Volume 19   |   Issue 3   |   September 2017

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Sustainable packaging and why it is growing in importance

Floor Care – Green to Sustainable

Toilet to Tap Part 2

Letter from the Editor

Sustainability Resources

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Toilet to Tap Part 2

Addressing the “Ick” Factor

By John Chambers, Rochester Midland Corporation

In the last installment of the Water Energy Division’s Sustainability e-Newsletter, the concept of “Toilet to Tap” was introduced.  “Toilet to Tap” or Direct Potable Reuse bypasses the normal release of treated sewage effluent into lakes, rivers and streams as a step in potable water production cycle.  Instead, treated effluent from the sewage treatment plant flows directly into the potable treatment process.  This potable treatment option is actually more sustainable than the current model in use in thousands of drinking water plants across the US and will become more prevalent in areas where water is scarce.  The only real issue with this method of drinking water production is the “ick factor” (public perception).  People have a difficult time getting past the direct reuse of treated sewage effluent.  Understandable, but when the science and technology behind direct potable reuse are considered, this is not a bad idea.  Actually, the treated water quality from DPR is higher and the real-time monitoring ensures greater safety for the consumer.

The US Environmental Protection Agency mandates that compounds that could harm the environment be eliminated or limited to very low levels in treated sewage effluent.  There are two lists of pollutants that must be managed, including:

Section 401.15 - Toxic pollutants - Link: https://www.gpo.gov/fdsys/pkg/CFR-2014-title40-vol29/xml/CFR-2014-title40-vol29-sec401-15.xml

Appendix A to Part 423 - 126 Priority Pollutants - Link: https://www.gpo.gov/fdsys/pkg/CFR-2014-title40-vol29/xml/CFR-2014-title40-vol29-part423-appA.xml

These two lists contain specific chemicals or chemical groups that must be eliminated prior to discharge including: solvents, pesticides, PCBs, and metals.  In addition, regulations mandate the use of oxidizing biocides for the destruction of pathogenic bacteria that would be left in the treated effluent.  Sewage treatment plants are capable of removing most of the contaminants with the exception of some environmentally persistent pharmaceutical pollutants (EPPP).  Some portion of these materials resists consumption by bacteria in the treatment plant and/or is not destroyed by oxidizers used for disinfection.  Most EPPP’s are still unregulated and science is just beginning to understand the effects they have on the environment and people.

So, after treatment at the sewage treatment plant, the effluent quality is deemed appropriate for discharge to water bodies that contain animal and plant life.  Additionally, the mixed effluent (treated effluent and native water) becomes the influent water to potable drinking water plants downstream.  There will be some further natural degradation of the EPPP’s due to UV radiation and natural biological respiration.  However, some of the material will remain intact and the potable plant cannot remove these materials as they are soluble (in solution and too small to be captured by typical filtration methods).  It should be noted that potable plants use filtration down to 2-5 microns to remove solids and oxidation to kill germs.  Soluble organic materials like EPPP’s are in the range of less than .45 microns in size; consequently, they get back into the drinking water system. 

What does this mean for drinking water provided by a municipality?  Potable water can contain metals up to a limit imposed by the EPA or even lower if a state wants to enforce a stricter protocol.  Drinking water can also contain small amounts of many other harmful substances.  The EPA list of contaminants and limits is available at the link below:

Table of Regulated Drinking Water Contaminants - Link: https://www.epa.gov/ground-water-and-drinking-water/table-regulated-drinking-water-contaminants

Testing for contaminants occurs on a routine basis and each facility must report its results to the EPA and to the public.  For the most part, public water is very safe to consume and records for each utility can be reviewed to provide added assurances.  However, chemical spills, contamination and natural disasters do happen.  It is always prudent to filter public water through a Carbon filter, as a minimum, for regular home use.  Carbon will remove any Chlorine or Chloramines used to disinfect the water and eliminate any risks associated with these chemicals; taste will also improve dramatically.  For an added layer of safety in the case of contamination or natural disaster it also advisable to install a reverse osmosis filtration system on any faucet that will be used for drinking water.  Reverse osmosis (R/O) technology uses a filter membrane under high pressure to produce water of nearly distilled water quality.  Some very small ions like Sodium (Na) can slip through the filter at low levels, but most other ions, bacteria and organic materials are rejected.  With use of this filtration method, virtually all risks from a public water source can be eliminated.

Reverse Osmosis technology, as described above, virtually eliminates risks associated with potable water contaminants.  This technology has been on the market for 20-30 years and much like computers, the prices have come down and the filters have become more efficient.  This technology also happens to be the reason that Direct Potable Reuse is now a viable option.  Treated sewage effluent can move directly to the potable treatment process because reverse osmosis filters and the associated monitoring technology have made it possible to reliably produce near distilled water quality drinking water.  Permeate (filtered water) from the R/O membrane is lower in contaminants than 99% of the treated potable water available across the country.   With TDS (total dissolved solids) and TOC (total organic carbon) monitoring, via real-time data, verifying the condition of the finished water ensures that the water is always free of contaminants.

In summary, direct potable reuse of sewage effluent is a viable and sustainable option for many communities with water scarcity concerns.  The real costs associated with pumping water many miles and the electricity necessary to power the pumps plus the carbon emitted into the environment with the use of fossil fuels must be considered.  With DPR, the cost of the R/O unit and the electricity to pressure the filter pumps must be considered; not to mention the capitol cost of the monitoring equipment.  The profit leg of the “sustainability stool” is the generally the shortest with this technology.  However, the people and planet legs are notably sturdy and of the proper length.  People enjoy consistently high quality water that is much less likely to contain contaminants like metals, organics, EPPP’s, or bacteria as these items are rejected by reverse osmosis membrane.  In addition, much less oxidizing biocide like Sodium Hypochlorite or Chloramine is needed because the bacteria and organics have been removed.  Finally, the DPR process is better for the planet.  Environmentally Persistent Pharmaceutical Pollutants are never released back into the environment where they can cause bizarre problems to develop with aquatic life.  “Toilet to Tap” or Direct Potable Reuse is a viable and more favorable option for many communities facing water scarcity.  This technology is currently in use and will continue to grow provided that “ick factor” is addressed.  Please forward comments or questions regarding this installment to John Chambers