Alternative To Lowering Cooling Tower pH

Complete Water Solutions was tasked to assist a customer with alternatives to lowering the cooling tower pH to meet the state DNR discharge limits.

Current situation:
The customer had several cooling water loops and towers that are all tied together. The cooling water is used to cool metal treating and forming equipment. Recently the state DNR put a discharge high limit of 9 pH. With the current chemical treatment along with the incoming water source having a high pH it made it nearly impossible to hit the limit without some form of treatment.

Standard treatment to lowering cooling tower pH usual comes in the form of chemical treatment. Using such products as citric acid, or other acid’s to lower the over all pH or the discharge pH. The customer tried this and had a few issues. One being severe foaming and the other being a safety concern. With the limited staff to monitor the system along with limited time to deal with foaming issues the customer searched for another option.

We took some water samples to analyze, we also modeled Reverse Osmosis water as a blended make-up. Once the modeling had been completed, Complete Water Solutions was able to verify that Reverse Osmosis / Blended with soft water could provide a lower pH feed water thus eliminating the need for acid injection to help lower pH. There were also a few side benefits to using Reverse Osmosis Water, one of them was lowering the over TDS (Total Dissolved Solids), which increased the cycles in the tower, resulting in less blowdown.

The fleck 3150 carbon filter was a great choice as it met the flow requirements with minimal pressure loss when in operation. Also, these units are equipped with a lockout switch. This allows the carbon filter to backwash and shut down the Reverse Osmosis systems, after backwashing the RO systems will resume operation. The fleck 3150 has been a great product and has been around for many years.

The Osmonics Reverse Osmosis System has been the work horse of the industry for many years. The units selected here are equipped with cold water membranes allowing the unit to produce the designed flow rates @ 55 Degree F Water. Thus eliminating the need to pre-heat the water. The RO system comes with the Hanna Instrument Conductivity Mini Controller, along with the durable Tonkaflo Pump Model SS1823X. Later in 2019 Veolia will be announcing a Proflex option which will allow you to use a PLC to control the RO System.

The ro water is stored in a tank, from there it is pumped to feed the cooling loop. The pump selected was an Ebara ACDU pump with a 3 Phase Motor to help keep the AMP loading down. The ACDU pump is a stainless steel durable pump.