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FACTA UNIVERSITATIS Series: Architecture and Civil Engineering Vol. 7, No 1, 2009, pp. 65 - 82 DOI: 10.2298/FUACE0901065N
WETLANDS, CONTRUCTED WETLANDS AND THEIR'S ROLE IN WASTEWATER TREATMENT WITH PRINCIPLES AND
EXAMPLES OF USING IT IN SERBIA
Vladimir Nikoli1, Dragan Milievi2, Slobodan Milenkovi2
1Erasmus Mundus Stipendist, Euroaquae E-mail: email@example.com 2University of Nis, The Faculty of Civil Engineering and Architecture, Serbia
Abstract. Wetlands protection programs, as a relative new approach in surface water and ground-water protection The types of Wetlands, their's mechanism of removal nutrients and other pollutants from water are shown in this work paper. Wetland restoration, the renewal of natural and historical wetlands that have been lost or degraded, is a growing activity. Constructed wetlands, as treatment systems that use natural processes, are very adequate and highly efficient, low cost way in wastewater treatment for small communities, point pollution sources, depending, of course on conditions and adequate land spaces near those places. Some examples from Serbia of this way and approach are shown.
Key words: Waste water treatment, Wetlands, Constructed wetlands, Macrobiological methods.
Long regarded as Wastelands, Wetlands are now recognized as important features in the Landscape that provide numerous beneficial services for people and for fish and wildlife. Wetlands are among the most productive ecosystems in the world, comparable to rain forests and coral reefs. They provide great volumes of food that attract many animal species.
2. WHAT ARE WETLANDS?
Even though there are many different terms for description of the wetland systems, the most widely accepted definition was developed by the International Union for the Con-servation of Nature and Natural Resources (IUCN) in the Ramsar Convention, in 1980. According to this convention, wetlands were defined as "any areas of swamp, pond, peat, or water, natural or artificial, permanent or temporary, stagnant or flowing water, includ-
Received September 15, 2009
V. NIKOLI, D. MILIEVI, S. MILENKOVI 66
ing estuaries and marine water, the depth of which at low tide does not exceed 6 meters." (Mitsch and Gosselink, 1993).
Wetlands, other than peat bogs, are highly productive systems and support high biodi-versity. Like other ecosystems, wetlands also perform many ecological functions. The hy-drological, biological and biogeochemical functions impart them various values (Sather and Smith, 1984). Some of the values of these wetlands given by Vymazal et. al (1998) and Denny (1997) are summarized below: water quality functions and water quality im-provements, hydrological and hydraulic functions, climatic effects, biodiversity functions, energy production, educational uses, recreational and reclamation uses.
All Wetlands freshwater or salt have one characteristic in common: the presence of surface or near surface water, at least periodically. The hydrology of Wetlands is generally one of slow flows and either shallow or saturated substrates. The slow flows and shallow water depths allow sediments to settle as the water passes through the Wetland. The slow flow also provides prolonged contact time between the water and the surface within the Wetland. The complex mass of organic and inorganic materials and the diverse opportunities for gas/water interchanges foster a diverse community of microorganisms that break down or transform a wide variety of substances.
Wetlands perform many functions that are beneficial to both humans and wildlife. One of the most important is water filtration. As water flows through a Wetland, it slows down and many of the suspended solids become trapped by vegetation and settled out. Other pollutants are transformed to less soluble forms taken up by plants or become inactive. Wetland plants also foster the necessary conditions for microorganisms to live there. Through a series of complex processes, these microorganisms also transform and remove pollutants from the water. Nutrients, such as nitrogen and phosphorus, are deposited into wetlands from storm water runoff, from areas where fertilizers or manure have been ap-plied and from leaking septic fields. These excess nutrients are often absorbed by Wet-land soils and taken up by the plants and microorganisms. For example, Wetland mi-crobes can convert organic nitrogen into useable, inorganic forms (NO3 and NH4) that are necessary for plant growth and into the gasses that escape to the atmosphere.
