Taking into account the needs of the waste water infrastructure in Romania, the use of DAUZUC for efficient constructed wetlands (ECW), is an alternative solution to centralized sewage treatment plants, having the following advantages
– low investment and operating costs
– does not require: technical supervision ,maintenance, electricity , chemicals chemical
– the sewerage for waste water collection reduced to the distance between the building and the built wetland
It uses an constructed wetland , defined as a system designed to simulate an natural wetland to treat waste water.
An natural wetland is an reactor with bio–film .
In this bio-reactor has place series of physical, chemical and biological processes in which it participates organisms and microorganisms , plants, soil and sediments accumulated in the lower layer of the area. When the natural soil is remodeled, using layers of natural aggregates and filtration and waterproofing materials but also various related devices , then a constructed wetland is created.
The most used today are wetlands built with vertical discharge with sequential loading . The water is intermittently charged and infiltrated into the substrate, then gradually drains down vertically., and then drains slowly and down vertically to where it is collected to the base via a drainage network. The air re-enters the system at the next loading stage and a high oxygen transfer rate is achieved. For the intermittent vertical discharge, waste water pumps and automation installations are used , and for primary treatment , septic tanks.
At ECW they are not required : waste water pumps, automations, installations primary treatment, being achieved without electricity consumption, all processes mechanical and biological that take place in traditional treatment plants with biological film by using and amplifying natural processes such as: chimney effect, capillary absorption and evapotranspiration.
Although numerous researches have been done regarding the constructed wetlands, it has not been established which types are best for different projects. This is due to the many factors that govern the performance of constructed wetlands..
ECW , reduces the number of these factors only to debit .
It is used an tank with an distributor tubes communicating with the ground surface through absorption tubes and the air exhaust tubes, which ensures. the aeration and pressure necessary to amplify the evaporation due to the natural „chimney” effect. The distributor filter tube has on the lower part of the circumference, slots having the role of filtration, of distribution and of diffusion. The device is placed in a watertight basin made of foil, in a gravel layer , covered with geo-textile membrane, under a soil layer . In addition, at the bottom, the air adsorption and exhaust pipes have gravel washing elements.
When the wastewater enters the tank, the liquid fraction of the waste water enters through the slots directly into the distributor filter tube, then flows on the drain channel located at its base , and is distributed evenly in the gravel layer . In the tank are retained , only the solids larger than 3 mm. • In the tank, the anaerobic digestion of biodegradable materials alternates with the aerobic digestion , depending on the variation of the waste water flow and the load of the built wet area. Aeration is realized by circulation of air between the air adsorption tube and exhaust tube, by the chimney effect , but also due to turbulences created by the falling waste water flow . This influx enriches the content of the aerobic microorganisms. In the tank is performed in the anaerobic phase and denitrification , after nitrification in the gravel layer and the anoxic phase of phosphorus removal . In the gravel layer takes place the aerobic digestion of biodegradable materials by the existing stationary biomedia which, due to the variable flow of waste-water and level variations, is submerged and aerated alternately, each time the level of the distributor filter tube is exceeded by water. The bio-degradation of the organic compounds and the disintegration is continued by the aerobic microorganisms in the topsoil. Treated waste water will be absorbed end and removed by evaporation – transpiration.
