<p>The amount of various phosphorus (P) fractions in the sediment and the relationship between the amount of P and sediment particle size were investigated in a constructed wetland southwest of Linköping. Furthermore, the possible correlation between clay content in the sediment and distance from the inlet was investigated. Sediment samples were collected along three transects from the inlet to the outlet, with six samples in each transect. In order to measure the soluble P, an NH4Cl extraction was done. This was also analysed for total soluble P after oxidation with peroxodisulphate. The sediment was also analysed for total-P and organic P by drying, dispersion in a mortar and sieving followed by boiling in HCl. Analysis of phosphate-P in all extracts was done with an acid molybdate solution and ascorbic acid, forming a blue complex that was measured spectrophotometrically. There was no significant relationship between soluble P or soluble total-P and the proportion of clay in the sediment samples. This was also the case for total-P and organic-P. Generally, the levels of phosphorus in the sediment were low, which may result from too deep sediment samples, causing the settled P-rich sediment to be diluted by the terrestrial soil underneath the wetland. There was a low proportion of clay in the sediment (4 – 18 %), which made it difficult to detect any correlation with soluble-P content. When omitting the samples at the inlet (which were more influenced by vegetation than the others), a significant positive correlation between percentage of clay and distance from the inlet was detected, suggesting that clay particles were settling in the wetland.</p>

Thesis (M.A. (Psychology))--North-West University, Potchefstroom Campus, 2008.

The amount of various phosphorus (P) fractions in the sediment and the relationship between the amount of P and sediment particle size were investigated in a constructed wetland southwest of Linköping. Furthermore, the possible correlation between clay content in the sediment and distance from the inlet was investigated. Sediment samples were collected along three transects from the inlet to the outlet, with six samples in each transect. In order to measure the soluble P, an NH4Cl extraction was done. This was also analysed for total soluble P after oxidation with peroxodisulphate. The sediment was also analysed for total-P and organic P by drying, dispersion in a mortar and sieving followed by boiling in HCl. Analysis of phosphate-P in all extracts was done with an acid molybdate solution and ascorbic acid, forming a blue complex that was measured spectrophotometrically. There was no significant relationship between soluble P or soluble total-P and the proportion of clay in the sediment samples. This was also the case for total-P and organic-P. Generally, the levels of phosphorus in the sediment were low, which may result from too deep sediment samples, causing the settled P-rich sediment to be diluted by the terrestrial soil underneath the wetland. There was a low proportion of clay in the sediment (4 – 18 %), which made it difficult to detect any correlation with soluble-P content. When omitting the samples at the inlet (which were more influenced by vegetation than the others), a significant positive correlation between percentage of clay and distance from the inlet was detected, suggesting that clay particles were settling in the wetland.

This research is based on the plan and design of Datang constructed wetland as a storm water wetland system. Qantity of the discharges from Datan community drainage system including its branches surround Dapeng Bay National Scenic Area are estimated. The objectives of this research is to study the possibilities of using the concept of stormwater wetland system for including the Datan constructed wetland and Lin-Bian right-bank wetland as flood detention wetland system and treatment wetlands during the dry season. Generally, flood detention ponds are not functioning except during storm seasons. Rainfall are mostly concentrated from June to September in southern Taiwan (mainly due to southwest monsoon and typhoon), the Datan wetland has therefore planned to treat the domestic sewages and the disposal from aquaculture farms during the dry season, and first flushing drainage during storm season. Besides the flood detention volume, Datan wetland has been designed into four major sections, a) primary settling for settle part of the suspended particles and aeration; b) bio-filtration through 2 sets of bio-filter using crushed bricks and oyster shells as filter media, mainly designed for BOD removal and partly early denitrification; c) followed by shallow weeds pond for reaeration and nutrients uptake by plantation; d) entering a series of open water ponds for stabilization. Landscape has been take good care for recreative function and habitat reserved for variety of birds. Due to the flood detention function will flood the basin few times a year, variable depth environment and plantations are designed. Wetland maintains ordinary water level at EL=-1.1m, maximum flood detention can go as high as EL=+1.5m. The wetland has effective surface approximately 5.5 ha., maximum flood detention quantity approximately 130,000 cubic meters. Since the area is tidally affected, influents contain different levels of salinities. Plantation becomes a difficult issue for the Datan wetland, due to the saline waters. Mangrove is the best choice, so far, for this situation. The mangrove forest has the richest productivity on wetland ecosystem, and can carry on the physical biology multistage degeneration to the sewage and absorb various pollutants. Hydraulic analysis estimates the peak discharge of Datan drainage system¡¦s 10 year flood frequency is 20.17cms, Datan constructed wetland and Linbian right bank constructed wetland can reduces the peak rate of 8.06cms and 4.38 cms, respectively. In addition, most of the branches of the Datan drainage system are thus achieve the ten year return period bench mark from the HEC-RAS evaluation The water quality monitoring results after one month of operation have shown the average elimination rates, TOC=-10%, BOD5=53%, TKN=71%, NH3-N=88%, NO3-N=65, NO2-N=90%, TN=70%, TP=52%, OP=56%, Chl.a=-61%, SS=4%, the turbidity (NTU)=70%. BOD and nutrients are shown effective reductions, while the SS and the chlorophyll-a are correlated mainly due to the plankton growth in the open waters. Long-term monitoring is continuing for the evaluation of the water quality purification function and the operational management model.

