Phytoremediation – Aeration System for Treatment of Urban Wastewater

Research Article

Austin Chem Eng. 2017; 4(1): 1047.

Phytoremediation – Aeration System for Treatment of Urban Wastewater

Tripathi DM¹ and Tripathi S²*

¹Department of Microbiology, Bundelkhand University, Jhansi, India

²Institute of Environment and Development Studies, Bundelkhand University, Jhansi, India

*Corresponding author: Smriti Tripathi, Institute of Environment and Development Studies, Bundelkhand University, Jhansi, India

Received: December 21, 2016; Accepted: February 01, 2017; Published: February 03, 2017


The present work was aimed to study the efficiency of Phytoremediation including aeration in treatment of secondary effluent. In the experiment, aquatic plants (Eichhornia crassipes and Lemna minor) were used individually and in combination at 0.0 – 1.6 Lmin-1 aeration for 0 – 120 hrs. In this context, the best results were obtained when the action of Eichhornia crassipes and Lemna minor, was combined with that of 0.4Lmin-1 aeration. Result exhibits promising efficiency towards the removal of BOD (85.49%), COD (85.71%), TKN (80.32%) and TP (80.92%), including heavy metals Fe (73.9%), Cr (66.8%), Cd (75.3%), Cu (73.5%), Zn (79.2%), Pb (76.9%) and Ni (74.9%). Statistical analysis showed significant reduction (p<0.001) in heavy metal content from secondary effluent after treatment. This technique is highly recommendable for tropical wastewater where sewage is mixed with industrial effluents.

Keywords: Aquatic macrophytes; Aeration; Phytoremediation; Heavy metal; Secondary effluent


The anthropogenic activities exploit water resources to fulfill their daily need and create large amounts of wastewater, which have resulted in water pollution [1]. Heavy metals are among the most dangerous substances in the environment, because of their high level of durability and biomagnifications process [2]. Although many metals are essential but all metals are toxic at higher concentrations, cause undesirable effects and severe problems even at very low concentrations [3-5]. It also creates oxidative stress by formation of free radicals by replacing essential metals in pigments or disruption in enzymatic activities [6,7]. Due to discharge of heavy metals from wastewater from industrial, municipal and domestic origin the environment has suffered manifold detrimental effects [1,8]. During the last two decades, reuse of treated has expanded, helping to relieve water scarcity. So that, the demand for storm water treatment to prevent the anthropogenic release of heavy metals into local water bodies, is increasing rapidly [9].

Phytoremediation is a novel bioremediation technology in which plants are utilized to remove or degrade complex environmental pollutants [9]. They perform better purification due to direct contact with contaminated water. Eichhornia crassipes (Water hyacinth) and Lemna minor (duckweed) are hyper accumulator, fast growing and floating plants with a well-developed fibrous root system. It also adapts easily to various aquatic conditions and plays an important role in accumulating metals from water [10-12].

A few studies [7,13,14] have been done on the evaluation of effectiveness of aquatic floating plants, when combined with aeration. In activated sludge system aeration is a key process in wastewater treatment. Its principle role is to supply oxygen, needed for all aerobic treatment processes and to enhance the Dissolve Oxygen (DO) in treated wastewater [15]. Aeration is the dominant source of kinetic energy in an aeration tank [16]. This is one order of magnitude more than suitable mixing devices transfer into the water and several orders of magnitude more than the kinetic energy of the inflowing water or the hydraulic head loss. It also enhances the treatment capacity, facilitates operation at higher organic loading and helps to reduce the required area.

In the present study, the efficiency of the aquatic plants to produce water of higher quality from secondary effluent was investigated, under laboratory conditions. The highest possible treatment efficiency which is attainable in the presence of aquatic plants individually and in mixed culture was explored. This is done in conjunction with local standards levels, which can be reached in a system comprising aquatic plants supplemented with aeration, and the retention time required to this end.

Materials and Methods

Study area and sample collection

Present study was conducted in Varanasi city (82° 15’E to 83° 30’E and 24° 35’N to 25° 30’N). Samples were collected from Bhagwanpur Sewage Treatment Plant which utilizes conventional Activated Sludge Process including trickling filter for the treatment of wastewater.

Samples were collected in plastic containers from effluent channel and transferred to the laboratory, preserved and stored for further analytical determinations and treatment. Methods of preservation include cooling, pH control, and chemical addition. The length of time that a constituent in wastewater will remain stable is related to the character of the constituent and the preservation method used [17].

Experimental design

Phytoremediation with aeration of secondary treated wastewater: The aquatic macrophyte E. crassipes L. and L. minor L. were collected from the Agro farm pond of the Banaras Hindu University, Varanasi, India. The selected macrophytes were cultured individually and in combination with 100% coverage of the total surface area of the 150 L capacity of glass aquariums (0.39 m×0.59 m floor area per container) filled with 95 L of secondary effluent. An aerator was placed on the top of aquarium to maintain the air flow (0, 0.2, 0.4, 0.8 and 1.6 Lmin-1) through porous diffusers positioned into bottom of the aquarium (Figure 1). Control experimental sets contained secondary effluent with plants but no aeration. Five replicates of each experimental set containing macrophytes and control were prepared, i.e., total 30 sets.