Simultaneous Removal of Salinity and Organic Loading Rate using Phytoremediation

Introduction
Water scarcity has led to the search for alternative water resources. One solution is the recycling of wastewater for irrigation. Wastewater treatment is often based on biological systems such as activated sludge or other engineered units in urban areas. In rural areas, low-cost, environmentally-friendly alternative treatments such as constructed wetlands (CW), are more common. CWs are man-made planted systems that utilize natural processes to improve water quality for human benefit. Salinity in treated wastewater is often increased, especially in arid and semi-arid areas.
Phytoremediation is the use of plants to remove or control of soil and water pollution. Soluble salts, heavy metals, oil and oil derivatives and radioactive substances are pollutants that have been removed using phytoremediation from different environments. In the past two decades, the use of phytoremediation was thrived in the treatment of urban and industrial wastewater and also the treatment of contaminated shallow soil. The sun is the main supplier of energy and is a clean source of energy in terms of creating secondary materials arising from the treatment. Plants use three organs, root, stem and leaves to absorb various pollutants from soil or water. By transferring the pollutant to its tissues, the plant can collect the pollutants from artificial pond cumulatively.
The purpose of this study was to compare the performance of two plants in simultaneous removal of organic matter and salinity of wastewater. In order to have a close estimation of the saline wastewater characteristics, both saline and organic matters were used. A comparison was also done on morphological characteristics of two plants affected by salinity tensions and organic matter in continuing. The results of this study can help the researchers to treat saline wastewater biologically and economically, lateral goals such as creating beauty, producing feed for livestock and also preventing soil erosion.

Materials and methods
Setting up sector includes: the preparation of the mature plant, making the laboratory pilot, preparing artificial wastewater, determining the different concentrations of wastewater, determine the number of plants in each tank, transfer plant to pilot and ultimately add wastewater to the reactor. In order to ensure the effectiveness and safety of plants, rooted plants with a life of at least two months were needed. Therefore, by referring to the vetiver farm belonging to the Iranian Association of promotion and development of Vetiver plant in Tankabon, the required plant was prepared. Swamp palm was provided from the center of Oxus houseplants and transferred to the laboratory. Pilot has 17 batch reactors with a volume of 1.7 liters and was made of Plexiglas according to Figure 1. The aim of this pilot is to create the proper context for simulation of artificial wetlands, existing multiple tanks in order to apply different levels of salinity and different amounts of organic matter to each plant and also compare the amount of removal in tanks containing plant against the control tanks. The pilot was set on the basis of permanent flooding. In this way the platform holder was used that usually kept a plant and directly floated on the reinforced solution. An air pump which has also pumped air into air rocks and created tiny air bubbles in solution, take the required oxygen to plant root. Aeration in addition to supply required root oxygen, also provided mixing in the solution. To measure the parameters, the spectrophotometer system Hach model DR 4000, digital scales PJ300 model manufactured by Mettler by precision of 0.001 hot, EC meter Martini model of MI 805 was used. Stem diameter measurement was done with Vernier caliper with precision of 0.01 cm and measuring leaf area with measuring system of leaf area DeltaT area meter mk2. ATF was used to dry the leaf. In order to make the electrical conductivity in the solution, NaCl was used and to meet required COD of the starch, ultrapure Merck Company used and to prepare solutions, distilled water twice distilled used. Plants were fed with liquid fertilizer Pokon made in Holland. Experiment was done with three replications.


Figure 1. Used pilot in research a) air pump b) reactors with plant c) control reactor

Five wastewaters with different amounts of electrical conductivity and organic matter were produced artificially in the laboratory. Their characteristics are shown in Table 1. Both swamp palm and Vetiver plant in addition to treatment with 5 mentioned wastewaters were irrigated with distilled water as the control. 5 of the reactors without plant was irrigated with mentioned wastewater to be investigate the effect of aeration in reducing the amount of electrical conductivity and COD parameters. In every reactor, the amount of 5 mL liquid fertilizer to provide nutrients and maintain the ratio of NPK at 5: 7: 7 required of plant was added. As long as fertilizing was enough for a period of two months of plant growth. This amount was selected based on the company of making fertilizer. Table 2 provides the reactor arrangement and placement of the plant and control reactors.

Table 1. Amount of salinity and COD in different solutions
Electrical conductivity COD (mg/L) Number


Table 2. Ordering reactors and wastewater and each reactor plant


To investigate the obtained results of removing organic matter and salinity, experiments were done at 5 reactors containing Vetiver plant and control (without plant) during four periods, respectively, 10, 15, 15 and 20 days with the specifications listed in reactors containing wastewater in Table 1.

Discussion & Conclusion
The obtained results of this research in laboratory scale showed that using phytoremediation method in artificial wetland, in different levels of salinity and organic matter, on average, for every single plant and vetiver 17%, and per unit of swamp palm plant have had 15% salinity reduction and wastewater in following. Other results are as follows:
The process of reducing the amount of electrical conductivity in both species reduced with increasing salinity levels. The highest amount of salt intake by plant of swamp palm in the electrical conductivity was observed 2500 micro Siemens per centimeter and about 30% and about 53% for Vetiver.
The process of reducing organic matter in both species reduced with increase in salinity level with the highest efficiency of COD reduction by plant of swamp palm in the electrical conductivity was observed 0 and organic matter mg / L 300 about 50% and for Vetiver plant about 58%.

Comarison of COD and Electrical Conductivity Removal

Based on the measurement results and the importance of plants, the highest level of leaf area, dry weight and diameter of stem was obtained in vetiver plant and the highest root velum in swamp palm plant. All of these characteristics according to salinity tolerance by the plant, since the transfer to pilot have increased the toxicity and wilting in the mentioned plants and since then has remained static or due to loss of plant and destruction of associated tissue was reduced. Chlorosis in Vetiver plants shows the accumulation of salt in the root that indicates the process of root phytoremediation in this plant. Creating Toxic effects on palm leaves and also the tiller of the plant in salinity before the drought threshold acts as a control on dilution mechanism in phytoremediation of swamp palm. This mechanism was observed in Vetiver due to observing green tillers.
By changing the rinsing characteristics of plant and also destroying the balance of plant enzymes, the electrical conductivity of solution causes reduction in the amount of water taking, drought of plant and results in the lack of transfer of pollutants from the flooding environment into the tissues of plant. Finally, Vetiver plant was diagnosed in comparison to swamp palm for phytoremediation of saline wastewater with appropriate organic matter.