Disinfection Byproducts

MOST RECENT TTHM TEST RESULTS

Sample DateLocationTTHM (parts per million) LRAA (ppm)Regulatory Limit (ppm)
12/7/23925 Circuit Street425380
12/7/2370 Ponderosa Drive455580
12/7/232060 Washington Street486880
12/7/2324 Rockland Street132280

TTHM compliance with EPA regulations is based on the average analytical results for samples taken at a particular monitoring location during the previous four calendar quarters. This is referred to as the locational running annual average (LRAA)

Total Trihalomethane (TTHM) MCL Violation

In the past 30 years, the Safe Drinking Water Act (SDWA) has been highly effective in protecting public health and has also evolved to respond to new and emerging threats to safe drinking water. Disinfection of drinking water is one of the major public health advances in the 20th century. One hundred years ago, typhoid and cholera epidemics were common through American cities; disinfection was a major factor in reducing these epidemics.

However, the disinfectants themselves can react with naturally-occurring materials in the water to form byproducts, which may pose health risks. One of these by-products is total trihalomethanes (TTHMs). In June of 2015, the Hanover Water Department exceeded the drinking water standard for TTHMs as established by the Environmental Protection Agency (EPA). That standard is set at 80 parts per billion (ppb). A sample tested in June of 2015 had a TTHM level of 84.3 ppb. As a result, the Town of Hanover had issued a public notice regarding this violation of the EPA standard for TTHMs in our drinking water. Some people who drink water containing TTHMs in excess of the Maximum Contaminant Level (MCL) over many years could experience liver, kidney, or central nervous system problems and increased risk of cancer.

Amendments to the SDWA in 1996 required the EPA to develop rules to balance the risks between microbial pathogens and disinfection byproducts (DBPs). These rules will reduce potential cancer and reproductive and developmental health risks from disinfection byproducts (DBPs) in drinking water. Over 260 million individuals within the United States are exposed to DBPs. The EPA has projected that current SDWA regulations will prevent approximately 280 bladder cancer cases per year. To protect public health, EPA continues to strongly support both the disinfection of drinking water to reduce the risk of waterborne disease and the reduction of disinfection byproducts. EPA has regulated DBPs since 1979 to address health risks posed by a potential association between chlorinated drinking water and cancer, particularly bladder cancer. Current reproductive and developmental health effects data do not support a conclusion at this time as to whether exposure to chlorinated drinking water or disinfection byproducts causes adverse developmental or reproductive health effects, but do support a potential health concern.

Correcting the Problem

The Town meeting authorized funding to make treatment improvements including conversion of older chlorination systems to safer liquid based systems, conversion of free chlorine to chloramines through the use of liquid ammonium sulfate, updates to chemical feed and chemical storage systems, upgrades to controls, and the installation of water storage tank mixing systems.  These improvements were completed in the winter of 2020 and went on-line in the spring of 2020.  We are pleased to report that as expected the improvements have reduced the total trihalomethanes to acceptable levels.

The table below lists the total trihalomthane (TTHM) test results since 2018.  

Total Trihalomethane (TTHM) Test Data

 HFD #3 - 925 Circuit St70 Ponderosa Drive2060 Washington St24 Rockland St, unit 8
1st Qtr. 201840515621
2nd Qtr. 2018989310372
3rd Qtr. 2018103102104103
4th Qtr. 20181071177313
1st Qtr. 201937522225
2nd Qtr. 201953807227
3rd Qtr. 2019921189583
4th Qtr. 201965814352
1st Qtr. 202063564532
2nd Qrt. 202036412613
3rd Qrt. 202024432832
4th Qtr. 202042463237
1st Qtr. 202118191714
2nd Qtr. 20214039508
3rd Qtr. 2021111118120123
4th Qtr. 202152706259
1st Qtr. 202221232120
2nd Qtr. 202245425452
3rd Qtr. 202250484533
4th Qtr. 202254534848
1st Qtr. 20232325308
2nd Qtr. 202347468151
3rd Qtr. 20239910411418
4th Qtr. 202342454813

Compliance with the Federal Safe Drinking Water Act is based on a locational annual running average at a particular test site.  This means that the average of the past four values at any particular site must be below 80 ppb  (parts per billion).  The table below lists the locational running averages for each of the town's four sites.  The numbers in red show the periods in which the locational running average exceeded the federal action level.  Note that all numbers are now well below the action level.

