cleaning strategies with minimized use of chemicals and energy requirements
• Legal requirements and determination of the filtrate quality for safe return to the raw water flow to be treated
• Validation of the potential residue utilization depending on the yield and solids content as well as procedural adjustments for the storage of the filter backwash water and treatment of the filter sludge

The DVGW Research Centre TUHH, CERAFILTEC and the UBA will carry out comparative laboratory tests with ceramic and polymer membranes for efficient and reliable recovery of filter backwash water. Subsequent practical trials at selected waterworks from OOWV and HWW serve for implementation in the overall process as well as to generate reliable data on energy and operating costs. At the waterworks of UBA’s test side, the retention of viruses and heavy metals as well as their retention or resuspension are being investigated in particular. The quality and the technical or economic recycling options of the filter sludge are evaluated by PHL. This is intended to create a holistic approach to the reuse of filter backwash water from drinking water treatment, taking into account the legal framework.

Funding:

Project coordination:    DVGW research centre TUHH

Project partner:  

• Politecnico di Milano (IT)
• Kompetenzzentrum Wasser Berlin (DE)
• BioDetection Systems (NL)
• Eurecat - Centre Tecnologic de Catalunya (ES)
• Umweltbundesamt (DE)
• Helmholtz-Zentrum für Umweltforschung (DE)
• Consorci d’Aigües de Tarragona (ES)
• Tutech Innovation GmbH (DE)
• Metropolitana Milanese SPA (IT)
• Multisensor systems (UK)

Project management / project work:

Dr. Anissa Grieb / Jon Wullenweber

Situation:

One focus of SafeCREW will be the investigation of previously unknown disinfection by-products and the further characterisation of already known ones and their formation. With the results, the participating companies intend to develop commercially available methods of quantifying and reducing these by-products so that negative effects on human health can be prevented.

The SafeCREW consortium will use three case studies in northern Germany, Italy and Spain to drive the further characterisation of water quality, and develop new water treatment methods and better management of water distribution networks to maintain high drinking water quality. This will include all processes from source via treatment and up to distribution.

Besides the project coordination, the focus of our research institute within the project is on the chemical-free removal of natural organic matter to prevent formation of disinfection by-products. For this purpose, Ultrafiltration with electro-conductive membranes will be further developed. We are also involved in the development of a passive sampler for pathogen monitoring in water distribution networks and in characterization of natural organic matter.

https://safecrew.org/

https://cordis.europa.eu/project/id/101081980

Follow us: @Safecrew_org or https://www.linkedin.com/showcase/safecrew-org/

Funding:

Project management / project work:

Prof. Mathias Ernst / Natalie Lüdemann

Situation:

Elevated nitrate levels in water bodies, especially in groundwater, are a global problem for drinking water supplies (World Health Organization 2011; Mohseni-Bandpi et al. 2013). Due to its carcinogenic properties and the risk of causing methemoglobinaemia, the recommendations of the World Health Organization (WHO) and the European Economic Community (EEC) are based on a drinking water limit of 50 mg NO3-/l, which is also included in the German Drinking Water Ordinance (TrinkwV; World Health Organization 2011). Various treatment techniques can be used to remove nitrate from drinking water, such as reverse osmosis, ion exchange, electrodialysis and biological denitrification. Biological treatment is increasingly coming into focus, as it offers a high level of water recovery at moderate costs through the complete and selective reduction of nitrate to nitrogen compared to physico-chemical processes (Rezvani et al. 2019).

Biological denitrification can be divided into auto- and heterotrophic denitrification. Heterotrophic denitrification is generally applied in wastewater treatment. Here, readily biodegradable organic carbon sources are needed, which, however, can pose a hygienic risk in drinking water treatment due to accelerated rapid growth of microorganisms. The autotrophic denitrification uses inorganic carbon such as CO2 only, this method is preferable for drinking water treatment, especially for groundwater (Rezvani et al. 2019). In recent years, bioelectrochemical systems (BES) are increasingly discussed with regard to biological denitrification (Cecconet et al. 2018; Rezvani et al. 2019).

The goal of this project is the development of an autotrophic denitrifying bioelectrochemical system for drinking water treatment. The focus is on the search for suitable cathode materials and their shapes, which are able to act as electron donors and suitable habitats for microorganisms. The process will be investigated with respect to its stability, relevant boundary conditions and challenges for implementation.

Initially simple batch tests were designed in order to identify main influencing parameters and optimize the fundamental processes in an innovative reactor setup. Subsequently, this experimental setup is carried out with different electrode materials and varying material properties and shapes. On basis of batch results, a continuous bioelectrical reactor systems shall be constructed.

Funding:

Project management / project work:

Prof. Dr. Mathias Ernst, Muhammad Ismahil

Situation:

Due to climate change, population growth and the increasing pollution of our environment, water scarcity has become a worldwide problem. As an alternative to conventional water treatment plants, membrane-based processes are currently the most effective solution for drinking water filtration, wastewater treatment and industrial energy applications (Abdelrasoul et al., 2020). The versatile membrane separation processes can be used for the removal of organic pollutants, particles, paint, microbes and viruses, as well as for the desalination of seawater (Ang et al. 2015). However, the challenges in membrane technology in terms of fouling behaviour, scaling and energy consumption require research and development to obtain more sustainable membrane applications.

