145. Solving a chemistry problem

42. The MPC for phenol in natural water is 0.001000 mg / l. To determine phenols in water from formaldehyde resin production, 100.00 ml of water was diluted to 500.00 ml, passed through an activated carbon column, to remove impurities that interfered with the determination, then phenols were extracted in acidic medium, 4-aminoantipyrine was added to the extract, with which phenols at pH = 10.00 form colored compounds with an absorption maximum at λ = 460 nm. The optical density of the test solution is 0.160. The standard solution was prepared by dissolving 1.00 ml of solution with T (phenol) = 1,000 μg / ml in a volumetric flask with a capacity of 500.00 ml. The optical density of the standard solution, carried out through all stages of the analysis, was found to be 0.175. What is the concentration (mg / l) of phenol in wastewater? Is it possible to release it in a natural pond?