What is the primary purpose of sending samples collected under Section 21 of Water Pollution Act to a laboratory?

Section 21 – Power to take samples of effluents and procedure to be followed in connection therewith Authority to Take Samples • The State Pollution Control Board (SPCB) or any authorized officer has the power to collect samples of: o Water from any stream or well. o Sewage or trade effluents discharged from any plant, vessel, or establishment into a stream or well. Admissibility in Legal Proceedings • The analysis results of the samples cannot be used as legal evidence unless the procedure outlined in sub-sections (3), (4), and (5) is strictly followed. Step-by-Step Procedure for Sampling 1. Issuing a Notice o Before taking the sample, the officer must serve a notice (in a prescribed format) to the occupier (person in charge of the facility) or their agent. 2. Dividing the Sample o The collected sample must be divided into two parts in the presence of the occupier or agent. 3. Sealing and Signing the Sample o Each part of the sample must be placed in a container, which is then sealed and signed by both:  The officer collecting the sample.  The occupier or their agent. 4. Sending the Sample for Analysis o One part of the sample is sent immediately to a recognized laboratory for testing:  For Union Territories: The sample goes to a Central Board-recognized laboratory (Section 16).  For States: The sample is sent to a State Board-recognized laboratory (Section 17). o The second part is sent to a separate laboratory upon the occupier’s request:  For Union Territories: Laboratory specified under Section 51(1).  For States: Laboratory specified under Section 52(1). Provision for Absence of the Occupier or Agent • If the occupier or agent is absent despite being served a notice: o The officer collects, seals, and signs the sample alone. o The sample is sent to the designated laboratory for analysis.