Wetland processes: water retains more days sedimentation its cleaned by plants and microorganisms
reduction of nitrogen, phosphorus substances, heavy metals and other toxic compounds and bacteria
plants under the surface of device provide oxygen
an area rich with oxygen is created around the roots
cleaning is effective
Fig. 1 How wetlands work
Wetlands, Contructed Wetlands and their's Role in Wastewater Treatment... 67
Wetlands are one of the most valuable and fragile components of a watershed, but for many years they were filled and drained for agriculture and development. Now we are learning that wetlands are crucial to the health of our waters and wildlife. Wetland resto-ration, the renewal of natural and historical wetlands that have been lost or degraded, is a growing activity. It can improve water quality and wildlife habitat across the world. When high concentration of nutrients enter water as a result of human activities, often occurs Hypoxia. Hypoxia is the condition in which dissolved oxygen is below the level necessary to sustain most animal life. For many members of aquatic community, hypoxia is like drowning, because life giving dissolved oxygen levels in a body of water drop much lower than normal.
There is growing interest and expertise in the field of Wetland restoration. This trend is a good news for hypoxia affected waters since some Wetlands can significantly reduce the amount of nutrients reaching our inland and coastal waters. Restoring the lost and de-graded Wetlands to their natural state is essential to ensure the health of watersheds. Restoration is a complex process that requires expertise, resources, and commitment from many different stakeholders. All restoration projects require planning, implementation, monitoring and management. Many projects require a team with expertise in ecology, hy-drology, engineering, and environmental planning. Getting local experts and community involved gives the project local ownership, which is important for restoration success.
Nutrient removals from several specific natural wetlands projects are presented in Table 1.
Table 1. Nutrient removals from several specific natural wetlands projects
4. CONSTRUCTED WETLANDS FOR WASTEWATER TREATMENT
As a result of the exponentially increasing demands of human expansion and resource exploitation, it has been recognized that natural wetland ecosystems cannot always func-tion efficiently for desired objectives and stringent water quality standards. These and many other factors have led to the rapid development of "constructed wetlands" for wastewater treatment (Wetzel, 1993).
Because natural systems can improve water quality and filter pollutants from water that flows through on its way to receiving lakes, streams and oceans, engineers and scien-
V. NIKOLI, D. MILIEVI, S. MILENKOVI 68
tists construct system that replicate the functions of natural wetlands. So, Constructed wetland treatment systems are engineered systems that have been designed and con-structed to utilize the natural processes involving wetland vegetation, soils, and their as-sociated microbial assemblages to assist in treating wastewater. They are designed to take advantage of many of the processes that occur in natural wetlands, but do so within a more controlled environment. Synonymous terms to constructed include manmade, engi-neered or artificial wetlands.
What Constructed Wetlands can provide: water quality improvement flood storage and the desynchronization of storm rainfall and surface runoff cycling of nutrients and other materials habitat for fish and wildlife passive recreation, such as bird watching and photography active recreation, such as hunting education and research aesthetics and landscape enhancement
When properly designed, constructed wetlands offer a number of advantages, includ-ing low cost, simplicity of operation, and effective removal of BOD5 and TSS (table 2). When sized adequately, constructed wetlands are also tolerant of fluctuating flows and variable water quality.
Constructed wetland treatment is constrained by a number of limitations, including relatively large land requirements and a degree of uncertainty not found in more conven-tional approaches (table. 2).
Table 2. Advantages and limitations of constructed wetland treatment of domestic wastewater
Excellent removal of BOD5 and TSS Good removal of nutrients, depending on system design Ability to handle daily or seasonally variable loads Low energy and maintenance requirements Simplicity of operation
Variable treatment efficiencies due to the effects of season and weather Uncertainty as to treatment effectiveness under all conditions Sensitivity to high ammonia levels Larger land area requirement than for conventional treatment Potential for mosquito production
The use of constructed wetlands for sewage treatment at different levels is commonly well known. However, they have also been applied for the treatment purpose of different types of wastewater.