20-1210 Use of Hydrogen Peroxide for Water Treatment

QUESTION

As a means to integrate closed loop water cycles we are treating grey and black water and reintegrating it into the system, either for WC or for irrigation, with all excess water overflowing and directed into the lake system.

For this reason we are required to treat water according to standards for water with "direct human contact" according to NOM-001-SEMARNAT and NOM-003-SEMARNAT from the Mexican water treatment code.

When water is used within a building it is directed to a USBF [Upflow Sludge Blanket Filtration] treatment plant. Solids are separated and water enters an artificial wetland. At the end of the wetland water is pumped into two cisterns, one for WC reuse and one for irrigation. From the wetland to the cistern, water is cleaned in-line through micro dosing with hydrogen peroxide.

These measures allow us to have water quality for human contact according to standards. We acknowledge hydrogen peroxide is a chemical but compared to sodium hypochlorite or chlorine dioxide it does not present known carcinogenic risks.

For this reason we are requesting an exception towards using hydrogen peroxide in small doses (±0.3%) for water treatment.

ANSWER

Because it is required by code, and because at the cited concentration and application, it is not expected to pose a risk to human health, and because, according to supplementary information provided by the team, any overflow of the treated water in the cisterns will be routed back through the treatment wetland to provide for dissipation of the hydrogen peroxide, the team may treat water for human contact with hydrogen peroxide as required by the country's water code, according to the following modification to exception WT-005 Chlorine Disinfection, which is being re-titled Chemical Disinfection:

WT-005 Chemical Disinfection
Use of the chemicals listed below is allowed if required by the authority having jurisdiction. In all cases, the amount of chemical added must be the minimum allowed by the jurisdiction. 

Project teams using this exception will need to provide evidence that the treatment is required by the jurisdiction having authority, identify required concentrations, and provide a narrative with diagrammatic description of the treatment system, including operation details demonstrating that only the minimum quantity of chemical allowed by code is being used, and that concentrations otherwise meet requirements as indicated in the specific exception requirements for each chemical.

The following additional requirements apply for each allowed chemical:

Chlorine
The project must include and document point-of-use dechlorination with a 0.5-micron carbon block filter or other approved dechlorination method for all potable end uses.

Hydrogen Peroxide
Where treatment is required to be added at the point of storage, and the storage container has an overflow outlet, residual concentrations of the hydrogen peroxide must be dissipated prior to release of the overflow into any non-treatment aquatic habitat. Documentation of the water system must address, with written confirmation by the system designer, how the hydrogen peroxide breakdown will occur prior to overflow dispersal into aquatic habitat.

Documentation Requirements:
I06-a Exception Narrative
Signed narrative statement making a clear case that the project is eligible for the Exception and how it has met requirements.

I06-c Design Documentation
Design documents, such as project manual excerpts, drawings, cutsheets, or calculations, showing how the project meets exception requirements with specific reference to the concentrations and the systems affecting those concentrations at points identified in the exception.

Note that with this modification, the exception requirement in LBC 3.1 to appeal the jurisdiction's requirement for chemical treatment has been removed. 

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