Unlike many other countries, Norway is not confronted with water shortages – but it does have a strong appreciation of the need to conserve resources and protect the environment.

This has led to a focus on concepts such as ‘ecological sanitation systems’ whereby graywater is treated and reused, and blackwater from the toilet is separated at the source so that it can be transformed into valuable resources such as fertilizers, soil conditioners and bio-energy.

Prof Petter Jenssen of the Norwegian University of Life Sciences (UMB), believes that in future completely decentralized wastewater treatment systems will be common in urban areas.

“Graywater from sinks, showers and the laundry will be treated locally in compact low-maintenance systems that constitute attractive landscape elements, and these systems can coexist with decentralized water supply,” he says.

“In the Oslo suburb of Klosterenga, an experimental decentralized urban treatment system that processes graywater from 33 apartments has consistently produced swimming-water quality. An advanced nature-based treatment system is located in the courtyard of the building and consists of a septic tank from where graywater is pumped to a vertical down-flow single-pass aerobic biofilter, followed by a sub-surface horizontal-flow porous media filter.

“The effluent has consistently been better than the World Health Organization drinking water requirement of 10mg/L for nitrogen, and in relation to bacteria, faecal coliforms have been in the range of zero to 10/100ml. The small area required for the system and the high quality of effluent enables a range of urban reuse options, including discharge to wetlands or streams, irrigation and groundwater recharge, as well as domestic uses such as toilet flushing and car washing.”

UMB, in collaboration with the Ecomotive company, has developed a compact plant to treat graywater from recreational dwellings, cabins and cottages. According to Jostein Grevsgard of Ecomotive, the system is designed to treat up to 1,000L of graywater a day, and for larger requirements several units can be connected in parallel.

“The system consists of two sections that fit together to form a unit with a total diameter of 1.85m by 1.55m high, which includes a septic tank,” he says.

“A small pump in the septic tank distributes graywater over a biofilter in the top section so that it percolates down to the bottom section where it passes through two more filters before being used for soil irrigation or another appropriate purpose.

“All filters in the unit consist of lightweight clay aggregates and similar porous media – no chemical additions are needed in the purification process. The most distinctive aspect of the system is how compact it is, which means it is very cost effective and can be installed in a small area.

“Ecomotive has begun manufacturing the units and there are plans to market the system in a package that will include the Jets toilet system. The Ecomotive graywater system is related to the Jets toilet system in several ways. First, the Jets vacuum toilet reduces the amount of water needed for toilet flushing, as it uses less than one litre per flush. This significant reduction complements the strategy of the Ecomotive company in developing compact systems that facilitate water saving by recycling treated graywater.