How can sewage treatment improve soil quality?

1 Why soil quality matters

Soil quality is the capacity of soil to perform its functions and support plant growth, biodiversity, and ecosystem services. Soil quality depends on various factors, such as texture, structure, organic matter, nutrient content, pH, salinity, and microbial activity. Healthy soil can improve crop yields, water infiltration, carbon sequestration, and resilience to climate change and erosion. However, soil quality is under threat from human activities, such as intensive farming, deforestation, urbanization, and pollution.

2 How sewage treatment works

The process of sewage treatment involves a series of physical, chemical, and biological processes to remove solids, organic matter, nutrients, and pathogens from wastewater. Preliminary treatment is the first step and uses screens, grinders, and sedimentation tanks to remove large objects, grit, and grease. Primary treatment follows this by using gravity or flotation in clarifiers or settling tanks to separate suspended solids from wastewater. The solids form a sludge that can be further treated or disposed of. Secondary treatment degrades organic matter and nutrients from wastewater using microorganisms in aerobic or anaerobic conditions. The microorganisms can be suspended in activated sludge or attached to fixed media in trickling filters or biofilters. The treated wastewater is then separated from the biomass in secondary clarifiers. Finally, tertiary treatment polishes the wastewater to meet higher standards of quality and safety using advanced methods such as filtration, disinfection, membrane separation, or nutrient removal. The treated wastewater can then be reused for irrigation, industrial, or domestic purposes.

4 How treated wastewater can improve soil quality

Treated wastewater is the liquid effluent that results from sewage treatment, and it can be reused for a variety of purposes depending on its quality and safety. Reusing treated wastewater for irrigation offers several benefits, such as conserving freshwater resources and reducing water stress in arid regions, supplying water and nutrients to crops, leaching salts and toxins from the soil, and increasing soil moisture and organic matter. All of these benefits can improve crop growth, yield, quality, soil structure, infiltration, and aeration.

5 How to use sewage treatment products safely and effectively

Sewage treatment products, such as sewage sludge and treated wastewater, can improve soil quality, but they can also pose risks and challenges. These include the potential for containing pathogens, heavy metals, organic pollutants, and emerging contaminants that can harm human and environmental health, as well as causing odors, pests, and aesthetic problems. Additionally, these products may require additional infrastructure, equipment, and regulations to ensure their proper collection, treatment, storage, transport, and application. To ensure safety when using sewage treatment products for soil improvement, it is important to follow best practices and guidelines. This includes monitoring and controlling the quality and quantity of the product according to its source and end use; applying it according to the soil type, crop type, climatic conditions, and agronomic practices; protecting workers, consumers, and the environment from exposure to pathogens and pollutants; and educating stakeholders on the benefits and risks of using sewage treatment products.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?