Sewage vs. Sullage — What's the Difference?

Sewage is a type of wastewater that is generated from residential, industrial, commercial, or agricultural activities. It contains a wide variety of pollutants including human waste, food scraps, oils, soaps, and chemicals. On the other hand, sullage, also known as greywater, emanates primarily from domestic processes such as dishwashing, laundry, and bathing, excluding any human waste.

Sewage systems are designed to transport this wastewater to treatment facilities where it can be processed and either released into the environment safely or reused. Whereas sullage, being less contaminated, can be reused with minimal treatment for gardening and irrigation, highlighting differences in management and treatment approaches.

The treatment of sewage often requires complex and multi-stage processes due to the presence of harmful pathogens and chemicals. These processes can include primary, secondary, and tertiary treatments to remove solids, organic matter, and nutrients. Sullage, however, may only need basic filtration and disinfection before it can be considered safe for certain types of reuse, reflecting its lower level of contamination.

Regulations regarding the disposal and treatment of sewage are typically stricter compared to those for sullage. This is because sewage poses a greater risk to public health and the environment due to its composition. Sullage regulations are often less stringent, recognizing its potential for reuse and lower health risks.

Understanding the distinction between sewage and sullage is crucial for effective water management and conservation strategies. By treating and reusing sullage for non-potable purposes, communities can reduce the demand on freshwater resources, while sewage treatment prevents the spread of diseases and environmental degradation.