Influence of natural plant extracts in reducing soil and water contaminants

Abstract

Water is a fundamental and necessary resource for the life of all living things. In recent times, the sources of pure water have become very limited due to various pollution means which arise from the different industrial advancements. Water pollution has significant adverse effects on the environment and humans. Moringa oleifera (MO) is a multipurpose tropical tree and is currently cultivated in many developing countries, and its seeds contain water-soluble, positively charged proteins that act as an effective coagulant for wastewater treatment. The powdered seed of the MO has coagulating properties that have been used for various aspects of water treatment such as turbidity, alkalinity, total dissolved solids, hardness, and removal of toxic metals. A pot experiment was carried out on lettuce (Lactuca sativa) for the 2016 growing season to study the effect of different water sources, i.e., well water (WW), drain water (DW), sewage water (SW), and groundwater (GW), with or without moringa seed extract (MSE) on reducing water and soils contaminants and its effect on plant growth and heavy metals uptake. Results showed that the lowest values of SSP, SAR, SCAR, RSC, RSBC, PI, PS, KR, and MAR were observed in DW followed by GW, SW, and WW after treated with MSE. The classification of water, i.e., DW, SW, and GW, indicates that all water sources have waters of high salinity-low sodicity before treatment with MSE (C3S1) and moderately low sodicity (C2S1) after treatment with MSE. MSE coagulant has better coagulation capability to reduce water turbidity, NO3–N, BOD, COD, DO, and heavy metals compared with untreated water. Application of MSE to different water sources increased fresh and dry weight and N, P, and K uptake of lettuce plants compared to the untreated waters. Addition of MSE to different water sources gave a significant decrease in Pb, Cd, Ni, Fe, Cu, Zn, and Mn uptake of lettuce plants compared to untreated water. These decreases represent 33, 34, 6, 11, 24, 12, and 25%, respectively, for WW; 7, 37, 23, 12, 14, 19, and 15, respectively, for DW; 38, 45, 33, 13, 32, 34 and 27, respectively, for SW; and 36, 34, 31, 22, 23, 39, and 23%, respectively, for GW. The soil irrigated with different water sources after treatment with MSE gave a significant decrease in the accumulation of Pb, Cd, Ni, Fe, Cu, Zn, and Mn compared to the soil irrigated with different water sources before treatment with MSE. These decreases represent 33, 57, 25, 18, 14, 29, and 21%, respectively, for WW; 41, 58, 36, 14, 24, 38, and 50, respectively for DW; 44, 67, 32, 27, 26, 49, and 30, respectively, for SW; and 35, 50, 28, 15, 18, 53, and 54%, respectively, for GW. Overall, MSE was enough to improve water quality and remove heavy metals from different water sources, lettuce plants, and soil under study. This preliminary laboratory result confirms the great potential of MSE in wastewater treatment applications.