The correct option is (c).
Explanation
On-site sewage disposal systems are decentralized wastewater management solutions used to treat and dispose of effluent at or near the point of generation.
- Statement 1 is Correct: On-site sewage disposal systems, such as septic tanks, bio-toilets, and composting pits, are actively encouraged to improve sanitation in regions that lack centralized sewerage networks. They are essential for preventing open defecation and managing public health in rural or unplanned urban areas.
- Statement 2 is Incorrect: These systems primarily rely on biological decomposition (often anaerobic digestion by bacteria) rather than chemical treatment to suppress biogas. The process naturally results in the breakdown of organic matter, which produces biogas. The objective is waste treatment, not the strict prevention of biogas formation; in fact, technologies like bio-digesters are designed to facilitate this process.
- Statement 3 is Correct: The anaerobic decomposition of organic matter in sewage produces biogas, which consists mainly of methane and carbon dioxide. This biogas is a combustible fuel and can be harvested to serve as a source of energy for cooking, lighting, or electricity generation.
Key Takeaway: On-site sanitation systems utilize biological processes to treat waste in the absence of central infrastructure, often generating biogas as a valuable energy byproduct rather than suppressing it.