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.)
While some of previous answers have merit, it could be your membranes are plumbed wrong and you're actually getting concentrate or a portion of it from the permeate side. Your pH should always be reduced after passing thru an RO! Have you checked both permeate and concentrate sides for TDS and pH?
RO permeate is acidic normally if no pH adjustment. Therefore, microbial contamination is likely the case. Please check the physical condition of membrane whether it is slimy or pressure build up.
I believe the pH may have increased as a result of some microbial effect, similar to the increase of pH when the algae strip out the carbon atom from alkalinity sources resulting in producing the hydroxyl ion, and consequently increasing the pH. The Bad odour may be associated with Grosmin or MIB in the final water.
It depends on the TDS of permeate. If the TDS is high water will evaporate and pH will increase. What is the temperature of permeate. At warm conditions even the microbial activity is increase .This also could a possible reason.