formation of thms and hans during brominationof

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

[email protected]

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).


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).



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

formation of thms and hans during brominationof

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