Summary:

Ensuring water supply and sewage management are among the primary tasks of every commune, and they are also the condition for multi-functional de-velopment of rural areas. Positive changes in the area of providing communes with the basic water mains-sewerage infrastructure mean an improvement in the living conditions for the population and for the functioning of companies. For many years intensive work has been going on in Poland, aimed at ensuring a suitable status of the environment, especially in rural areas where still a lot needs to be done in this respect. At the end of the 20th and the beginning of the 21st centuries numerous water supply and sewerage systems have been built in those areas, as well as many household and collective sewage treatment plants. One of the provinces where the largest number of household sewage treatment systems have been built is the Lublin Province. The technological most frequently applied here include systems based on the use of a septic tank and filtration drainage, systems with a biological bed or active sludge, as well as hybrid systems (biological bed + active sludge). Less popular, on the other hand, are constructed wetland systems, probably because their construction requires plots with a larger area. However, for about 50 years such systems have been successfully used in numerous countries of Europe and on other continents. Experience accumulated so far on the functioning of constructed wetlands indicate that such objects are characterised with simple operation and maintenance, and notable tolerance to non-uniform inflow of sewage. Also, the costs of installation of those systems are comparable to those involved in the construction of conventional sewage treatment systems.
For a long time constructed wetlands have been the object of studies at numerous research centres in the world and in Poland, and still there is ongoing search for technological solutions permitting high effectiveness of elimination of pollutants, and of biogenic compounds in particular. Also rather scarce still are studies on the efficiency of sewage treatment in constructed wetland systems over multi-year periods of their operation. Therefore the author of this work decided to address this subject and performed a study in this field.
The primary objective of the study was analysis of the results of 11 and
10-year research projects concerned with the efficiency of elimination of pollutants from domestic sewage in to single-stage constructed wetland systems with horizontal and vertical flow, with willow Salix viminalis L. (object No. 1, HF type) and with common reed Phragmites australis Cav. Trin. Ex Steud. (object No. 2, VF type), as well as of the results of similar several-year studies conducted at two multi-stage (hybrid) constructed wetland systems (object No. 3 - configuration I of the HF-VF type and configuration II of the VF-HF type, and object No. 4, VF-HF type). The sewage treatment systems under study are situated in the territory of the Lublin Province, in the localities of Jastków, Sobieszyn, Dąbrowica and Janów near Garbów, and the technological solutions employed there differ in the amounts of sewage treated and in the method of its flow in the systems (VF - vertical flow, HF - horizontal flow), in the number and size of beds, in the kind of vegetation (willow and reed), and also in the volume of beds with limestone.
The functioning of the multi-stage systems was analysed primarily with
a view to determine the optimum configuration of soil-plant beds that would ensure the achievement of the highest possible effects of removal of the basic pollution in-dicators and biogenic compounds.
In three of the objects under analysis experiments were performed on the use of beds with limestone in order to increase the efficiency of phosphorus elimination. Within the scope of the study also the amounts and composition of raw sewage were determined, and an estimation of the efficiency of pollutant elimination in septic tanks was performed. Also, experiments were conducted with the aim of determination of changes in selected physicochemical properties of material filling the beds of constructed wetland systems during their multi-year operation, and analyses were performed concerning the productivity of plants growing on the beds, and their selected chemical properties.
Based on the studies it was found that during multi-year operation the sin-gle-stage constructed wetlands of types VF and HF ensured total suspended solids removal efficiency at the level of ca. 65%, and the effects of reduction of BOD5 and COD were in the range of 78-85%. Those objects were less efficient in terms of removal of biogenic compounds - nitrogen and phosphorus. Whereas, particularly high effects of removal of the basic pollution indicators (above 90%) were observed in the hybrid constructed wetland systems with willow and reed, with VF-HF bed configuration (with vertical and horizontal flow). Moreover, those objects ensured ca. 65% efficiency of removal of total nitrogen and 85-95% effectiveness of elimination of total phosphorus. Based on the statistical analysis performed, in the hybrid systems no significant effect of low temperatures was noted during the autumn-winter seasons that would cause a reduction of the effectiveness of pollution removal. The single stage VF type system proved to be less resistant to low temperatures. Moreover, the statistical analysis revealed that hybrid systems of the VF-HF and HF-VF types are characterised by very high - 99% - reliability of operation. During the period of the study, for over 361 days in a year the systems met the specific requirements concerning the quality of treated sewage in terms of TSS, BOD5 and COD. Lower reliability was characteristic of the single-stage con-structed wetland systems, especially of the VF type.
The results obtained indicate that single-stage constructed wetland systems can be used on a larger scale in rural areas with scattered housing structure. Hy-brid systems, on the other hand, can be applied successfully at recreational centres or in protected areas where, for aesthetic and landscape reasons, the construction of conventional sewage treatment plants is not usually welcome.
The results presented herein can find a practical application, in the design and construction of highly effective sewage treatment systems, as well as in projects of upgrading existing systems with the aim of optimising their operation. The results and observations presented in this dissertation can be made available to all investors have begun are at the stage of beginning to solve their problems with water supply and sewage management within their territories, through the con-struction of either household sewage treatment plants or small collective sewage treatment facilities.