Disinfection Byproducts (THM) Professor Jean MacRae Department of - - PowerPoint PPT Presentation

Disinfection Byproducts (THM)

Professor Jean MacRae Department of Civil and Environmental Engineering University of Maine

jean.macrae@maine.edu More info: http://oronoveaziewater.wordpress.com

TTHM = total trihalomethanes

• Cancer*

– Bladder, colon, rectal, liver

• Liver and CNS effects**
• Reproductive effects***

– Miscarriage, premature birth, low birth weight chloroform

*for chloroform 70-yr exposure to 6 ppb chloroform in drinking water increases fatal cancer risk by 1/1,000,000 *** High level exposures – animal studies ** High level exposures – humans

TTHM in our water over time

• Out of compliance

from fall 2011 to mid- 2013

• Lower values recently
• Average 69 ppb
• 27% higher than MCL

HAA = haloacetic acid

• Uptake is by ingestion

– Not skin or inhalation

• Health Effects

– Eye and skin irritation – Possible human carcinogen – Nerve, liver, immune damage – Reproductive effects

• RfD = 0.004 mg/kg-d
• MCL = 60 ppb (yearly

average)

– Testing since 2/2014, one value above MCL

Dichloroacetic acid

THM and HAA formation

Cl2 OM THM + HAA

Important Factors:

OM concentration Cl2 concentration Time Temperature

Where our water comes from

Why Chlorinate?

Does it have to be chlorine?

• Ozone
• Ultraviolet light
• Chloramine

– N product toxicity, higher dose

• Chlorine dioxide

– Chlorite and chlorate health effects, cost

Regulatory TTHM levels

EPA limits

• Maximum contaminant

Level (MCL) in drinking water – 80 µg/L

– OV water did not meet requirement for 1.5 years

• Reference Exposure Level

for inhalation = 300 µg/m3

• Reference Dose (RfD) –

0.01 mg/kg-day Air

http://www.epa.gov/ttn/atw/hlthef/chlorofo.html

𝐸𝑝𝑡𝑓 = 1.1 𝑀 𝑒 ∗ 0.07 𝑛𝑕 𝑀 + 15 𝑛3 𝑒 ∗ 0.007 𝑛𝑕 𝑛3 = 0.19 𝑛𝑕 𝑒

Estimate of Dose*

Average OVWD concentration 2005-2014 Typical daily water consumption Time averaged air concentration based on assumptions and using data from a study on THM exposure Typical daily volume air breathed/day 𝐸𝑏𝑗𝑚𝑧 𝐸𝑝𝑡𝑓 = 0.19 𝑛𝑕 𝑒 80 𝑙𝑕 = 0.0023 𝑛𝑕 𝑙𝑕 − 𝑒 𝑆𝑔𝐸 = 0.01 𝑛𝑕 𝑙𝑕 − 𝑒 Typical body weight About 1/4 of RfD *Estimate doesn’t include uptake through the skin or from swimming or other sources

𝐸𝑝𝑡𝑓 = 0.4 𝑀 𝑒 ∗ 0.07 𝑛𝑕 𝑀 + 5 𝑛3 𝑒 ∗ 0.007 𝑛𝑕 𝑛3 = 0.06 𝑛𝑕 𝑒

Estimate of Toddler Dose

Average OVWD concentration 2005-2014 Typical daily water consumption Time averaged air concentration based on assumptions and using data from a study on THM exposure Typical daily volume air breathed/day 𝐸𝑏𝑗𝑚𝑧 𝐸𝑝𝑡𝑓 = 0.06 𝑛𝑕 𝑒 11.4 𝑙𝑕 = 0.0057 𝑛𝑕 𝑙𝑕 − 𝑒 𝑆𝑔𝐸 = 0.01 𝑛𝑕 𝑙𝑕 − 𝑒 Typical body weight 57% of RfD

Reducing your exposure

• Take shorter showers
• Lower hot water heater temperature
• Ventilate when you use hot water:

– Bathroom fan – Above-stove fan (if it vents outside) – Open kitchen window

• Drink bottled water
• Kitchen faucet filter
• Whole house filter

– NSF, UL, ANSI certified for VOC removal

OVWD Treatment System

Storage Pump source water Storage and distribution Greensand Plus filters for Fe, Mn, OM removal Adjust pH Add permanganate and coagulant to help remove metals and OM Add chlorine for secondary disinfection (safety in distribution) Fluoride Add chlorine to regenerate the greensand filter media

What OVWD has done so far

• 1. Stopped using well 4 – mostly use

wells 1 and 3

– Lower OM and TTHMFP

• 2. Pipe flushing

– Lower time for reaction

• 3. Reduced dose of chlorine before the

filters

– Lower THM formation rate

• 4. Optimized coagulant dose

– Improve OM removal (and metals)

• 5. Change water loading rate on filters

1 5 4 3 2

More Ways to Prevent and Remove THMs

• New source with low OM
• Change oxidant and method for

filter regeneration

• Change disinfectant

– ClO2, chloramine

• Aerate and vent storage tanks
• Add OM or THM removal step

– Activated carbon – Coagulation/flocculation – Filtration

Action

• OVWD meetings: Tuesday October 14, 7 pm Orono council

chamber

– Advocate better communication – Strategic/long range plan to improve water quality – “same old” faces – PJ protest – Structure of OVWD – town council pressure to recall board members who are non-responsive – Submit questions to councils – get answers in writing from board – More content in meeting notes of OVWD – FOIA request (15 day response time) – Petition for municipal take over of WD – Test individual houses (ask council to pay $90/sample) – Live streaming (or video) of OVWD meetings? – Document attempted communication with board

**NC site had about 100 ppb in the water; TX site had about 25 ppb in the water (ours is in between at ~70 ppb) EHP 113:863-870 REL= 300 µg/m3