Interactions between Plants and Faecal Microorganisms in Urban Stormwater Biofilters: Significance of Plant Debris and Root Exudates

Stormwater is a valuable alternative water resource which can reduce the pressure on existing water resources in urban areas. Biofiltration is a sustainable treatment technology which has shown promising results in removing these microbial pollutants of concern. However, current stormwater biofilters are not optimized for pathogen removal and hence, a wide variance in removal performances is reported in literature. It is often reported that the variable faecal microbial removal in stormwater biofilters is due to the influence of different biofilter design factors and operational condition on microbial retention and survival processes within stormwater biofilters. Efforts have been made to improve filter media for faecal microbial removal, but relatively little is explored on the potential of the biotic processes related to plants and/or soil microorganisms for pathogen removal in stormwater biofilters

Geochemistry of pillow lavas and their clinopyroxene: ophiolitic mélanges of Nain and Ashin, northeastern Isfahan province

The Nain and Ashin ophiolites are located in northeastern Isfahan province, in western Central-East Iranian Microplate. Pillow lavas are one of the most significant Cretaceous rock units. The lower partial melting degree in mantle peridotites of Ashin ophiolite, and the derived melt by melting their clinopyroxene caused a more basic (basalt) and enriched nature for the Ashin pillow lavas, whereas higher partial melting degree and consequently incongruent melting of orthopyroxene and increment of silica in the ascending melt, together with aqueous fluids led to formation of more acidic (andesite – basaltic andesite) and depleted melts (in trace elements) in Nain ophiolite. The REE content of Nain samples have IAT chemical affinity, but the samples from Ashin show MORB characteristics. Based on petrograhic observations, lower Eu/Eu* of clinopyroxene phenocrystals of Ashin, calculated Kd of clinopyroxene together with HREE enrichment in the melt in equilibrium with clinopyroxene (especially in Ashin when compared with Nain), the plagioclase crystallization was primer and higher in comparison with clinopyroxene, especially in Ashin compared with Nain. The melt in equilibrium with clinopyroxene in Ashin was similar to MORB composition, whereas it is similar to IAT in Nain. Thus, despite the proximity of these two ophiolitic series and some field and petrographic similarities, pillow lavas from them are different from each other in both primary melt composition and the processes of differentiation and the tectonic setting

Microbial Communities and Nitrogen Transformation in Constructed Wetlands Treating Stormwater Runoff

Microbial communities play a vital role in nitrogen (N) removal in constructed wetlands (CWs). However, the lack of studies on microbial characteristics of wetland systems designed to treat stormwater demonstrates the importance of comprehensive investigation on microbial response to wetland fluctuations. Moreover, the observed inconsistency in N removal, and detected links between microbial shifts and wetland water level fluctuations is an area of research interest perculiar to stormwater applications. This study surveyed nearly 150 publications to provide a summary and evaluation of N removal efficiency in different types of CWs where microbial communities and their behavior have been correlated to regulating factors. Factors such as flow regime, plants, and physico-chemical properties (e.g., temperature, dissolved oxygen, pH, and nitrogen concentration) were found to significantly influence microbial diversity and composition. Although many studies have analyzed microbial N removal, a majority conducted their studies in bioretention systems. Accordingly, some of the microbial pathways in CWs designed for stormwater treatment have not been investigated. As such, it is suggested that pathways, such as dissimilatory nitrate reduction to ammonium (DNRA) and comammox activity and their changes over dry-wet cycles in stormwater constructed wetlands be investigated. This information could assist engineers to take advantage of the presence of other N transforming communities which could improve microbial diversity within wetland systems. Moreover, it is recommended to track microbial functional genes and their changes over wetland water fluctuation to develop an ecosystem with conditions favorable for microbial pathways with higher N removal potential. In conclusion, the findings of the current literature review reinforce the importance of stormwater runoff treatment and the implementation of new design strategies that are able to enhance microbial activity and diversity leading to a better treatment outcome.</jats:p

