Hybrid system for wastewater treatment in multifunctional wetlands - A case study at UNIVATES in Lajeado, RS, Brazil

Sammanfattning: Abstract Centro Universitaire UNIVATES is located in the town Lajeado that is situated in the most southerly state, Rio Grande Do Sul, in Brazil. The university has 5000 students, teachers and others staff. UNIVATES is not satisfied with their present wastewater situation and wants to improve it by eliminate the smell caused by the wastewater. They would also like to remove the oil that the storm water brings into the wetland. The high amount of particles in the storm water gives rise to a lot of sediments that eventually will fill up the wetland, and something has to be done about this, if the wetland should continue to be in use. Another aspect to consider is the wish of some people at UNIVATES, for the wetland to be a beautiful and recreational place. All these factors had to be considered, which led to the main question: How can the use of the wetland for wastewater treatment be combined with the request for the wetland to be a beautiful place with the wildlife preserved? During the course Wetland Technology that we took before our departure to Brazil, we got introduced to the situation at UNIVATES by Professor André Jasper and Odorico Konrad who visited the course several times. They pointed out that the main issue is the smell from the wastewater and later during the field study at UNIVATES, more information were obtained through discussions, meetings and conversations with the people involved. Several visual inspections were carried out by walking around the wetland. We could determine where and how the inlets and outlets to the wetland were and when it was clear which inlets that brought wastewater and which that brought storm water, the water flow of the wastewater was estimated. Water samples from the wetland were collected at five different sites and analyses of pH, BOD, COD, N-Tot, phosphorus and metals were done by the accredited laboratory at UNIVATES. To test some of our theories, we did a smaller practical experiment that got the name Superficial Filtration Bed. The results from the water samples showed the highest BOD, COD, N-Tot and Phosphorus levels in the samples from site 2 and 4 and this reveals that it is wastewater. This was also confirmed by the smell that we felt at these sites during the visual inspections. The results also showed that there is no wastewater coming from site 1, 3 and 5. Our final proposal is to create a multifunctional wetland with the purpose to take care of both storm water and wastewater and at the same time work as a research and recreational area. The wetland, which would be divided into two parts, will constitute of all the fundamental functions; storm water buffering, sedimentation basin and biological oil separation and treatment. There will also be research sites and hybrid system for wastewater treatment. The hybrid system will consist of two steps where the first is aerobic and the second both aerobic and anaerobic. The first step is a Superficial Filtration Bed (SFB) and the second a FWS wetland. The conclusion of this thesis is that more detailed research is needed to be able to dimension the specific functions correctly. With some further investigations the proposal presented is possible to carry through and our feeling when we left UNIVATES was that the people responsible really liked our ideas. They made it clear that they want to make a change and improve the situation and with the help they have gotten from us, they are a few steps closer to solving the problem.