The correct option is (c) 2 and 3 only.
Explanation
Sewage disposal involves the collection, treatment, and safe discharge of wastewater. In areas where centralized underground sewerage systems are absent, alternative onsite sanitation methods are utilized to manage human waste and prevent environmental contamination.
Statement-wise Analysis:
- Statement 1 is Incorrect: Low-cost onsite sewage disposal systems are not banned. Instead, they are actively encouraged and adopted in areas where sewerage systems are unavailable to ensure sanitation and prevent open defecation.
- Statement 2 is Correct: Onsite systems treat sewage at the point of generation. Septic tanks, chemical toilets, composting pits, and vermi-processing toilets are standard examples of low-cost onsite sewage disposal systems.
- Statement 3 is Correct: Open drains often lead to the stagnation of wastewater. These stagnant pools serve as breeding grounds for mosquitoes, facilitating the spread of vector-borne diseases such as malaria and dengue.
Key Takeaway:
Onsite disposal systems like septic tanks and vermi-processing toilets are vital sanitation solutions in the absence of sewerage networks, whereas open drains pose significant public health risks by promoting vector breeding.