Characteristics and Reactivity of Algae-Produced Dissolved Organic Carbon

Algae (green, blue-green, and diatom) grown in inorganic media produced particulate and dissolved organic carbon (DOC). DOC produced by a green-alga contains 25% hydrophobic acids. DOC from all algae had specific ultraviolet absorbance values less than 2.0  m-1  (mg/L)-1. Algae-produced DOC was biologically labile; greater than 60% degraded in bioreactors within 5 days. The biodegradable material likely included carbohydrates, amino acids, and amino sugars, which were present in hydrophobic acid isolates. Chlorination of algal DOC formed disinfection by-products; DOC from the green alga, Scenedesmus quadricauda, produced chloroform [0.53  micromole  per  mg  carbon  ((mu)mol/mg  C)], dichloroacetic acid (0.27  (mu)mol/mg  C), and trichloroacetic acid (0.14  (mu)mol/mg  C). This work complements other studies, which focused on algal total organic carbon (DOC and cellular material), and clearly demonstrates the importance of identifying algae-derived sources of DOC in water supplies and removing such DOC in water treatment plants prior to chlorination.