Biochemical responses of some aquatic plants as indicators for the treatment of inorganic nitrogen compounds in wastewater (Case study: Domestic water treatment plant in Babil Governorate, Iraq)

The current study was conducted to investigate the biochemical response of two plant species including Lemna minor and Ceratophyllum demersum as indicators for the treatment and reducing the concentrations of dissolved inorganic nitrogen compounds in wastewater collected from a domestic water treatment plant in Al-Maamera area in Babil Governorate, Iraq. The experiment included the cultivation of aquatic plants in 20-liter plastic basins, which contain domestic water collected from the sedimentation basins at the station after completing the physical and chemical treatment. Some physical and chemical tests were conducted and the concentrations of some compounds of dissolved inorganic nitrogen were measured by taking the water samples every three days for a period of twenty four days. The current study showed that the pH values were raised to the basal direction when wastewater treated with C. demersum, while the values fluctuated when using L. minor with treatment between low and slight increase at other times. On the other side, the efficiency of the aquatic plants used in current study in decreasing the values of both electrical conductivity and total dissolved solids was weak and was limited to the first days of treatment. The results recorded an increased oxygen concentration when wastewater treated with C. demersum compared to the control which recorded higher concentrations than L. minor. The study showed also that the L. minor and C. demersum have very high efficiency in reducing the inorganic nitrogen compounds. So that, in the case of L. minor, the highest removal rate of nitrite, nitrate and ammonia were 99.36%, 88.04% and   81.25 %, respectively, while in the case of C. demersum, the related rates were 99.36%, 78.8% and 86.6 % respectively. As for the physiological condition of the plants, the results in the current study showed that the total chlorophyll values in L. minor and C. demersum increased after completing the phytoremediation. The MDA content decreased, while CAT enzyme was not affected   by both plants. The SOD enzyme was not also affected by L. minor, while a rise in this enzyme was recorded by C. demersum.