Tjaša Griessler Bulc
In its long history, nature has developed intense self-cleaning and buffering capacities. In the context of ecological sanitation and sustainable water management, the application of technologies that mimic healthy natural ecosystems became vital. These technologies aim to close the loop and return resources back to the source. Their basic characteristics, which can be utilised and further improved, are their high buffer and self-protective capacity as well as the provision of habitat diversity. Moreover, these systems have the remediation ability, provide a high level of biodiversity and higher stability of ecosystems. Ecosystem technologies comprise methods of protection and restoration of the environment through natural ecosystem processes. The establishment of ecosystem technologies offers sustainable solutions that contribute to the flood and drought management, preservation of biodiversity, pollution reduction, and enable nutrient recycling. The functions of ecosystem technologies are based on aquatic, waterside, wetland as well as terrestrial ecosystems’ characteristics, such as high flood prevention, water retention capacity, biodiversity as well as specific physical, chemical and biological processes for the reduction of diverse pollutants.
By applying ecosystem technologies, a local community or even a small society can play a significant role. In the context of our contemporary environment, it is important to bring sustainability to local communities or to a household level. Pollution originating from local communities should be treated with the use of ecosystem technologies. They should be seen as prophylactic and therapeutic measures to overcome local environmental problems. Ecosystem technologies include alleviation and adaptation of local communities at a time when climate change system and global changes affect common life in local communities. They could represent an innovative approach towards nature, space and environment protection based upon system thinking or, in other words, a holistic approach involving technologies aimed at regional and local community levels.
Multi-functionality of ecosystem technologies is considered as follows:
Ecosystem technologies for water management merges vegetated drainage ditches, waste stabilization ponds and stormwater detention ponds, treatment wetlands, buffer zones, phytoremediation with dense woodland establishment, river revitalization, and in stream and bank side river techniques. One of the main aims of ecosystem technologies concept is to integrate exchange, combine and use multi-functionality of different kind of “green technologies” to obtain innovative and sustainable solutions for environmental protection and restoration.
Drainage networks of surface and subsurface drains primarily serve to remove and store excess water associated with irrigation and storm events. In the agricultural areas they help to remove surface water ponding and lower water tables below the major rooting zone for optimum plant production and therefore representing integral components for sustaining the economic growth. Nonetheless, drainage networks affect several hundred thousand hectares of land throughout western and Eastern Europe, leading to loss of retention capacity, loss of biodiversity and water purification.
Although the amount of new drainage in Europe declined during the 1990s, the existing drainage programmes continue to exert a negative impact on the environment. Therefore, management of vegetated drainage ditches is an important issue in drainage pollution control. In the past, the value and the function of a network of ditches have been generally ignored and drainage ditches were the forgotten links between land and aquatic receiving systems.
Now it is understood that such ecosystems maintain environmental quality and support immense biodiversity, including threatened species of flora and fauna as well as having important recreational and aesthetic qualities.
Waste stabilization ponds are simple man-made basins for primary, secondary and tertiary treatment of variety of wastewaters. They are used worldwide, alone or in combination with other treatment processes. Waste stabilization ponds are low cost treatment technology with simple operation and maintenance.
Anaerobic, facultative and maturation ponds are constructed in one or several series. Anaerobic ponds are designed for primary treatment. They remove suspended solids and some of the soluble element of organic matter. Most of the remaining organic matter is removed in a facultative pond by algae and heterotrophic bacteria. Tertiary treatment takes place in maturation pond where pathogens and nutrients are removed.
Detention ponds are open water bodies for the retention of stormwater runoff from urban, agricultural and other areas. The stormwater treatment facility must be flexible to manage high flow rates of the runoff followed by dry periods, and high pollutant concentrations in the first flush followed by diluted concentrations in the main flow. Stormwater detention ponds are diverse biological systems with a high buffering capacity that enable water detention, minimize the hydraulic peaks and reduce the pollutant input in downstream facilities and/or receiving waters. Detained and treated water can be used for different purposes or discharged to the environment.
Different plant species can appear in detention ponds: at the shallower marginal areas emergent and in deeper parts floating and submerged species. The treatment processes in wet detention ponds are similar to those occurring in natural smaller lakes and pools: e.g. sedimentation, adsorption, conversions and degradation of biodegradable compounds by microorganisms and uptake of pollutants by plants.
Among those, the key mechanism for pollutants removal in detention ponds is sedimentation. Since the main removal mechanism in wet detention ponds is sedimentation, the wet detention ponds generally have high efficiency in particulate matter removal. Organic matter is subdued to microbial and macroinvertebrate decomposition and final transformation to inorganic matter in the sediment, where it is stored.
Photo: Griessler Bulc, 2002.
Photo: Griessler Bulc, 2002.
Treatment wetlands are technically and economically feasible solutions for the treatment of different wastewater types. The technology is widespread around the world. Already ten years ago, more than 5.000 treatment wetlands were operational in Europe. The performance is thoroughly documented and the systems are capable of reducing the concentration of target pollutants by different bacteriological, physical and chemical processes to acceptable levels before discharging to the environment and therefore mitigating the harmful effect that the disposal of untreated wastewater may have.
Treatment wetlands imitate natural wetlands by using an array of natural processes to transform and remove the contaminants and as such they represent important part of ecosystem technologies. Compared to their natural counterpart, these processes are intensified. This is achieved with appropriate design, filling material, planting, and incorporation of technical equipment (pumps, aeration, pre-treatment) which ensures optimal utilization of the treatment wetlands area and volume. As treatment wetlands typically require less or no supplemental energy, their operational costs can be approximately two orders of magnitude lower than those of a standard three-stage wastewater treatment plants. The treatment wetlands removal efficiency usually assessed by the decrease in biochemical and chemical oxygen demand, total suspended solids and nutrient load has already been studied widely. Treatment wetlands can also effectively remove a wide array of persistent pollutants such as pathogens, trace organic contaminants and heavy metals, which all have a negative influence if released into the environment. Treatment wetlands have been used as a treatment step before wastewater is reused in agriculture, but with very variable success. Although wetlands are effective for the treatment of wastewaters, the ever-changing reality of more stringent discharge regulations by the local governments imply that the wastewater treatment systems have to meet high water quality standards before discharge.
Tjaša Griessler Bulc1,2, Aleksandra Krivograd Klemenčič1,2, Boris Kompare2
1Faculty of Health Sciences, University of Ljubljana
2Faculty of Civil and Geodetic Engineering, University of Ljubljana
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