Disinfection is an essential process for both potable water and wastewater treatment plants. However, DBPs like trihalomethanes (THMs), haloacetonitriles (HANs), and nitrosamines are formed when organic matter precursors react with the disinfectants like chlorine, chloramine, and ozone. Formation of DBPs is strongly associated with the type of water source, type of disinfectant, and natural organic matter concentration, which can have seasonal variation.

In this study, water samples were collected from 20 different intra-watershed locations, which included urban runoff (with and without the influence of unsheltered homeless populations), wastewater effluent discharges within urban channels, and a large, terminal reservoir that serves as the local drinking water source. Samples were collected on dry and rainy days. DBPs formation potential (FP) tests were conducted at consistent pH, contact time, and temperature. THMs, nitrosamines, and HANs were analyzed by gas chromatography-mass spectrometry (GC-MS).

The FP tests performed on these water samples revealed that chlorine formed the highest THM concentrations while THM concentrations were low for the ozone FP test as expected. Chloramine produced the greatest HAN concentrations, with dichloroacetonitrile forming the highest concentration and monoiodoacetonitrile forming the lowest concentration. In relation to location, more DBPs were formed at the non-wastewater-impacted runoff sites as compared to the wastewater effluent discharge sites. In respect to TOC levels, rain event samples for all locations had higher TOC concentrations compared to dry sampling days. Similarly, rain event samples showed increased DBP formation; a significant amount of precursors for THMs were found in runoffs from wastewater effluent discharges and unsheltered homeless locations (concentration of total THMs for chlorine FP test was >200 µg/L). Therefore, urban runoff waters, especially those impacted by unsheltered homeless populations, should be considered as potential sources of DBP precursors to drinking water source waters, and runoff water is prone to seasonal variation.

Access the Conference Proceedings Paper on ASCE Library 

Disinfection is an essential process for both potable water and wastewater treatment plants. However, DBPs like trihalomethanes (THMs), haloacetonitriles (HANs), and nitrosamines are formed when organic matter precursors react with the disinfectants like chlorine, chloramine, and ozone. Formation of DBPs is strongly associated with the type of water source, type of disinfectant, and natural organic matter concentration, which can have seasonal variation.

In this study, water samples were collected from 20 different intra-watershed locations, which included urban runoff (with and without the influence of unsheltered homeless populations), wastewater effluent discharges within urban channels, and a large, terminal reservoir that serves as the local drinking water source. Samples were collected on dry and rainy days. DBPs formation potential (FP) tests were conducted at consistent pH, contact time, and temperature. THMs, nitrosamines, and HANs were analyzed by gas chromatography-mass spectrometry (GC-MS).

The FP tests performed on these water samples revealed that chlorine formed the highest THM concentrations while THM concentrations were low for the ozone FP test as expected. Chloramine produced the greatest HAN concentrations, with dichloroacetonitrile forming the highest concentration and monoiodoacetonitrile forming the lowest concentration. In relation to location, more DBPs were formed at the non-wastewater-impacted runoff sites as compared to the wastewater effluent discharge sites. In respect to TOC levels, rain event samples for all locations had higher TOC concentrations compared to dry sampling days. Similarly, rain event samples showed increased DBP formation; a significant amount of precursors for THMs were found in runoffs from wastewater effluent discharges and unsheltered homeless locations (concentration of total THMs for chlorine FP test was >200 µg/L). Therefore, urban runoff waters, especially those impacted by unsheltered homeless populations, should be considered as potential sources of DBP precursors to drinking water source waters, and runoff water is prone to seasonal variation.

**[Access the Conference Proceedings Paper on ASCE Library](https://doi.org/10.1061/9780784483466.058)** 

Spatial and Seasonal Variations of Disinfection Byproduct (DBP) Precursors in Relation With Total Organic Carbon (TOC)

Created in 1999, the Environmental & Water Resources Institute (EWRI) is the recognized leader within ASCE for the integration of technical expertise and public policy in the planning, design, construction, and operation of environmentally sound and sustainable infrastructure impacting air, land and water resources.

[Paper Proceedings](https://doi.org/10.1061/9780784483466)

Conference DOI: https://doi.org/10.26226/m.6329c39b68fb0e00131f77d2