Where should backwash water be directed in a DIS?

The backwash water in a Decentralized Treatment System (DIS) should be directed to the building sewer at the inlet of the pretreatment tank. This is important because directing backwash water here ensures that the water is properly treated along with other household wastewater before it enters the main septic system. By sending it to the pretreatment tank, any solids, organic matter, or contaminants present in the backwash water can be adequately treated, allowing for better overall system performance and reducing the risk of clogging or overloading the septic infrastructure.

In contrast, directing backwash water to a ditch could lead to environmental contamination and mishandling of waste, as this water is not treated and may contain harmful substances. Sending it to a garden area is also inappropriate, as this could pose a health risk to plants and people, and may violate local regulations regarding wastewater disposal. Lastly, directing it to a separate filtration area may complicate system design and management without ensuring that the water is adequately treated before it re-enters the primary wastewater management system. Thus, directing backwash water to the inlet of the pretreatment tank is the most responsible and effective method for managing this type of wastewater.