Wastewater treatment has been a challenge throughout the years due to varying influent characteristics and stringent effluent regulations. In response to this dilemma, a reliable, cost-effective and high-efficiency sequencing batch reactor (SBR) technology has been recently developed. SBRs are variations of the activated sludge process that operates on a fill-and-draw basis. It combines both aerobic-anaerobic phases in one unit and saves up to 25% of the aeration costs concomitant with low sludge production. Consequently, simultaneous nitrogen and phosphorus removal from the wastewater could be achieved by adjusting the actual operating cycle. This review paper discusses the technical description and operational flexibility of SBR for the treatment of wide range of effluent under different operational conditions, together with its modifications that could increase the effectiveness of SBR systems in the future.

Constructed wetlands (CW) are well known for removal of organics, suspended solids, nutrients, and bacteria. However, the information on removal of heavy metals and their sequestration in plants especially, the ornamental plants is very limited. In this experimental study, efficiency of horizontal subsurface‐flow constructed wetland (HSCW) planted with an ornamental species Polianthus tuberosa L. was evaluated for heavy metal sequestration in the phytomass. The plants were harvested during the peak standing crop in early September, divided into leaves, inflorescence, roots, and rhizomes, and analyzed for six trace elements (Cu, Zn, Ni, Al, Pb, and Fe). Metal concentrations decreased in the order of roots > rhizomes > leaves > inflorescence. The highest concentration in aboveground biomass were recorded for Al (3.66 mg kg−1) and Fe (1.35 mg kg−1), while the lowest concentration was recorded for Pb (0.06 mg kg−1). Belowground biomass also followed the same decreasing trend, the highest concentrations being recorded for Al (6.28 mg kg−1) with 5.78 mg kg−1 and 6.09 mg kg−1 concentration in rhizomes and roots, respectively. The lowest concentration in belowground biomass was recorded for Ni (0.28 mg kg−1) and Pb (0.17 mg kg−1). The belowground/aboveground concentration ratio ranged between 1.19 and 5.13 with an average value of 2.50. Due to average belowground/aboveground biomass ratio < 1, the belowground/aboveground standing stock ratios for all the metals were > 1 except Fe (0.79). The maximum values for bioconcentration factor (BCF) were found for Al and Zn 81.5 and 16.3, respectively. Biological accumulation factor (BAF) and transfer factor (TF) values were > 1 and <1, respectively for most of the heavy metals, which suggests their immobilization in the roots/rhizosphere and therefore, the species can be best suited for phytostabilization. The results of this study therefore provide the comprehensive information on sequestration of Cu, Zn, Ni, Al, Pb, and Fe in vegetation during domestic wastewater treatment in CW with horizontal subsurface flow. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 125–132, 2016

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Vegetation filter is an emerging wastewater treatment option in which phytoremediation strategies are employed for municipal applications. Short rotation woody crops combine both treatment and reuse of effluent and operate on ‘zero discharge' concept. This multifunctional system has become a viable alternative solution for wastewater treatment as well as biomass production by utilizing nutrient rich wastewater as cost efficient fertilizer. Fast growing species like Salix, Eucalyptus, and Populus with high water and nutrient requirements, highly selective heavy metal uptake and high evapotranspiration rate are generally preferred as vegetation filters for wastewater treatment. However, site-specific factors such as wastewater composition, climate, soil type, permeability, species or clonal characteristics must be taken into account when considering irrigation with municipal wastewater. This chapter discussses the prospects for vegetation filters to remediate contaminated water and soil and also facilitate recycling of valuable resources in society.