Graduation date: 1994

The risk of the Iraq’s marshlands disappearing is still high unless serious measures are adopted. Sewage discharge and irrigation-water pressure, compounded by the effects of climate changes and the extent of the planned dam construction in upstream countries, make this event more likely. Most of the marshlands’ inhabitants (Marsh Arabs) are suffering from lack of access to safe, clean water and lack of sanitation and are reluctant to look for better places to live and work. Constructed wetlands are among the best alternatives to solve their problems. The application of constructed wetlands to meet more stringent standards for wastewater reuse in agriculture contributes to mitigating the wastewater impact and irrigation pressure on the marshland ecosystem. It is here proposed that a 3.6 ha free-surface flow wetland  could manage the more stringent standard for reuse (15 mg/l) for BOD5 and TSS. A monitoring programme should nevertheless be associated with this kind of project to minimize health risks that may arise as a result of implementation. Despite the absence of studies that deal with wastewater reuse in irrigation projects at the national level (in Iraq), similar studies worldwide provide evidence of reuse possibilities. Furthermore, a performance requirements framework for wastewater reuse in irrigation projects such as the one suggested by Biswas, draws an approach to meet sustainable development indicators and would likely contribute to support and encourage the Marsh Arabs to settle back in their own areas.

The polluted agricultural wastewater, after reaching marine recipients, can cause eutrophication. This problem can be tackled and mitigated by using constructed wetlands as water treatment systems. The fact that constructed wetlands work through long periods of time has led many scientists to evaluate how long they can still treat their influents effectively. The development and growth of vegetation and the accumulation of nutrients on the soils in a wetland are expected to occur. These processes change the wetland efficiency to remove pollutants. In this study, a set of wetlands constructed to treat agricultural wastewater were analyzed in different periods to assess if there is a difference in removal efficiency of nitrogen and phosphorus. This assessment was performed by analyzing the retention rate, k and k20 values, which are variables that quantify the nutrients removal, in different periods of each employed wetland. Some of the observations demonstrated differences when comparing different periods of the wetlands. The nitrogen removal presented better performance in one of the employed wetlands when this was older. Another employed wetland has not shown a clear difference between different periods. In the wetlands with high vegetation densities, the nitrogen removal was more stable over consecutive years. The occurrence of oscillations in nitrogen removal was observed more often in the wetlands with the highest vegetation densities over consecutive years. The phosphorus removal presented no clear differences between different periods. The results suggest that the removal of nitrogen improves after wetland creation due to the growth of vegetation. In addition, they suggest that wetlands with high vegetation densities tend to oscillate the nitrogen removal more or less often according to the density of the vegetation due to the balance between denitrification and decomposition. Further, the results suggest that the removal of phosphorus remains unchanged over longer periods than the periods considered in this study (four to six years) due to the deposition of organic matter on the soils.

Eight agricultural catchments in south Sweden were investigated for factors that may affect phosphorus (P) load and retention in the downstream situated wetlands (WL). P load is known to affect retention, and is determined by hydrological and geographical catchment characteristics. The wetlands were small (0.02-0.88%) in relation to their catchments (CA) and varied in design. Net sedimentation and P retention was determined with sedimentation plates during one year. The variables that best explained differences in particles and TP retention were the hydraulic load (q), TP load and the wetland length to width ratio. Contrary to expectations there was no correlation between factors that could be associated with erosion (i.e. slope and soil clay content) and retention of neither particles nor TP. Generally, the highest amounts of settled particles and P were found close to the wetland inlets, but soil disturbance (i.e. tillage) and high q increased the settling distance. It was likely that the smallest clay particles were too unaggregated to settle within these wetlands. Factors not included, such as wetland vegetation and bioturbation may have a large impact on P retention and this should be further investigated. The study also points to the difficulties in scaling down geological and P loss data from a regional to a local scale, as there can be large local deviations from the regional standard values. An easy method for identification of local “hotspots” for P losses should be of value for planning the location of future wetlands.

