In urban sanitation systems, solid household wastes such as cotton and tea leaves pose a problem when disposed of in sinks primarily because they:

Correct Option

The correct option is

They obstruct drains and impede oxygen flow

Explanation

Urban sanitation systems are designed primarily to transport liquid wastewater and soluble waste. The disposal of non-biodegradable or slowly degrading solid materials into drainage systems disrupts the physical flow and biological processes required for effective waste management.

Option Analysis

• They release toxic chemicals into the water is Incorrect: Cotton and tea leaves are organic materials. While they decompose over time, they do not immediately release toxic chemicals into the water upon disposal.
• They obstruct drains and impede oxygen flow is Correct: Solid wastes such as used tea leaves, cotton, and soft toys do not dissolve in water. When disposed of in sinks, they accumulate in pipe bends and traps, causing physical blockages (choking the drains). Furthermore, these blockages restrict the free flow of oxygen within the sewage pipes. Oxygen is essential for the aerobic degradation of waste; obstructing its flow hampers the natural decomposition process.
• They dissolve rapidly and increase organic load is Incorrect: Unlike soluble substances (e.g., sugar or salt), cotton (cellulose) and tea leaves do not dissolve rapidly in water. They remain solid and contribute to physical obstruction rather than increasing the dissolved organic load immediately.
• They eliminate beneficial anaerobic bacteria is Incorrect: While the lack of oxygen might eventually shift the environment to an anaerobic one, the primary immediate problem is not the direct elimination of beneficial bacteria, but rather the physical obstruction and the prevention of oxygen circulation necessary for degradation.

Key Takeaway: Solid wastes like cotton and tea leaves must not be thrown in sinks because they choke drains and block the oxygen flow required for the degradation process.