4.1 Wetland Systems
Natural wetlands are the areas of transition between terrestrial and aquatic systems
(Fig. 11.6). Previously, depending on plants present, wetlands have been called
swamps, bogs or ecotones, sloughs, and marshes (Fig. 11.6). Wetlands can be
defined as:
An area where the water table is at or near the surface/land that is covered by shallow water
supported predominantly by hydrophytes (water-tolerant plants) and consisting of
undrained hydric soils wet enough for time period to produce anaerobic conditions limiting
the variety of plants growing on them.
Wetland support vegetation and have higher biological activity, act as groundwater recharge and discharge, and stabilize and protect the shores of seas, riverbanks, and lakes from erosive tides, floods, storms, winds, and waves.
4.2 Constructed Wetlands
These are the wetlands that are constructed or engineered to treat wastewater and
improve water quality (Bharagava et al. 2017c). Their wastewater treatment capability and wide range of applications have attracted researches all over the world to
explore this technology to treat domestic and industrial wastewater, agricultural
flows, landfill leachates, etc. In a constructed wetland, the three main compartments,
i.e., substrate (sediment), hydrology, and vegetation, play an important role in the
remediation of toxic metals or other pollutants. The substrate harbors consortia of
detritus microbes, which are responsible for toxicity reduction and transformation,
which may cause the biomineralization. The physical processes in constructed
wetlands through which these metals are removed from contaminated waters include
settling and sedimentation following the adsorption on particulate matter. To some
extent, mats of floating plants serve as sediment traps, while rooted and floating
plants regulate the flow rate of water by providing the resistance. In sediments, the
metals are adsorbed onto the particles by either cation exchange or chemisorptions.
There are two major types of constructed wastewater wetlands shown in
Fig. 11.7:
1. Free water surface wetland (FWS) resembles natural wetlands and encompasses
shallow water flowing over plant media with water depths varying all over
wetland.
2. Vegetated submerged bed wetland (VSB) constitutes of coarse substrate media
like gravel through which water travels. They remove contaminants by different
means but with common mechanisms and basic processes. Figure 11.7 below
depicts the types of constructed wetlands. For treatment in wastewater wetlands,
there are three basic mechanisms: Biological, physical, and chemical. In the
traditional physical method of wastewater treatment, plants in the wetland help
270
M. Rastogi and M. Nandal
Natural wetlands are the areas of transition between terrestrial and aquatic systems
(Fig. 11.6). Previously, depending on plants present, wetlands have been called
swamps, bogs or ecotones, sloughs, and marshes (Fig. 11.6). Wetlands can be
defined as:
An area where the water table is at or near the surface/land that is covered by shallow water
supported predominantly by hydrophytes (water-tolerant plants) and consisting of
undrained hydric soils wet enough for time period to produce anaerobic conditions limiting
the variety of plants growing on them.
Wetland support vegetation and have higher biological activity, act as groundwater recharge and discharge, and stabilize and protect the shores of seas, riverbanks, and lakes from erosive tides, floods, storms, winds, and waves.
4.2 Constructed Wetlands
These are the wetlands that are constructed or engineered to treat wastewater and
improve water quality (Bharagava et al. 2017c). Their wastewater treatment capability and wide range of applications have attracted researches all over the world to
explore this technology to treat domestic and industrial wastewater, agricultural
flows, landfill leachates, etc. In a constructed wetland, the three main compartments,
i.e., substrate (sediment), hydrology, and vegetation, play an important role in the
remediation of toxic metals or other pollutants. The substrate harbors consortia of
detritus microbes, which are responsible for toxicity reduction and transformation,
which may cause the biomineralization. The physical processes in constructed
wetlands through which these metals are removed from contaminated waters include
settling and sedimentation following the adsorption on particulate matter. To some
extent, mats of floating plants serve as sediment traps, while rooted and floating
plants regulate the flow rate of water by providing the resistance. In sediments, the
metals are adsorbed onto the particles by either cation exchange or chemisorptions.
There are two major types of constructed wastewater wetlands shown in
Fig. 11.7:
1. Free water surface wetland (FWS) resembles natural wetlands and encompasses
shallow water flowing over plant media with water depths varying all over
wetland.
2. Vegetated submerged bed wetland (VSB) constitutes of coarse substrate media
like gravel through which water travels. They remove contaminants by different
means but with common mechanisms and basic processes. Figure 11.7 below
depicts the types of constructed wetlands. For treatment in wastewater wetlands,
there are three basic mechanisms: Biological, physical, and chemical. In the
traditional physical method of wastewater treatment, plants in the wetland help
270
M. Rastogi and M. Nandal