In recent years, many construct wetlands in Taiwan have been built for the purposes of wastewater treatment, river water purification, and ecology conservation. To evaluate the effectiveness of constructed wetlands on water purification, frequent water quality monitoring is needed. In this study, the multivariate statistical analysis was applied to evaluate the contaminant removal efficiency in a constructed wetland, and the time series method was then used to predict the trend of the indicative pollutant concentration in the wetland. Multivariate statistical analysis simplifies the original data into representative factors, or hive off the similarity between data to cluster, and then identify clustering outcomes. In this study, an artificial wetlands at the site around an old bridge locates at the Kaoping River Basin was used as the study site. The statistical software SPSS 12.0 was used to perform the multivariate statistical analysis to evaluate water quality characteristics of its. Results from this study show that the removal efficiency for the total coliforms (TC) of System A and B was 98%, 55% for biochemical oxygen demand (BOD), 53% for chemical Oxygen demand (COD), 55% for ammonia nitrogen (NH3-N), and 39% for total nitrogen (TN). Moreover, suspended solids (SS) couldn¡¦t be removed in both A and B systems. The box-and-whisker plot indicates that the water quality of inflow was unstable and variable; however, outflow was turning stable with its flow direction. The major pollutant indicators, except SS, were all in a decreasing tendency. The paired t-test shows p value of each item were lower than 0.05, except total phosphorus (TP) in System A, nitrate nitrogen (NO3-N) and Chlorophyll a (Chl-a) in System B. The correlation parameters from TN, nitrogen oxides (NOx), NO3-N and nitrite nitrogen (NO2-N) and so on were all higher than 0.7. The factor analysis of SPSS shows that 17 water-quality items of the study site could obtain four to six principal components, including nitrate nutrition factor, phosphorus nutrition factor, eutrophication factor, organic factor, and environmental background factor, the major influencing components are nutrition factor and eutrophication factor. The ponds of the study site were classified into two or three clusters depend on in-and-out flow location. This study attempted to establish a forecasting model of wetland pollutants concentration through the time series (ARIMA), results show that the outcome of the B7 pond was better than others. Results indicate that the ARIMA model can be used to simulate the trend of treatment efficiency using the wetland system. Experience and results obtained from this study would provide solutions for water quality control.

In Taiwan, more than 20% of the major rivers are mildly to heavily pollute by domestic, industrial, and agricultural wastewaters due to the low hook-up rate of public underground sewerage systems in rural areas. Thus, constructed or engineered wetlands have been adopted as the major alternatives to cleanup polluted rivers. Constructed wetlands are also applied as the tertiary wastewater treatment systems to polish the secondary wastewater effluents to meet water reuse standards with lower operational costs. The studied Kaoping River Rail Bridge Constructed Wetland (KRRBCW) is the largest constructed wetland in Taiwan. It is a multi-function wetland and is used for polluted creek water purification and secondary wastewater polishment before they discharge into the Kaoping River. Although constructed wetlands are feasible for contaminated water treatment, wetland sediments are usually the sinks of organics and metals. In this study, water, sediment and macrophytes samples were collected from the major wetland basins in KRRBCW. The quarterly investigation (from 2007 to 2009) results show that more than 97% of total coliforms (TC), 55% of biochemical oxygen demand (BOD), and 30% of nutrients [e.g., total nitrogen (TN), total phosphorus (TP)] were removed via the constructed wetland system. However, results from the sediment analyses show that wetland sediments contained high concentrations of metals (e.g., Cu, Fe, Zn, Cr, and Mn), organic contents (sediment oxygen demand = 1.7 to 7.6 g O2/m2-d), and nutrients (up to 18.7 g/kg of TN and 1.22 g/kg of TP). Thus, sediments should be excavated periodically to prevent the release the pollutants into the wetland system and causing the deterioration of wetland water quality. Results of polymerase chain reaction (PCR), denaturing gradient gel electrophoresis (DGGE), and nucleotide sequence analysis reveal that an increase in microbial diversities in the wetland systems was observed. Results from the DGGE analysis indicate that all sediment samples contained significant amounts of microbial ribospecies, which might contribute to the carbon degradation and nitrogen removal. Gradually disappearing of E. coli was also observed along the flow courses through the natural attenuation mechanisms. The factor analysis of SPSS 12.0 shows that 17 water-quality items of the study site could obtain four to six principal components, including nitrate factor, phosphorus factor, eutrophication factor, organic factor, and environmental background factor, the major influencing components are nutrition factor and eutrophication factor. The ponds of the study site were classified into two or three clusters depend on in-and-out flow location. This study attempted to establish a forecasting model of wetland pollutants concentration through the time series (ARIMA), results show that the outcome of the B7 pond was better than others. Results indicate that the ARIMA model can be used to simulate the trend of treatment efficiency using the wetland system. Experience and results obtained from this study would provide solutions for water quality control. Thus, the wetland system has a significant effect on water quality improvement and is capable of removing most of the pollutants from the local drainage system before they are discharged into the downgradient water body. Other accomplishments of this constructed wetland system include the following: providing more green areas along the riversides, offering more water assessable eco-ponds and eco-gardens for public, and rORPabilitating the natural ecosystem. The Kaoping River Rail Bridge Constructed Wetland has become one of the most successful multi-function constructed wetlands in Taiwan. The experience obtained from this study will be helpful in designing similar natural treatment systems for river water quality improvement and wastewater treatment.