Natural and Engineering Factors that Affect Disinfection Byproduct Concentrations in the Home Boning Liu and David Reckhow Department of Civil and Environmental Engineering, University of Massachusetts, Amherst, MA 01003
2 Intro & DBP Issue Factors affecting DBP formation Information Gaps Field Studies Design Municipal system Home impacts Conclusions Let’s make some disinfection byproducts!
HOCl + natural organics (NOM) Oxidized NOM and inorganic chloride Aldehydes Chlorinated Organics TOX THMs HAAs The THMs MCL 80µg/L The Precursors!
4 Raw water NOM levels (e.g., TOC) Specific precursor content of the RW NOM NOM removal Disinfection regime type & dose location in plant contact time & temperature pH Degradation and formation in DS
Water Heater City Water Drinking Showering & Washing Dermal & Inhalation Beverage Preparation Food Preparation Ingestion Ingestion & Inhalation Clothes Washing Dermal & Inhalation Ingestion & Inhalation Human Exposure Activity Major Routes Dish Washing Dermal & Inhalation EPA regulation based
Inhalation in the shower produces highest blood level and response is fast 6 Gordon et al., 2006 [Env. Hlth Persp.114: ]
Data from the Mills Plant (CA) August 1997 (courtesy of Stuart Krasner) Regulated DBPs But, the Bad Stuff is probably somewhere here
What is the extent of diurnal variations in regulated and non-regulated DBPs? In mains, near storage tanks, in dead ends How does actual exposure compare to expectations from compliance testing? Hot water effects(tankless vs. tank heater) Non-regulated DBPs
dd 9
Relatively low TOC 11
12 Recent DBP levels have dropped due to new WTP
Intensive sampling over 2 days Monitor cold water Plant effluent: system entry Distribution system location unaffected by storage and dead end Monitor hot water Measure regulated and non-regulated DBPs THMs, HAAs, residual chlorine, temp TOX, HANs, CP, TCP
Don’t try this at home
dsa 15 Field Site #1 Total transit time is around hours
temp 19
Northampton, MA
23 Percentage of Unknown TOX little changed 50% for cold water 45% for hot water
If TCAA decarboxylation isn’t the explanation, then what? Answer: Shift in reaction pathway for common THM/TCAA intermediate 24 THMsTriHAAs Simplified from: Reckhow & Singer, 1985 [Water Chlorination: Environmental Impact and Health Effects, Vol 5, pp ]
Key intermediate Concentrations are well known
Northampton, MA
Rocky Hill Cohousing Community, Northampton, MA Uniform construction: completed 2005 Study date: late July 2010 18 homes participated 8 tankless gas heaters, 10 conventional tank heaters
tankless heaters No storage tank On-Demand, save energy, how about Disinfection byproducts?
2 day sampling Temperature controlled Chlorine residual/pH measured at each site Samples quenched, cooled down and transported to lab for DBP analysis Simulated experiments
Reading is after flushing when temperature is stabilized Hot Water: C Cold Water: C
Heavy water usage
Delta value, ratio
Water Heaters substantially change the DBP levels and character Some increase many fold THMs, DiHAAs, Chloropicrin Some show little change TriHAAs Some decrease Dichloroacetonitrile, Trichloropropanone For most, we simply don’t know Tankless heaters have a smaller affect High temperatures shift reaction pathways TriHAA → THM Other products formed? What does this mean to exposure studies? Need to look at other DBPs and develop models Hypothesis: DBP increase is related to chlorine residual at time of heating 39
Northampton (MA) DPW - Water Division David Sparks, superintendent Alex Roseweir, Doug Ducharme, Paul Petersen Northampton Rocky Hill cohousing community 18 anonymous home owners 40
Total Chlorine Residual Mixed cold water from cohousing homes, incubated at 53 o C(average T of hot tap) Incubated water effluent from water treatment plant
TTHM DHAA THAA Immediately 53 o C
pH=6.7, temperature 60 o C, TCAA standard solution. Calculated K=( / )/hr
MCL: 60µg/L
47 Less than with the hot tap
48 Little difference between hot and cold
49 Higher terminal levels in cold tap