Bacterial regrowth

All water sources may contain natural organic matter, but concentrations (usually measured as dissolved organic carbon, DOC) differ from 0.2 to more than 10 mg L l. NOM is a direct quality problem due to its color and odor, but more important are indirect problems, such as the formation of organic disinfection by-products (DBPs, e. g. M -halomethanes (THMs) due to chlorination), support of bacterial regrowth in the distribution system, disturbances of treatment efficiency in particle separation, elevated requirements for coagulants and oxidants or reductions in the removal of trace organics during adsorption and oxidation, etc. 

Table 1 Fe concentrations, Chi a per cell, P. antarctica cell abundance, particulate organic carbon (POC), particulate organic nitrogen (PON) and dissolved organic carbon (DOC) in the P. antarctica cultures under low Fe (<1 nM Fe, LFe) and Fe amended (FIFe) conditions used for bacterial regrowth experiments...

If these molecules are not toxic they are nevertheless unwanted since amino acids are easily assimilated, and they may be precursors of bacterial regrowth. Also the final chlorination of these molecules leads to the formation of aldehydes and nitriles [ 14, 25 ], which are probably more toxic than the original amino acid. 

Finally, the effectiveness of photocatalysis for disinfection has been further assessed. In particular, the optimization of the treatment and the control of bacterial regrowth have been investigated. ... 

Drikas, M., Christopher, W., Chow, K., and Cook, D. (2003). The impact of recalcitrant organic character on disinfection stability, trihalomethane formation and bacterial regrowth An evaluation of Magnetic Ion Exchange Resin (MIEX) and alum coagulation. J. Water Supply Res. TechnoL Aqua 52(7), 475-487. 

---