Nitrogen removal in a combined vertical and horizontal subsurface-flow constructed wetland system

WOS: 000270634400046This study was conducted to (1) determine appropriate conditions for nitrogen removal by a combined constructed wetland (CW) system and (2) evaluate the effects of hydraulic loading rate (HLR), nitrogen loading rate (NLR), effluent recirculation, plant uptake, and seasonal change on the removal efficiency of nitrogen. A three-stage experimental CW system consisting of a vertical flow-gravel filtration (v-GF) bed without plants, a horizontal-subsurface flow (h-SSF) bed planted with Iris australis, and a vertical-subsurface flow (v-SSF) bed planted with Phragmites australis in series were fed with primary-treated domestic wastewaters. The beds with plants produced effluents of better quality than the v-GF bed without plants. It was observed that the average removal efficiencies increased as the HLR (from 100 to 30 L/m(2) d) decreased and the recycle ratios (to 100%) increased. The average removal efficiencies in the summer period were found higher of approximately 6% for the v-GF and h-SSF beds and 11% for v-SSF bed. Nitrogen removal by plant uptake was very low and only 3% (Iris) to 7% (Phragmites) of the N-input compared to other mechanisms such as nitrification and denitrification. The volume-base first-order nitrification and denitrification removal constants (1/d) were 0.388 and 0.785 for the h-SSF bed, and 0.412 and 0.293 for the v-SSF bed, respectively

Construction and maintenance cost analyzing of constructed wetland systems

Nowadays, use of constructed wetlands for wastewater treatment especially in rural areas has become increasingly preferable. The most important reason behind this fact is its relatively low investment cost over other treatment options depending on economical conditions of the country. Nonetheless, due to lower operational costs of constructed wetlands than other conventional wastewater treatment systems, investment costs could be regarded secondary as of importance. Investment costs could show differences even at regional scale in a country. Choosing a constructed wetland system among "Subsurface Horizontal Flow", "Subsurface Vertical Flow" or "Free Water Surface Flow"; or designing a hybrid system using concurrent systems plays important role when defining costs of the constructed wetland systems. Due to increasing interest for constructed wetlands since 2003, so many constructed wetland systems have been built in rural parts of Turkey and most of these systems have been designed as horizontal subsurface flow constructed wetland system. As a fact, the cost of horizontal subsurface flow constructed wetlands is comparatively higher than other wetland systems. When different applications in the world are examined, it is observed that mostly horizontal subsurface flow constructed wetland systems are preferred in rural areas. According to the studies within the extent of this work, different constructed wetland types which are built in different regions of Turkey and their expected and realized costs are analyzed and compared with other countries. Moreover, operational costs have been calculated. Consequently, a work to be taken as reference for further scientific studies has been prepared with presented wetland analyses which could be used by especially decision makers and researchers. © IWA Publishing 2011

Construction and maintenance cost analyzing of constructed wetland systems

Nowadays, use of constructed wetlands for wastewater treatment especially in rural areas has become increasingly preferable. The most important reason behind this fact is its relatively low investment cost over other treatment options depending on economical conditions of the country. Nonetheless, due to lower operational costs of constructed wetlands than other conventional wastewater treatment systems, investment costs could be regarded secondary as of importance. Investment costs could show differences even at regional scale in a country. Choosing a constructed wetland system among “Subsurface Horizontal Flow”, “Subsurface Vertical Flow” or “Free Water Surface Flow”; or designing a hybrid system using concurrent systems plays important role when defining costs of the constructed wetland systems. Due to increasing interest for constructed wetlands since 2003, so many constructed wetland systems have been built in rural parts of Turkey and most of these systems have been designed as horizontal subsurface flow constructed wetland system. As a fact, the cost of horizontal subsurface flow constructed wetlands is comparatively higher than other wetland systems. When different applications in the world are examined, it is observed that mostly horizontal subsurface flow constructed wetland systems are preferred in rural areas. According to the studies within the extent of this work, different constructed wetland types which are built in different regions of Turkey and their expected and realized costs are analyzed and compared with other countries. Moreover, operational costs have been calculated. Consequently, a work to be taken as reference for further scientific studies has been prepared with presented wetland analyses which could be used by especially decision makers and researchers.</jats:p

Organic Matter and Nutrient Removal Performance of Horizontal Subsurface Flow Constructed Wetlands Planted with Phragmite karka and Vetiveria zizanioide for Treating Municipal Wastewater

Three pilot horizontal subsurface flow constructed wetlands (HSSFCWs) were constructed, covered with a geomembrane and filled with gravel media. The study compared the performance of the three pilot HSSFCWs, two planted with Vetiveria zizanioide and Phragmite karka, and one without plants, and all containing aeration facilities in treating municipal wastewater. HSSFCWs were loaded at a hydraulic loading rate of 0.025 m/d and a maximum organic loading rate of 6.16 g BOD/m(2)d with a hydraulic retention time of 6 days. Results show that V. zizanioide had better removal efficiencies (TSS: 92.3%; BOD5: 92.0%; PO43-: 86.7%) than P. karka (TSS: 91.3%; BOD5: 90.5%; PO43-: 85.6%), whereas P. karka showed better removal efficiency of NH4+ (86%), NO3- (81.8%) and SO42- (91.7%) than V. zizanioide (NH4+: 83.4%; NO3-: 81.3%; SO42-: 90.5%). Removal rates in unplanted CWs were lower for all parameters: TSS (78%), BOD5 (73%), NH4+ (61.0%), NO3- (55.5%), PO43(67.6%), SO42- (78.1%). Higher removals of total coliform (3 log units) and Escherichia coli (2.4 log units) were obtained in the HSSFCW with plants compared to unplanted units (total coliform: 1.9 log units; Escherichia coli: 1.2 log units). Based on these findings, the treated water can be directly disposed into surface water bodies or used for irrigation as the concentrations of the pollutants are below the standard permissible limits of effluent discharge set by EEPA and WHO. Therefore, both V. zizanioide and P. karka are good candidates for remediation of wastewater by a constructed wetland system