Tereza Březinová

The use of constructed wetlands for removal of pesticides from agricultural runoff and drainage: A review

Pesticides are used in modern agriculture to increase crop yields, but they may pose a serious threat to aquatic ecosystems. Pesticides may enter water bodies through diffuse and point sources, but diffuse sources are probably the most important. Among diffuse pollution, surface runoff and erosion, leaching and drainage represent the major pathways. The most commonly used mitigation techniques to prevent pesticide input into water bodies include edge-of-field and riparian buffer strips, vegetated ditches and constructed wetlands. The first attempts to use wetland macrophytes for pesticide removal were carried out as early as the 1970s, but only in the last decade have constructed wetlands for pesticide mitigation become widespread. The paper summarizes 47 studies in which removal of 87 pesticides was monitored. The survey revealed that constructed wetlands with free water surface are the most commonly used type. Also, it has been identified that removal of pesticides is highly variable. The results of the survey revealed that the highest pesticide removal was achieved for pesticides of the organochlorine, strobilurin/strobin, organosphosphate and pyrethroid groups while the lowest removals were observed for pesticides of the triazinone, aryloxyalkanoic acid and urea groups. The removal of pesticides generally increases with increasing value of KOC but the relationship is not strong.

Occurrence, removal and environmental risk assessment of pharmaceuticals and personal care products in rural wastewater treatment wetlands

Rural communities in central and eastern Europe usually use constructed wetlands (CWs) to treat domestic wastewater. Effluents from these systems are regularly discharged to receiving water, resulting in a potential transfer of pharmaceuticals and personal care products (PPCPs) from sewage to the aquatic environment. In this study, the seasonal occurrence, removal and risk assessment of 32 multi-class PPCPs were investigated in three CWs from the village of south Bohemia, Czech Republic. Among the PPCPs considered, 25 compounds were detected in sewage influent, and ibuprofen, caffeine and paracetamol were the most commonly detected PPCPs. The removal efficiencies of PPCPs in the rural CWs exhibited large variability with 11-100% for anti-inflammatories, 37-99% for β-blockers and 18-95% for diuretics. The statistical results revealed significant correlations between removal efficiencies of six PPCPs and conventional water quality parameters. The ecotoxicological assessment study revealed that most of the PPCPs (except ibuprofen) in the effluent yielded low aquatic risk. This study suggested that constructed wetlands could be effective for removing PPCPs and reducing environmental risk of PPCPs discharged from rural communities into surface water systems.

Occurrence and removal of estrogens, progesterone and testosterone in three constructed wetlands treating municipal sewage in the Czech Republic.

Estrogenic hormones, progesterone and testosterone are endocrine-disrupting chemicals and their presence in aquatic environments represents a potentially adverse environmental and public health impact. There is a considerable amount of information about removal of estrogens, progesterone and testosterone in conventional wastewater treatment plants, namely activated sludge systems. However, the information about removal of these compounds in constructed wetlands is very limited. Three constructed wetlands with horizontal subsurface flow in the Czech Republic have been selected to evaluate removal of estrogens (estrone, estriol, 17β-estradiol, 17α-ethinylestradiol), testosterone and progesterone. Monitored constructed wetlands for 100, 150 and 200 PE have been in operation for more than 10 years and all systems exhibit very high treatment efficiency for organics and suspended solids. The results indicate that removal of all estrogens, progesterone and testosterone was high and only estrone was found in the outflow from one constructed wetland in concentrations above the limit of quantification 1 ng l(-1). The limits of quantification for other estrogens, i.e., 10 ng l(-1) for estriol, 1 ng l(-1) for 17β-estradiol and 2 ng l(-1) for 17α-ethinylestradiol were not exceeded in the outflow of all monitored constructed wetlands. Also, for progesterone and testosterone, all outflow concentrations were below the LOQ of 0.5 ng l(-1). The results indicated that constructed wetlands with horizontal subsurface flow are a promising technology for elimination of estrogens, progesterone and testosterone from municipal sewage but more information is needed to confirm this finding.

