Wastewater treatment in constructed wetlands and their cost analysis

In our day and age the rise in numbers of our population is concurrently rising with the amout of water we need and thus our natural water sources are on the decrease. It gets harder and harder to obtain drinking and domestic water. Additionally, releasing domestic wastewater into the enviorment without fully puryfing it or at least partitially cleansing it, so that the harmful pollutants are kept to a minimum is adding to the enviornmental pollution and at the same time it is affecting the wildlife. The aim of this thesis is to recycle most of the used domestic water in order for it to be used again by the population and to construct constructed wetland areas, instead of using portable treatment plants, in rural areas in order to purify the wastewater with natural methods. It is said that constructed wetland areas are financially more advantageous and economic in the construction and operation compared to portable treatment plants. The importance of the wastewater treament for the wildlife is mentioned in the introduction. Waste water samples from all over the world and in Turkey have been examined and the advantages and disadvantages of the said samples have been mentioned. This section deals with the history of constructed wetland areas. Additionally a wide-range of literature research about the comparision of different methods of wastewater treatment has been conducted. Some of the applications of constructed wetland areas in Turkey have been adressed. In the second section the effects of water treatment plants on the environment, social-economic structures and the health of the population have been explained. The Environment Influence Assesment (ÇED) and the Social Influence Assement (SED) reports, that are used to help to determine the type of wastewater treament plant to be constructed through establishing possible issues in the construction and the operation beforehand, are evaluated. The third section deals with the different methods of wastewater treament and compares their operational and econmic factors. This section mentions the conventional wastewater treatment in cities, portable treatment systems, natural wastewater treament methods that are used in rural areas (underground wastewater drainage ponds, spilling the wastewater on sloping areas, wastewater distillation ponds, stabilization ponds and wastewater treatment through the use of constructed wetlands) and touches on the criteria that are needed in the choice of a wastewater treatment method. The technical specifications and the characteristics in the application phases of the wastewater treatment methods have been explained. The fourth section deals with the main topic of this thesis, the constructed wetland areas, that consist of two different categories: Sub-surface flow and Free surface flow. Some of the issues that can be encountered during the construction of the constructed wetlands like the clogging of the filtering (filling) material, underground leakage, faulty vegetation planting, faulty operation/management, inadequate maintenance have been mentioned and possible solutions have been proposed. Imagery of the constructed wastelands have been presented. The properties of plant species that can be used in constructed wetlands have been listed. The factors for the design of the constructed wetlands have been elaborated on. (site selection, topography, ground, use of the terrain, the nutrition and the need for a pumping mehchanism, ground isolation, climate, overflow control, calculation of the constructed wasteland's surface areas, depth, the choice and composition of the filling material, the entrance and exit constructions of the constructed wetlands) The method of how to physically filter and which constructions are needed to do so, in a constructed wetland, have been stated. The elements that serve as waste disposal mechanisms in the constructed wetlands and the needed ratio of their occurence have all been elaborated on. The needed elements are as follow: suspended solid(AKM), biochemical oxygen demand (BOİ5), organic material removal, nitrogen, phosphor, pathogen, toxin, heavy metal removal. A cost analysis for the constructed wetlands has been conducted. In the fifth part the town of Alpullu (KIRKLARELİ) (the application area of the thesis) has been introduced. The settlement, history, social and economic factors, the town's geography, the culture and tourism, the general climate properties of the region, the geological structure, the topographic structure, probable effects of seismic activity, the map and town planning and drinking water and the sewer system network have been mentioned. Technical Information about the conventional wastewater treatment plant (500m3/a day) constructed by the İller bank for this town has been given. The target values, within the parameters of this project, for the purification with the waste disposal mechanisms (BOİ5, AKM, nitrogen, phosphor) have been stated. The estimated population of Alpullu town in 2051 has been calculated with various calculation methods (İller bank, arithmetical increase method, exponential increase method) and the Iller bank method that is accepted throughout Turkey has been chosen. The flow rate and the waste loads that go into the wastewater treament have been calculated with reffering to the Iller bank specifications and the wastewater treatment design parameters have been determined. The bill of quantities has been calculated for a conventional wastewater treatment in Alpullu, basing it on the the units that will be built for the wastewater treament plant. While building the portable water treatment plants for Alpullu it was projected that 4 times 200m3/a day packages of purification would be needed and the costs for these have been calculated. Additionally, if a natural wasterwater treatment (a constructed wetland) would be chosen, the bill of quantities would already have been calculated. The comparison of the results of the 3 different wastewater treament methods show that the constructed wetland method is cost efficient, the operation is easier and the yield is higher Finally in the last part of the study it has been stated that the constructed wetlands, that are not only more economical in the construction and the operation, need to spread in rural, less populated areas.