Tectonomagmatic settings of Jurassic granitoids in the Sanandaj-Sirjan Zone, Iran: A review

The present paper discusses the geochemical affinities, origin and ages of Jurassic granitoids of the Sanandaj-Sirjan Zone (SaSZ) in the eastern part of the Zagros Thrust Zone. A multidisciplinary, integrated approach was carried out using existing granitoid geochemical data (major, trace, rare earth element and isotopes) and knowledge of the regional geology (geodynamic and metamorphic setting), coupled with geophysical data (magnetic susceptibility) from granitoids in the SaSZ. We re-interpret and re-classify the Jurassic granitoids of this zone into three main genetic groups: S-type, I-type and A-type subduction-related ones. In the central to southern part of the Sanandaj-Sirjan zone (between Hamadan and Sirjan), S-type magmatism appeared between 178 and 160 Ma during the Cimmerian orogeny, due to continental collision. To the north of the Sanandaj-Sirjan zone (between Sanandaj and Ghorveh), I-type and A-type magmatism occurred between 158 and 145 Ma. This heterogenic tectonomagmatic system along the SaSZ suggests a heterogenic subcontinental lithospheric mantle, resulting in two Jurassic tectonomagmatic zones of (1) the Sanandaj-Ghorveh Zone and (2) the Hamadan-Sirjan Zone

Plants that can kill; improving E. coli removal in stormwater treatment systems using Australian plants with antibacterial activity

Sustainable stormwater treatment systems remove pollutants using low energy, low maintenance and low cost solutions. Inactivation due to biotic stressors is one of the processes that govern the removal of faecal microorganisms in these systems. One such stress is the possible production of antimicrobial compounds by plants growing in sustainable stormwater treatment systems, potentially enhancing the removal of faecal pathogens. To this end, this study has investigated the antimicrobial potential of 17 Australian native plant species that are suitable for application in these systems but have not been tested for their antimicrobial activity within their seed exudates, seed extracts and/or seedling extracts. The extracts and exudates were tested using the agar well diffusion method. Nine of the selected plant species inhibited the growth of Escherichia coli. Among of the antibacterial plants, Melaleuca ericifolia, which has been previously applied in stormwater treatment systems, can be a suitable candidate for further study as it demonstrated antibacterial activity within all tested components. This species should be utilised in stormwater treatment facilities due to its effective nitrogen uptake, maintenance of hydraulic conductivity, and due to its potential effectiveness at inactivating microbial pathogens.</p

Retention and survival of E. coli in stormwater biofilters: role of vegetation, rhizosphere microorganisms and antimicrobial filter media

The public health risks associated with pathogens in urban stormwater have been well established, making it necessary to ensure adequate treatment of the stormwater before it is discharged into recreational water bodies or is harvested for reuse. Biofilters, also known as stormwater bioretention systems or raingardens, have shown promising, yet variable, results in reducing indicator bacteria in stormwater. Different biofilter design elements, such as filter media composition and vegetation type, have been found to cause this variable removal performance. Although plants play a key role in the treatment of pollutants, relatively little work has been conducted to understand the importance of interactions between vegetation and the biofilter microbial community on fecal microbial removal. A laboratory-scale biofilter experiment was conducted using Escherichia coli as the test fecal microorganism. Biofilter columns with differing soil media and vegetation types were dosed over a two month span, during which inflow and outflow samples were collected to evaluate system performance. The columns were then decommissioned to collect rhizosphere and bulk soil samples. Root exudates were extracted and used in an E. coli survival study to evaluate their contribution to system performance. The study demonstrated that the antagonistic effects of root exudates/rhizosphere microbes and Cu2+ exchanged zeolite antimicrobial filter media adversely impact the survival of E. coli retained within stormwater biofilters. Furthermore, leaf and flower/seed extracts of L. continentale showed some potential antibacterial activity against E. coli. This work supports the concept that natural processes in biological systems can deliver effective results in the removal of fecal microorganisms, and should be promoted to the extent possible in stormwater green infrastructure.</p