The Neutralizer is a two-stage chemical treatment system. Untreated biosolids, usually consisting of Waste Activated Sludge (WAS), travel through the Neutralizer system where they are treated by a patented chemical injection system. The processing time is eight hours and the final product is a treated, odor-free residual suitable for use as a commercial fertilizer.

The Neutralizer® Process


Step 1 – Sludge Delivery & Thickening

WAS Pumps feed sludge from the clarifier, typically at 1-2% solids, into the Neutralizer Sludge Receiving & Polymer Addition Skid at a monitored and controlled rate. The polymer injection system adds polymer to the sludge to optimize thickening. The sludge and dilute polymer mixture is sent to the stir/flocculation tank on the Sludge Thickening Skid where Huber disk thickeners thicken the sludge to 4% solids. Thickened sludge is then sent to the sludge hopper where it accumulates for chemical treatment.

Step 2 – Neutralizer® Chlorine Dioxide Addition & Acidification

Sludge is pumped from the sludge hopper to the Sludge Processing Skid where chemical metering pumps deliver flow-controlled doses of sodium chlorite and sulfuric acid into BCR’s chlorine dioxide (ClO2) Generating System, a patented technology for onsite production of chlorine dioxide. The system then injects the chlorine dioxide into the thickened sludge stream and pumps the mixture into the Sludge Processing Tanks. The sludge is retained in the Sludge Processing Tanks for at least one hour.

Step 3 – Neutralizer® Sodium Nitrite Addition & pH Adjustment

In the second stage of chemical treatment, sulfuric acid (H2SO4) is pumped into the Sludge Processing Tanks, dropping the pH to an optimal level. Then, sodium nitrite (NaNO2) is added to the Sludge Processing Tanks for an additional six hours to ensure the required pathogen reduction for Class A/EQ and Volatile Solids Reduction (VSR) for Vector Attraction Reduction (VAR) are met. Prior to dewatering, sodium hydroxide (NaOH) is added to the disinfected sludge in to raise the pH of the final product, typically to a pH of 6.0 to meet the end user’s needs.

Step 4 – Dewatering & Phosphorus Removal

Neutralizer treatment enhances dewaterability, resulting in reduced polymer consumption and higher total solids in the end product, which in turn leads to reduced operating and hauling costs. The Class A/EQ residuals are dewatered using standard technology such as a centrifuge, screw press, or belt press. Ferric sulfate (Fe2(SO4)3) is added to the disinfected sludge immediately prior to dewatering to aid in phosphorous removal. Phosphorous binds with the iron in the ferric sulfate and this iron phosphate is retained within the dewatered residuals, effectively removing phosphorus from the wastewater treatment facility.

Step 5 – End Product Management

Neutralizer produces superior Class A/EQ residuals that allow for expanded disposition options based on their nutrient content and lack of foul odors. As part of our Whole Solution offering, BCR can assume long-term responsibility for the transportation and end product management of material treated at any Neutralizer facility, eliminating client liability for end product management and disposition.