Total Trihalomethane (TTHM) Compliance Data

 HFD #3 - 925 Circuit St70 Ponderosa Drive2060 Washington St24 Rockland St, unit 8
1st Qtr. 201853733617
2nd Qtr. 201859735933
3rd Qtr. 201872768355
4th Qtr. 201887918452
1st Qtr. 201986917653
2nd Qtr. 201975886842
3rd Qtr. 201972926637
4th Qtr. 201962835847
1st Qtr. 202068846449
2nd Qtr. 202064745245
3rd Qtr. 202047553632
4th Qtr. 202041473329
1st Qtr. 202130372624
2nd Qtr. 202131373223
3rd Qtr. 202153565546
4th Qtr. 202155626251
1st Qtr. 202256636353
2nd Qtr. 202257636464
3rd Qtr. 202242464541
4th Qtr. 202242414238
1st Qtr. 202343424435
2nd Qtr. 202343435135
3rd Qtr. 202356576831
4th Qtr. 202353556822

We will continue to monitor the TTHM values from our four test sites on a quarterly basis and will report the results here as they become available.

In addition, whenever water chemistry changes, there is the risk of unintended consequences.  We are monitoring the distribution system for lead and copper as well as nitrates and will report the results here as they become available.  So far all systems are operating as expected. 

Click here for frequently asked questions and answers regarding chloramines

Haloacetic Acids (HAA5)

Haloacetic acids (HAA) are a group of disinfection byproducts that form when chlorine compounds that are used to disinfect water react with other naturally-occurring chemicals in the water.  There are five significant HAA potentially found in disinfected drinking water and their combined concentration is referred to as Total HAA5.

Levels of HAA5 can be affected by seasonal changes in source water quality or by changing amounts of disinfection added.  Water systems often can experience temporary increases in HAA5 due to short-term increases in chlorine disinfection.  Chlorine disinfection increases can occur when there is a water main break, when water systems are under repair, or when there is a potential microbial (example: bacteria) problem or threat.

All water systems that use chlorine to disinfect the water are required by federal and state law to sample for HAA5 on a regular basis (quarterly, or once every three months).

The table below lists the total HAA5 test results since 2018. 

Haloacetic Acid (HAA5) Test Data

 HFD #3 - 925 Circuit St70 Ponderosa Drive2060 Washington St24 Rockland St, unit 8
1st Qtr. 2018115167
2nd Qtr. 201825102529
3rd Qtr. 20181211814
4th Qtr. 201888346
1st Qtr. 20191515163
2nd Qtr. 20190123410
3rd Qtr. 2019064329
4th Qtr. 2019873229
1st Qtr. 2020731310
2nd Qrt. 202025292711
3rd Qrt. 202014211918
4th Qtr. 202032283033
1st Qtr. 20211218125
2nd Qtr. 20213738567
3rd Qtr. 202164518072
4th Qtr. 202123102425
1st Qtr. 20226376
2nd Qtr. 202220132135
3rd Qtr. 20221851914
4th Qtr. 20222562728
1st Qtr. 202357103
2nd Qtr. 20232184119
3rd Qtr. 202319145512
4th Qtr. 202372244

Like TTHMs, HAA5 compliance with the Federal Safe Drinking Water Act is based on a locational annual running average at a particular test site.  This means that the average of the past four values at any particular site must be below 60 ppb  (parts per billion).  The table below lists the locational running averages for each of the town's four sites.

Haloacetic Acid (HAA5) Compliance Data

 HFD #3 - 925 Circuit St70 Ponderosa Drive2060 Washington St24 Rockland St, unit 8
1st Qtr. 20185787
2nd Qtr. 20181061313
3rd Qtr. 20181371414
4th Qtr. 20181492114
1st Qtr. 201915112113
2nd Qtr. 2019911238
3rd Qtr. 20196103212
4th Qtr. 20196103118
1st Qtr. 2020473120
2nd Qtr. 202010112920
3rd Qtr. 202013152317
4th Qtr. 202020202218
1st Qtr. 202121242217
2nd Qtr. 202124262916
3rd Qtr. 202136344529
4th Qtr. 202134294327
1st Qtr. 202233264228
2nd Qtr. 202228193335
3rd Qtr. 20221781820
4th Qtr. 20221771821
1st Qtr. 20231781920
2nd Qtr. 20231762416
3rd Qtr. 20231793315
4th Qtr. 20231383310

 

Disinfection Byproducts Test Data