<prompt> Nitrates in drinking water indicate:-Recent pollutionRemote pollutionRadioactivityColiforms  <response>: Nitrates in drinking water indicates: Remote contamination. Nitrites in drinking water indicates: Recent contamination. Guidelines of drinking water quality in India: Colour 15 TCU Turbidity 1 NTU Hardness 100-300 mgL pH 6.5- 8.5 TDS 500 mgL Fluorides 1ppm Nitrates 45 mgd Nitrites 3 mg d Radio-activity: alpha 0.5 BcqL ; Beta 1.0 BcqL. Extra edge: - Turbidity of water is visible to naked eye when its 4 NTU. 