Membrane modelling makes it possible to obtain important information about membrane performance and selectivity. Although the mechanisms of permeation and rejection are complex, a mathematical model allows minimising the number of laboratory experiments required for development, leading to reduced costs and time savings (Ang et al., 2015).

At the Institute of Water Resources and Water Supply, several experimental research projects are being conducted on membrane filtration processes at laboratory and pilot scale. For example, PAN-UF membranes modified with amine groups are being investigated for the removal of oxygen anions from drinking water sources (Glass et al., 2021). Other innovative projects are investigating the electrosorption and desorption behaviour of natural organic substances on conductive membrane surfaces (Mantel et. al., 2021) or examining the treatment of spent filter backwash water using membrane filtration for water recycling in drinking water supplies. One of the challenges in the latter process is the fouling potential that arises on the membrane surface (Kast et. al., 2022).

The goal of this project is to develop a mathematical model that describes the relevant mechanisms in a porous membrane filtration process. Later, the model will be extended to include adsorption behaviour as well as electrostatic sorption and desorption effects. The experimental data collected from ongoing research projects will be used to validate the model.

Funding:

• Behörde für Umwelt, Energie, Klima und Agrarwirtschaft
• DVGW Research Centre TUHH
• EnergieConsult

Project management / project work:

Dr. Anissa Grieb

Situation:

A healthy urban climate requires an adequate amount of greenery on public and private areas, which need
sufficient water supply. In addition to the effects of climate change, population growth is leading to an increased
demand for drinking water - clearly noticeable in the Hamburg metropolitan area. The availability of sustainable
freshwater groundwater is already endangered by conflicts of use and geogenic influences (saline aquifers).
Various adaptation strategies are needed to ensure the long-term supply of drinking water. One starting point is
the increased use of alternative water sources, in particular rainwater, for purposes without requirement for
drinking water quality. At the Bergedorf cemetery, the existing rainwater drainage system is converted into a
management system as part of the RISA (RainInfraStructureAdaption) project, a joint project of BUKEA, Hamburg
Wasser and other partners.

For the conversion of the rainwater drainage system into a rainwater management system, the surface drainage of the paved areas of approximately 2 ha on the 53 ha property is collected in a rainwater storage tank in the future. The storage tank will be installed below the existing rainwater retention basin and filtered rainwater will be fed into the existing water distribution system. The distribution system for water supply at the gravesites will be completely separated from the drinking water network. In case of critical water levels in the tank, an automated replenishment with drinking water will be carried out via a free inlet, so that a permanent supply at the tapping points is guaranteed.

DVGW-TUHH will survey the project with scientific monitoring. For this purpose, the plant will be equipped with measuring technology so that the water inflow, drinking water replenishment and withdrawal are continuously recorded and linked with the climate and weather data. In addition to the system monitoring and electronic measurement data acquisition, regular sampling of the water quality and sedimented solids from the sand trap located in the inlet of the rainwater storage tank will be carried out to compare the collected data with the design approaches.

Funding:

Project management / project work:

Situation:

The use of antiscalants (AS) in the treatment of drinking water by means of  reverse osmosis (RO) or nanofiltration (NF) is common practice in Germany. Various technical products are used in the approx. 90 plants, generally based on phosphonic acid, but also phosphorus-free AS based on polyacrylic acids. The authorised antiscalants are specified in the § 20 list of the Drinking Water Ordinance.

The predecessor project KonTriSol (BMBF/DVGW funding, project end 2023) identified acute problems with the use of AS in membrane filtration. Residual concentrations of antiscalants were found in permeates and drinking water from corresponding systems.

Additionally, problematic substances might be formed in downstream processes such as disinfection or activated carbon filtration from the substances that enter the permeate.. In the case of P-free products, there are indications that the active ingredient content with a small molecular mass is ineffective or can cause biofouling.

Solutions are being sought with regard to the respective product contamination of the AS, human toxicity and operational behaviour.

With the direct involvement of the UBA as a project partner, safe operational, regulatory and legal conditions for Germany are to be derived.

The specific objectives are as follows:

• Further development of analytics for the various types of antiscalants, among other things to clarify the extent of AS transfer into the permeate of the RO/NF
• Simplification of the analysis of AS by developing an "analytical test battery" so that simplified, cost-effective and rapid characterisations can be implemented
• Identification of safe and effective AS formulations (with regard to secondary constituents, membrane permeability, fouling potential in RO/NF, contamination potential in drinking water distribution)
• Investigation of so-called "green" antiscalants (not yet authorised in Germany) with regard to effectiveness and possible side effects
• Proposals for a legally compliant application via the technical regulations of the DVGW (W236) and the § 20 list of the TrinkwV