Digital greywater recycling as an integral part of new commercial and residential construction

Complete systems ready for connection from 5.4 to 97m³/day.


Up to 65 % of the water demand is used for personal hygiene, such as showering, bathing, washing hands and for the washing machine. The resulting wastewater is the so-called grey water. This water has a relatively low level of pollution and, after appropriate treatment, can be ideally reused for flushing toilets, washing laundry and watering the garden.

With a new series of ready-to-connect greywater systems and impressive international references, the water expert INTEWA from Aachen shows that this form of water reuse has long since found its way into new commercial and residential buildings. The technology has now been tested for over 10 years in hundreds of plants worldwide. The treated water meets the strict parameters of NSF-350 Type C (Commercial). This makes it the only system in the world that has been certified according to this standard. The water is treated by means of biological degradation followed by patented ultrafiltration. The new series is designed for large systems with a grey water demand of more than 5,400 litres per day. This corresponds to the grey water produced by 100 people from showers, bathtubs and washbasins. What is new is that such systems are equipped with automatic cleaning. In this way, the costs for ultrafiltration can be significantly reduced and, depending on the water price and size, the system can achieve payback periods of well under 5 years. With the newly developed I-CONNECT control system, the system can be remotely maintained, remotely controlled and optimised during operation. This drastically reduces maintenance costs and increases functional reliability. Systems of this kind can be used in residential, hotel and office construction or wherever large quantities of grey water are produced.

Ready-to-connect systems with indoor tanks

Greywater harvesting systems have a huge savings potential with a very small space requirement. The required storage volume corresponds approximately to the daily greywater demand. This storage volume can often be accommodated in the building's installation room. Special indoor tanks are suitable for this purpose, which can be coupled and expanded as a modular battery. The advantage is that these systems can be pre-produced in the factory ready for connection. This facilitates planning and installation. The following two systems show an example of a complete system ready for connection and the space required for the treatment of 5,400 litres and 21,600 litres of grey water per day.

I-CONNECT control technology and automatic chemical cleaning

The heart of every greywater system is the control system. The internet-compatible I-CONNECT control technology was developed especially for the new greywater series for commercial use. This centrally controls the entire system with all components, such as the permeate pumps, backwash pumps, cleaning valves, drinking water make-up and automatic chemical cleaning, right up to the pressure boosting system. Offline, the controls can be operated via a touch screen, depending on the version. The new I-CONNECT control technology is produced in CE design for the European market and UL design for the US market. Three AQUALOOP membrane stations, each with six membrane cartridges of 5,400 litres of greywater per day (a total of 16,200 l/day), can be connected to a central controller. The system is expanded by means of expansion modules via a BUS cable. In turn, 3 membrane stations can be connected to each expansion module, etc. Systems with a greywater demand of more than 32,400 litres per day can be delivered with a central pump unit and only one controller.

The I-CONNECT control technology enables chemical cleaning of the membrane cartridges to be carried out automatically. The average volume flow of the ultrafiltration membranes can thus be tripled and the efficiency of the filtration process increased. The desired cleaning interval can be set via the touch screen. The entire cleaning process consists of acid cleaning with citric acid, which dissolves inorganic compounds (scaling) in the membrane and the pipes. In addition, there is oxidative cleaning with chlorine. Due to the biological processes in the bioreactor, biofouling occurs in and on the membrane. Organic blockages can be removed by using chlorine. From a plant size of 5,400 litres per day, the investment for this technology pays for itself within a few years.

I-CONNECT web portal and app

Online access to the respective system is via the I-CONNECT web portal or the I-CONNECT app. The web portal provides access to all linked I-CONNECT systems. In connection with the I-CONNECT licences, the systems can either be viewed online (Licence Viewer) or actively accessed and controlled online (Licence Expert). With the browser version, long-term monitoring and evaluations are also possible via automatic data storage. The I-CONNECT app enables access and operation of the systems via smartphone or tablet.

Compared to other systems, the connection between controller and cloud server does not require port forwarding or VPN. A direct, multi-encrypted connection is established via LAN. Access via app and web browser is via an encrypted HTTPS connection (security certificate). The data is hosted on secure IONOS 1&1 servers in Europe. The controller allows output to common BMS (building management systems), such as Bacnet.

