Plant Responses to Sewage Pollution

Sewage is the term used for waste water that often contains faeces, urine and laundry waste. The volume of sewage in the world is increasing in leaps and bounds together with the increasing population of the world. So, sewage pollution has become a major problem throughout the world. But the situation is particularly acute in developing countries due to exponential growth of population, urbanization and lack of technical development in these countries. It is important to highlight that although Antarctica has no native human population, yet, unprocessed sewage effluents from various research stations have been reported to cause negative effects on local wildlife of terrestrial and aquatic habitats. Sewage sludge contains excess of nutrients (nitrates, phosphates, organic matter) and heavy metals, which cause eutrophication in water bodies with subsequent increase in algal biomass, primary production and decrease in dissolved oxygen. The over-populating algae and bacteria use up most of the dissolved oxygen of water, making it difficult for other aquatic organisms to live. There are positive as well as negative responses of plants to the sewage effluents. Research shows that low and moderate concentration of sewage irrigation causes stimulated seed germination and seedling growth together with an increase in pigments synthesis, carbohydrates and nucleic acids synthesis. On the contrary, studies reveal that high dose of heavy metal concentration for plants via sewage irrigation/sewage sludge-amended soil caused inauspicious alterations in physiological and biochemical characteristics of plants like a decline in biomass and yield. Furthermore, continuous sewage irrigation in cropland leads to uninterrupted supply of minerals and nutrients resulting in adverse effects on yield quality and biomass due to oxidative damage and risks of plants to counteract stress factors. The plant either becomes toxic to its consumer or it dies from the mineral toxicity. Many plant species provide remedies to the sewage pollution by phytoremediation and this is a cost-effective method for sewage treatment.