Algal-derived organic matter as precursors of disinfection by-products and mutagens upon chlorination

Algal-derived organic materials (including algal cells, hydrophilic and hydrophobic proteins) from Chlamydomonas sp. (a common green alga in local reservoirs), were chlorinated in the laboratory (20 degrees C, pH 7, Cl-2/DOC ratio of 20 mg Cl-2 mg(-1)). Levels of disinfection by-products and mutagenicity (via Salmonella 1100 mutation assay, -S9) over 2 h of chlorination time were determined. The hydrophilic proteins were more effective precursors of chloroform (35.9 mu mol L-1 at 120 min), 35 times greater than that from the hydrophobic proteins; whereas the hydrophobic proteins were more potent precursors of direct-acting mutagens (maximum level of 50.1 rev mu L-1 at 30 s) than the hydrophilic proteins (maximum level of 3.38 rev mu L-1 at 60 min). The mutagenicity of the chlorinated solutions generally reached a peak level shortly after chlorination and then declined afterwards, a pattern different from that of chloroform generation. The results indicate that algal hydrophilic proteins, containing low aromaticity and difficult to be removed via coagulation/flocculation, are important chloroform precursors. It is also suggested that hydrophobic organic intermediates with low molecular weight formed during chlorination may serve as the direct-acting mutagens. (C) 2010 Elsevier Ltd. All rights reserved.