As per IS 10500:2012, the permissible limit of total dissolved solids (TDS), (in mg/l), in drinking water in the absence of an alternate source is:
2000
Understanding Total Dissolved Solids (TDS) in Drinking Water
Total Dissolved Solids (TDS) refers to the total concentration of dissolved substances in water. These substances can include minerals, salts, and organic matter. While some dissolved solids are harmless or even beneficial, high levels can affect the taste, odor, and appearance of water, and in some cases, pose health risks. Standards are set to ensure the quality and safety of drinking water.
IS 10500:2012 Standard for Drinking Water Quality
In India, the standard for drinking water quality is specified by IS 10500:2012. This standard lists various parameters and their recommended limits to ensure water is safe for human consumption. For many parameters, the standard provides two limits:
- Acceptable Limit: This is the preferred limit under normal circumstances.
- Permissible Limit in the Absence of an Alternate Source: This is a relaxed limit that may be tolerated only when no other source of water meeting the acceptable limit is available. Using water with parameters exceeding the acceptable limit but within the permissible limit should ideally be temporary.
TDS Limits According to IS 10500:2012
For Total Dissolved Solids (TDS), the IS 10500:2012 standard specifies the following limits:
- Acceptable Limit for TDS: 500 mg/l
- Permissible Limit for TDS in the Absence of an Alternate Source: 2000 mg/l
Analyzing the Question's Specific Requirement
The question asks for the permissible limit of TDS in drinking water *in the absence of an alternate source*, as per IS 10500:2012. This specifically refers to the second limit mentioned in the standard.
Based on the IS 10500:2012 standard, the permissible limit for total dissolved solids (TDS) in drinking water when an alternate source is not available is 2000 mg/l.
Let's look at the options provided:
- Option 1: 1000 mg/l
- Option 2: 500 mg/l (This is the acceptable limit, not the permissible limit in the absence of an alternate source)
- Option 3: 200 mg/l
- Option 4: 2000 mg/l
Comparing the standard value with the options, the value corresponding to the permissible limit in the absence of an alternate source is 2000 mg/l.
Therefore, as per IS 10500:2012, the permissible limit of total dissolved solids (TDS), in mg/l, in drinking water in the absence of an alternate source is 2000.
Revision Table: Key Water Quality Parameters (TDS Example)
| Parameter | Unit | Acceptable Limit (IS 10500:2012) | Permissible Limit in Absence of Alternate Source (IS 10500:2012) |
|---|---|---|---|
| Total Dissolved Solids (TDS) | mg/l | 500 | 2000 |
Additional Information on TDS and Water Quality Standards
High levels of TDS can be caused by natural sources like rocks and soil, or by human activities such as agricultural runoff, industrial wastewater, and sewage. While TDS itself might not be directly harmful, high concentrations can indicate the presence of other potentially harmful contaminants. Additionally, water with very high TDS might have an unpleasant taste (often described as mineralized or brackish) and can cause scaling in pipes and appliances.
The IS 10500:2012 standard is crucial for regulating drinking water quality in India, covering a wide range of physical, chemical, and microbiological parameters besides TDS. Regular testing and adherence to these standards are essential for public health.
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