Increased pH of permeate water in Reverse Osmosis plant with 25 m3/d capacity.

Hello All The pH input to the reverse osmosis system is7.5 While the pH of the output water (permeate) reaches 8.9. Note: 1- Only acidic antiscalants are injected. 2-This RO system designed in a room that its has a high temperature approximately in the range of 33-38 ° C. Questions: What is the cause of the pH increase? A- Temperature has increased the pH? B- Does microbial contamination can increase pH?(Chlorine injections have not been applied, which makes the water bad smell. membranes has also been infected with microbial contamination.)