Which waste can go into a Class 1 system?

• A. Biodegradable kitchen wastes
• B. Human body waste
• C. Non-biodegradable plastics
• D. Hazardous chemicals

Answer: (B)

Class 1 onsite systems are designed to treat domestic wastewater from a single household, relying on a septic tank to biologically break down waste contents produced by toilets and other regular household uses. Human body waste fits this purpose because it is readily biodegradable and releases organic matter that the tank’s anaerobic digestion can process, producing a relatively stable effluent for the drain field.

Biodegradable kitchen wastes, while they can decompose, add large amounts of solids, fats, and oils that can overwhelm the system, clog the outlets, or disrupt the balance of microbial activity, so they’re generally not intended for a Class 1 system. Non-biodegradable plastics won’t break down at all and can accumulate, causing blockages and other problems. Hazardous chemicals can kill the beneficial microbes in the tank and contaminate soil and groundwater, so they must be kept out of on-site systems. So, the waste that belongs in a Class 1 system is human body waste.