Which of the following are examples of Alternative Systems?

Alternative systems are used for wastewater treatment when traditional septic systems are not suitable, typically due to site conditions like poor soil permeability, high groundwater levels, or insufficient space.

Mounds, single pass sand filters, and recirculating gravel filters are all recognized methods of wastewater treatment that fall under the category of alternative systems. Mounds involve creating an elevated soil bed to facilitate treatment in a manner that allows for effective drainage and eventual absorption into the surrounding environment. Single pass sand filters utilize layers of sand to treat wastewater as it flows through, relying on the filtration properties of the sand to remove contaminants. Recirculating gravel filters similarly treat wastewater by utilizing gravel as a medium to filter and treat the effluent more effectively than conventional systems.

The correct answer encompasses all these types of systems, indicating that they share the characteristic of providing alternative means of wastewater management in various situations where traditional methods may fail or be inadequate. Each of these systems serves to ensure that effluent is properly treated before being released into the environment, showcasing the diversity and adaptability of alternative wastewater treatment solutions.