Treatment of a small stream impacted by agricultural drainage in a semi-constructed wetland

During the period 2014-2016, removal of nutrients, organics and suspended solids from a small rural stream impacted by agricultural drainage in a natural and semi-constructed wetlands was evaluated. In 2014, the wetland was irregularly flooded during high flows in the stream, in 2015, the stream bed was cleaned and as a result the water level dropped down by about 0.5 m, thus no flooding occurred. In 2016, the stream was blocked and water was permanently diverted into a wetland dominated by Phalaris arundinacea, Carex nigra and Scirpus sylvaticus. The results clearly revealed a positive role of permanent flooding resulting in the highest removal of all monitored parameters, i.e. nitrogen (38%), phosphorus (40%), BOD5 (42%) and suspended solids (67%). The permanent flooding increased aboveground biomass of P. arundinacea and C. nigra while S. sylvaticus was eliminated by permanent flooding. The repeated harvest yielded higher aboveground biomass for P. australis and S. sylvaticus, while for C. nigra one harvest provided more biomass. In 2016, the removal expressed as the loading averaged 1102 kg TN ha-1 yr-1 and 894 kg NO3-N ha-1 yr-1 and the plant uptake was responsible for removal of 36.1% TN. The average removal of total phosphorus amounted to 164 kg P ha-1 yr-1 with plant uptake being responsible for 18.7%. Average removal of BOD5, COD and TSS amounted to 1108, 5953 and 9220 kg ha-1 yr-1, respectively. While the removal of BOD5 and COD increased exponentially with increasing water temperature, removal of TSS was not affected by water temperature. The results proved that slightly modified natural wetlands with negligible investment costs can be as effective as fully constructed wetlands to treat agricultural drainage.

Distribution of Phosphorus and Nitrogen in Phragmites australis Aboveground Biomass

The objective of this study was to evaluate nitrogen and phosphorus compartmentalization in the aboveground biomass of Phragmites australis and its seasonality. The study was carried out at four sites in the littoral zones of two fishponds near Prague, Czech Republic. The aboveground biomass was harvested in early July and late August and the biomass was divided into thirds and stems and leaves. Besides dry weight of the biomass, concentrations of nitrogen and phosphorus were determined. The results revealed that the proportion of biomass formed by stems increases during the season. The concentrations of both nitrogen and phosphorus were higher in July and higher in leaves. Phosphorus standing stock is higher in stems then leaves while nitrogen standing stock is higher in leaves then in stems. The highest N and P standing stocks were found in upper leaves both in July and August.

Decomposition of Phragmites australis in Relation to Depth of Flooding

Decomposition of Phragmites australis in relation to water depth was studied in the littoral reed stands of two fishponds near Prague during 2014. In both fishponds, three sites were selected along the water depth gradient – deep and shallow water in the littoral zone and above the water. The sites above the water were located in the area which never got inundated. P. australis aboveground biomass was collected at all sites in both fishponds in October 2013 and the collected biomass was divided into leaves, lower stems and upper stems (stem was divided in two parts of equal length). The litter bags with mesh size of 1 mm were filled with about 3 g of each plant part and exposed at all locations in six replications in December 2013. The litterbags were taken out in regular 3-month intervals, the biomass was divided into particular plant parts, carefully cleaned from the sediment, dried at 60 °C to a constant weight and weighed. It has been found that stems and leaves of Phragmites australis decompose at various rates in the order of leaves > upper stems > lower stems. The difference in decomposition rates for upper and lower stems and leaves was significant. Average time necessary for 50 % dry mass loss was 708 days for lower stems, 411 days for upper stems and 233 days for leaves. The decomposition of P. australis proceeded slower above the water than in the littoral zone under submerged conditions. There was no significant difference between decomposition rates in deep and shallow water. The decomposition rate above the water was slower by 20 %, 39 % and 45 % for lower stems, upper stems and leaves, respectively.