Sewage Sludge: An Important Biological Resource for Sustainable Agriculture and Its Environmental Implications

TLDR

Sewage sludge, a nutrient‑rich by‑product of wastewater treatment, is increasingly used as an organic fertilizer to offset high mineral fertilizer costs, though its contamination with pathogens and heavy metals poses environmental risks. This review examines the sustainability and economic benefits of applying sewage sludge to agricultural soils, addressing its nutrient‑cycling potential and disposal advantages. The review discusses using sewage sludge as a fertilizer and soil conditioner, highlighting its high organic matter and macro‑ and micro‑nutrient content for crops and pasture.

Abstract

Intensive farming generally needs large addition of organic matter to maintain fertility and enhance crop yields. Sewage sludge/biosolids are by-products of municipal and industrial wastewater treatment and a rich source of organic nutrients. Sewage sludge having high content of organic matter, macro- and micro-nutrients, can be used as fertilizer/soil conditioner for food, vegetable crop, horticultural plants and pasture, which in most cases can be beneficially recycled. In the past sewage sludge was regarded as a waste product due to expected high level of contaminants such as pathogens, pollutants and synthetic materials discharged in sewer from homes and industries, which were often incinerated, dumped in occasion or land fill. As a result of rapidly increasing population, urbanization and industrialization, wastewater production and sewage sludge generation have increased manifold. Due to high cost of mineral fertilizers and escalating trends in their prices, there is an increasing trend of using sewage sludge in agriculture, especially under intensive cropping in arid and semi arid regions of the country. Therefore, application of sewage sludge to agricultural soils may be sustainable and economical due to nutrient cycling and disposal of sewage sludge. However, there may be a risk in use of sewage sludge due to potentially harmful contents present in the sludge such as heavy metals and pathogens. This paper, therefore, presents a review on various aspects of sewage sludge used in agriculture.