In the United States there are 142,386 public groundwater systems. The US Environmental Protection Agency (EPA) classifies them as community water systems (CWS), non-transient non-community water systems (NTNCWS) or transient non-community water systems (TNCWS).
The 40,000 groundwater CWS are public systems serving year-round populations and have an average user population of 2,200.
The non-community water systems (NCWS) serve much smaller populations, averaging 300 persons for the 18,000 NTNCWS and 134 persons for the 83,000 TNCWS.
These systems typically draw from wells to serve apartments, schools, trailer parks, rest stops and thousands of other applications, some serving commercial or even industrial water users.
Out of compliance
In January 2006, the US Environmental Protection Agency (EPA) reduced the maximum contaminant level (MCL) of arsenic in drinking water (sidebar, next page) to 10 micrograms per liter (µg/L) (or parts per billion [ppb]) from the previously existing 50 µg/L.
Although the new standard for arsenic was finalized in 2001 and mandated in 2002, it was estimated that 4,000 CWS were out of compliance when that standard was fully implemented in 2006. No estimates were made for compliance by the NCWS.
As McGuire Environmental Consultants, a water utility and treatment consulting firm based in Santa Monica, CA, pointed out in a white paper, “Small communities with limited resources will be the most heavily impacted by the new arsenic MCL. Many of these utilities will be transformed from a groundwater that simply chlorinates to a facility that uses advanced treatment technology in order to comply with a primary drinking standard. This will raise the required operator certification by a grade or more.”
The NCWS, with even less resources to commit to water treatment, will have a more difficult time meeting the MCL.
What these systems require are simple and inclusive programs for toxin removal that will meet the new MCLs with a minimum of cost to the users.
Guidelines for small systems
Here are some simple but important guidelines that will save small-system operators time and money in the installation, operation and maintenance of toxin removal systems — guidelines that water treatment professionals who work with these systems should be aware of:
1) The treatment system should be pre-engineered to save costs.
Often, engineering costs will exceed system costs for small-treatment configurations. A treatment system should be designed to be placed and plumbed, ready to go. Small systems do not and should not require extensive and potentially costly engineering studies. Installation should be a simple plumbing job with power only required for instrumentation.
2) The system should be redundant.
When dealing with toxins and health issues, redundancy reduces the chance of error and increases the viability of the system by 100 percent. Typically redundancy is achieved using media beds in a lead/lag configuration.
3) There should be no waste-to-drain requirements.
Most CWS and NCWS well sites have no access to waste drains nor are their system operators trained for wastewater operations. Shipping wastewaters off-site is expensive and time-consuming.
4) There should be no onsite production of residuals.
Toxin removal systems should not produce toxic or potentially toxic residuals on-site such as backwash waters or waste brines.
There are many regulations under RCRA, the Clean Water Act and the Safe Water Drinking Act that govern on-site production and subsequent disposal of wastes. Unskilled operators are not trained to deal with toxic byproducts of a backwash stream and could, without knowledge, violate a federal or state statute, putting a small water system at legal risk.
5) System simplicity is key.
Systems should not require pumps, backwash heads or other devices the failure of which would compromise the integrity of the treatment process. The more complications in the treatment process, the more likely a key component will fail and the higher the skill level required to operate the system. Systems should require minimal maintenance and operator input.
6) System life testing should be included in the treatment programs.
Most toxins in water are tasteless, odorless and invisible to the operator. Testing programs ensure the health and safety of the consumer. A testing program that monitors system performance also reduces operator liabilities and also maximizes media efficiency leading to reduced operating costs.
7) Media disposal.
It is important to remember that toxins are not “removed,” they are simply concentrated on treatment media as water comes into contact with the media, creating product water that is safe for consumption. The better the media, the longer it lasts. The longer it lasts, the more toxic substance it holds. As a result, the program should responsibly dispose of the spent media for the operator.
The regulatory environment concerning the disposal of toxins is still very fluid and operators should not be responsible for wastes disposal. Spent media is gaining more attention from regulators and the laws governing their disposal may eventually be subject to change. A small water system cannot afford to accept any long-term potential liability for discarded media should regulations change.
Affordable toxin removal
There are thousands of NCWS in the US out of compliance with the arsenic and uranium MCLs, as well as with other toxicity standards soon to be enforced.
Small CWS and NCWS do not have the fiscal or human resources for complicated toxin removal systems. A few treatment guidelines can make toxin removal affordable, easy to operate and simple to maintain and decrease operator liabilities.
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