Analyzing Remediation Potential of Wastewater Through Wetland Plants: A Review Misha Bhatia and Dinesh Goyal Department of Biotechnology, Thapar University, Patiala 147004, Punjab, India; dgoyal@thapar.edu (for correspondence) Published online 00 Month 2013 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ep.11822 Treatment of different wastewater using macrophytes- vegetated constructed wetland reveals its potential in terms of significant reduction in BOD, COD, suspended solids, total solids, total nitrogen, heavy metals along with remediation of xenobiotics, pesticides and polyaromatic hydrocarbons. The rhizosphere of macrophytes such as Phragmites, Typha, Juncus, Spartina and Scirpus serves as an active and dynamic zone for the microbial degradation of organic and sequestra- tion of inorganic pollutant resulting in successful treatment of domestic, textile and other effluents. Up to 2049–6648 mg metal per gram dry weight of plant biomass are found to accumulate in plant parts i.e. shoots and roots. Major metal removal mechanisms are bioaccumulation in plant parts, phy- toextraction and phytostabilization. Different wastewaters treated through this technology are industrial, domestic, dairy, pesticides, PAHs, and xenobiotics containing effluents. Load- ing limits of the wetland, removal efficiency, biomass disposal and variation in seasonal growth are some of the limiting fac- tors which can be overcome by stimulating the plant microbe interaction through designer rhizospheres involving pigmenta- tion, biostimulation and genetic alterations of plant and asso- ciated microbial community. V C 2013 American Institute of Chemical Engineers Environ Prog, 00: 000–000, 2013 Keywords: wastewater, bioaugmentation, designer rhizo- spheres, biostimulation, constructed wetlands INTRODUCTION Comprising over 70% of the Earth’s surface, water is the most precious natural resource that exists on our planet [1]. Most water pollutants are eventually carried by rivers into the large water bodies no longer leaving them clean or pure; pos- ing human health risks. Water is referred to as polluted when it is impaired by anthropogenic contaminants and either does not support a human use (like serving as drinking water) or undergoes a marked shift in its ability to support its constitu- ent biotic communities [2]. For water pollution two general categories exist: direct and indirect. The former include efflu- ent outfalls from factories, refineries, and waste treatment plants etc., that emits fluid of varying quality directly into urban water supplies. The latter includes contaminants that enter the water supply from soil= groundwater systems and from the atmosphere via rain water. Soils and ground waters contain the residue of human agricultural practices (fertilizers, pesticides, etc.) and improperly disposed of industrial wastes [3]. Some major pollutants found in contaminated waters are heavy metals, xenobiotics, nutrients, organic matter and acidi- fying gases such as sulfur dioxide. The discharge of effluent from domestic and industrial sources has detrimental effects on the aquatic ecosystem [4] as this outfall can deposit large amount of organic matter, nutrients and pollutants leading to eutrophication (fertilization of surface water by nutrients that were previously scarce), temporary oxygen deficits and accu- mulation of pollutants into receiving waterways. In the last few decades, researchers have tried to adopt an eco-technological approach to clean up or remediate wastewater using plants. This use of plants termed phytore- mediation (phyto meaning plant and remedium meaning to clean or restore) actually refers to diverse collection of natu- ral or genetically engineered plants for cleaning contami- nated environments [5]. Eventually combining the existing biological and engineering strategies to improve the applic- ability of phytoremediation has come up in the form of con- structed wetlands (CW) using plants termed macrophytes which according to USEPA are aquatic plants, growing in or near water that are emergent, submergent, or floating. Pres- ent review aims to sum up different aspects of constructed wetlands, design, construction and its applications for treat- ing various effluents. Some attempts to improve the model system using novel techniques are also discussed. CONSTRUCTED WETLANDS The Ramsar convention brought wetlands to the attention of the world and proposed the following definition: Wetlands are areas of marsh, fern, peat land or water whether natural or artifi- cial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed 6 m [6]. Constructed wet- lands are complex biological system that mimics natural self- cleansing processes [7] by reducing pollutant level to a dis- chargeable limit. In fact these can be treated as nature’s kidneys. Root morphology and depth are important plant characteristics for phytoremediation. A fibrous root system (found in grasses e.g., Fescue), has numerous fine roots spread throughout the soil and provides maximum contact with the soil due to the high surface area of the roots. A tap root system (such as in alfalfa) is dominated by one larger central root. Root depth directly impacts the depth of soil that can be remediated or depth of ground water that can be influenced, as close contact is needed between the root and the contaminant or water [8]. Some com- mon plants used in wetlands are listed below in Table 1. A universally used plant species is Phragmites [30,31] commonly called reeds, which contribute to wastewater cleaning processes in many different ways: increasing the permeability and porosity of substrate [32], creating micro sites with reducing conditions by releasing oxygen from the roots [33,34] termed as ROL (Radial oxygen loss). Through these oxygenated and oxygen poor micro sites even resistant V C 2013 American Institute of Chemical Engineers Environmental Progress & Sustainable Energy (Vol.00, No.00) DOI 10.1002/ep July 2013 1