The greywater system of the future can thus be controlled from anywhere. Reading consumption and statistics as well as optimising the system parameters with recommendations for maintenance are just a few tangible benefits that this technology is expected to bring. For large buildings, integration into the local building management system is possible via the already integrated interfaces. This significantly optimises the operating and maintenance costs and contributes to further optimising the economic efficiency of the systems.


Demo access I-CONNECT greywater system Aachen

On the website you can log into the greywater demo system at INTEWA via a free access. After logging in and selecting the relevant system, the user is taken to the clear "system overview" with the current operating states, fill levels, flow rates and much more.

Under Settings, the system can be configured for both the central unit and the expansion modules. This is normally only carried out once during commissioning with possible support from the INTEWA experts. During online maintenance, components can also be tested via this menu.

The timer menu allows you to set the running times of various components, such as the fan running time. When the system is delivered, these values are preset with "default" values to facilitate commissioning. Online commissioning is also possible with the help of I-CONNECT.

Virtual visit 5,400 litre demo greywater system with 360° tour

The demo system of a 5,400-litre greywater system in the INTEWA premises can be visited virtually at this link. Especially in times as dominated by personal contact restrictions and home offices as these, a virtual visit not only saves money but also time. When you enter the site, you will first find yourself in the entrance room of the INTEWA building. Here you will find the systems for the treatment of drinking water from rainwater, for the treatment of wastewater from the small sewage treatment plant and for the irrigation of the green roof. Leave these systems to the right and walk past the I-CONNECT stormwater management demo system. If you open the door to the left of this, you will come to the greywater demo system. You can even go inside the system using the arrow at the top left. The arrow to the right of the plant takes you to the chemical cleaning, the blowers and the pressure boosting system

Example system: Rancho Cienega Sports Complex in Los Angeles

The first example highlights the Rancho Cienega Sports Complex in Los Angeles. As one of the largest facilities for baseball, basketball, football, softball, swimming, tennis and much more in the USA, the company attaches great importance to guaranteeing its guests a safe, varied and, above all, pleasant stay. Therefore, the topic sustainability is also important here. With an AQUALOOP greywater complete system, approx. 5,400 litres of treated shower water are recycled daily for toilet flushing and irrigation of the sports facilities. In this way, costs can be saved in the long term, which can be invested in better and more varied activities for young and old.

Example system: Camping Gerhardhof in Austria

Another example of the new INTEWA "packaged solution" is the Gerhardhof in Wildermieming, Austria. This place for relaxing holidays uses a wide variety of measures to offer its guests a relaxing but at the same time sustainable stay. The approach of the three founders is quite simple: use as much of the resources that are already there and at the same time interfere as little as possible with the surrounding environment. In addition to their own spring, the rainwater is collected in a service water pond and is used for irrigation. In addition, the existing grey water from showers and hand-washing basins is collected and reused for flushing toilets. With 400 to 500 visitors at a time, up to 6,000 litres of water can be saved per day.

Summary and outlook

The fact that greywater must not be left unused has now been accepted by experts. With the new series of ready-to-connect greywater systems, the water expert INTEWA from Aachen shows that this form of water reuse has now reached the highest technological level in modern building technology and has long since found its way into new commercial and residential buildings. With ready-to-connect systems with bigger than 5,400 litres of greywater production per day, automatic cleaning and an internet-enabled control concept, the systems can be remotely maintained and controlled worldwide. This drastically reduces maintenance costs and increases functional reliability. With total costs of approx. 150 T€ for a system that treats 20 m³ of greywater per day, amortisation periods of less than 4.1 years can be achieved at approx. 5.00 € drinking and wastewater costs / m³. This means that greywater recycling systems are no longer only of interest for "green buildings", but should become standard for every larger residential, hotel and office building.


Dipl. Ing. Oliver Ringelstein


Auf der Hüls 182

52068 Aachen

Phone: 0241-96605-0

Author: Oliver Ringelstein, INTEWA GmbH

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Virtual visit of the 5,400 litre demo grey water system with 360° tour

Basic knowledge of water treatment

Free online planning tools

Reference projects



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