There are lots of drains that are not connected to municipal wastewater treatment plants. Only in Sweden, there are 700,000 private wastewater drains, of which 60 percent are for homes and vacation cabins. Many of the cabins are located near waterways and lack water purification or have malfunctioning treatment systems. This contributes to the eutrophication of lakes and seas.
Another problem is that bacteria can leach out and contaminate groundwater. According to the Environmental Protection Agency 350,000 of the private sewers need to be replaced or improved. The corresponding statistics are not available for the rest of Europe, but it is plausible that millions of drainage systems do not meet the EU’s basic demands for treatment.
“We have developed a system for wastewater treatment based on how nature breaks down organic matter and takes care of nitrogen and phosphorus compounds,” says Yngve Svensson, CEO at Alnarp Clean Water Technology. “There are several treatment options on the market, such as septic tanks or solutions based on purification by using various chemical substances (a mini treatment plant). In both cases you get a sludge that must be disposed of regularly. Our cleaning system is simple and does not require extensive infrastructure. It is based on natural processes with efficient sludge digestion. We call the purification system ACT Natural TM and apply the fundamental belief that the sludge should be viewed as a resource and not as a problem.”
How to ACT Natural
Wastewater from normal households consists mainly of faeces and urine, and water from showers, dishwashers and washing machines – a mixture of organic matter, nutrients (nitrogen and phosphorus), water and bacteria. Wastewater may also contain residues of drugs, metals from pipes and other pollutants that should not get washed down the drain.
The purification processes in ACT Natural™ consists of two main steps called ProACT respectively InterACT. If the environment has special requirements for additional phosphorus removal, the process can be supplemented by a third purification step (ReACT™).
In practice, the ACT Natural™ process two is buried in the garden. The tanks are two meters in diameter and two meters high, which means that they can accommodate 6 m3 of sludge and water. The first tank is completely concealed under the ground while the other tank protrudes slightly above the ground with plants growing in it.
- With ProACT™, pretreated wastewater by organic matter is decomposed by microorganisms in an oxygen-free environment. The result of the process is an aqueous slurry mixture that is pumped away for further degradation in InterACT™. Up to 100 litres per hour can be pumped from the first to the second tank.
- InterACT™ is a combination of microorganisms and a bed of plants that contribute to the purification. Plant roots take up nutrients from the water and gradually grow. To stimulate growth oxygenated water is circulated in the tank. The water forms an aquatic ecosystem in the garden for insects, butterflies, frogs and where other animals can interact. Some of the water from the InterACT™ is pumped back to ProACT™ to increase the microbial process (denitrification ) that converts the water-soluble nitrogen compounds to gaseous substances.
“It takes about 10 days for the wastewater to pass through the tanks and out comes clean water. The only thing you see in the garden when the system is installed is that the plants are watered,” says Svensson. “We use water plants as cattails, reeds, in InterACT™. The plants in the test facility in Alnarp are two meters high and must be cut down every year.”
“We like to compare it to a stream in the forest that is 20 km-long in your garden. It is the natural treatment processes that we recreate – the constant movement of water, oxygen, natural microorganisms from water, plant roots in interaction with plants that handle contaminants and nutrients in a functioning ecosystem. If the availability of nutrients is good there is the opportunity for more luxuriant plants and the same applies to the microorganisms that adapt. One can say that the treatment is self-regulating,” says Svensson.
ACT Natural™ is tested by the Institute for Agricultural and Environmental Engineering (JTI) in Uppsala and treatment characteristics were found to be good. The water is odourless, content of organic matter (BOD) was low and it could be used for watering the garden.
One of the advantages that Alnarp Clean Water Technology emphasizes is that there will be no sludge. “At our test facility in Alnarp, we have charged the system with the same amount of sewage as a normal household with four people producing for more than 15 years. We have been able to do without a single sludge removal. Other advantages are that the power consumption of the pumps is low, that no chemicals need to be added and that the system basically runs itself,” concludes Svensson.
Recycling of phosphorus
Are the waters in the vicinity of the property classified as sensitive to the environmental authorities to require additional treatment of phosphorus? In such circumstances even ReACT™ binds phosphorus to a natural adsorbent lime material. This involves the use of a slow and passive process that takes two to four years before the cup becomes saturated with phosphorus. It can then be removed and used as a soil conditioner that contains both nutrients and contributes to the higher pH of the soil. When the cleaning process done, at least 90 percent of the phosphorus is bound to the lime material.
The article was published in December 2014