Fourth National Cyanobacterial Workshop
Formation of THMs and HANs during
bromination of Microcystis aeruginosa.
Shanghai National Engineering Research Center of Urban Water Resources
Sep. 23, 2014
Ning Lu
Bromine-containing disinfectants, DBDMH (2,4-dibromo-5,5-dimethylhydantoin)
and BCDMH (bromo-3-chloro-5,5-dimethylhydantoin), are widely used for
recreational water and drinking water purification.
Bromide (Br-) in water could be oxidized to free bromine (Br2) by commonly
used disinfectants, such as chlorine or ozone.
Algae elevate TOC/TON in water, result in high formation risk of DBPs.
A brief introduction to Qingcaosha (Qcs) Reservoir
Investigation of bromide and algae in raw water from
Qcs Reservoir.
DBPs formation potential in Microcystis aeruginosa
solutions during bromination.
The largest reservoir as drinking water resource in China: 66.15 km2;
7,510,000 m3/d; available capacity: 524,000,000 m3/d
( 68 days continuous supply of drinking water for 13 millions people)
Costal: locates at Yangtz river estuary
Shallow: 2-14 m depth
.
bromide vs. conductivity & chloride,
respectively
bromide in the influent and effluent
(2012-2013)
90 μg/L
Outlet gate
Algae intensity of the influent and effluent (2013)
Typical algae species in Qingcaosha reservoir
Synedra sp.
Cyclotella sp.
Tetrastrum elegans
Pediastrum duplex
The ratio of Microcystis to all algae in water
samples (July, 2013- Nov, 2013)
Microcystis in water samples
Microcystis aeruginosa solutions during bromination
Experimental setup: 25 ºC, 48 hr, dark conditions, amber bottles (glass),
10 mg/L disinfectants, 5 mgTOC/L algae solution. Free bromine was
prepared by AgNO3 -Br2 titration method (4 ºC).
Microcystis aeruginosa solutions during bromination
Bromine IncorporationFactor
BIF=0 BIF=3
BIF=2.58
BIF=2.82
Experimental setup: 25 ºC, 48 hr, dark conditions, amber bottles (glass),
10 mg/L disinfectants, 5 mgTOC/L algae solution. Free bromine was
prepared by AgNO3 -Br2 titration method (4 ºC).
Microcystis aeruginosa solutions during bromination
Microcystis aeruginosa solutions during bromination
Microcystis aeruginosa solutions during bromination
Experimental conditions Cytotoxicity
HOBr 0.28mmol/L
pH=5 0.0173
pH=7 0.0606
pH=9 0.0418
HOCl 0.28mmol/L pH=7 0.0007
HOCl 0.28mmol/L +Br-
0.14mmol/LpH=7 0.0243
HOCl 0.14mmol/L +HOBr
0.14mmol/LpH=7 0.0533
Cytotoxicity EC50(mol/L): CF 9.1E‐3, BDCF 9.1E‐3, DBCF 5.2E‐3, BF 4.0E‐3, DCAN 5.8E‐5, TCAN 1.7E‐4, BCAN 8.4E‐6, DBAN 2.9E‐6.
Toxicity=Σ(Ci/EC50i)i=1,n
Bromide and algae are the two main issues of Qingcaosha reservoir. Seawater
intrusion greatly elevates the bromide level.
Bacillariophyta is the dominant species in cold weather, while cyanophyta is the dominant species in summer.
Brominated THMs and HANs were generated by applying bromine-containingdisinfectants to inactivate Microcystis aeruginosa.
The molar production of total THMs in free bromine disinfection was nearly same as that of chlorine.
The presence of free bromine drastically elevated the cytotoxicity of the
formed disinfection by-products.
Thank you