Amino Acids as Potential Precursors to Odorous Compounds in Tap Water during Spring Runoff Events.

The onset of spring runoff in northern climates and tap water odor events are difficult to predict because common water quality parameters cannot fully explain the intermittent odor events that occurred over past decades. Studies have shown that small polar water-soluble compounds, such as amino acids (AAs), leach first from ice/snowmelt. AAs are known to produce odorous compounds, such as aldehydes and chloroaldimines, upon chlorination. Therefore, we proposed that AAs may serve as markers for small and soluble organics that contribute to the odor of chlorinated tap water. Here, we studied the occurrence of AAs in source water collected at two water treatment plants and the odor profiles of tap water at >300 homes during the 2021 and 2022 spring runoff events. AA concentrations were at baseline levels (<100 ng/L) during the 2021 runoff but much higher (up to 5500 ng/L) in 2022 and associated with an escalation in odor complaints. AA concentrations peaked at the onset of the 2022 spring runoff and corresponded with the strongest reported odor intensities in tap water. We obtained high resolution MS and MS/MS spectra of chloroaldimines and confirmed the formation of chloroaldimines under chlorination of the six AAs detected in source water. The results indicate that AAs signal the onset of spring runoff and represent small polar water-soluble compounds that may contribute to tap water odor problems.

Removal of Cryptosporidium surrogates in drinking water direct filtration.

Pilot-scale direct filtration challenge experiments were conducted to determine the impact of chemical pretreatment and filter design on the removal of Cryptosporidium surrogates dosed into the filter influent water at low temperatures (Average 0.5 °C). Copolymers-modified microspheres were identified as representative Cryptosporidium oocysts surrogates based on our previous findings and were used to evaluate the oocysts filtration removal at this pilot-scale study. The operational parameters examined included coagulant type (aluminum sulfate (alum) versus polyaluminium chloride (PACl)), filter aid polymer type (polyamine Magnafloc® LT-7981 versus poly(Dimethyl Diallyl Ammonium Chloride) (polyDADMAC) Magnafloc® LT-7995) and dose (0.5 versus 2.0 mg/L), and filter configuration (regular versus deep bed filters). The study found that higher Cryptosporidium surrogate removal was associated with higher polymer dose (2 mg/L) of polyDADMAC polymer and the deep bed filter configuration. The difference in surrogate removal between PACl and alum was no significant at cold temperature conditions tested. The deep bed filters were associated with higher surrogate removal, while exhibiting lower rates of flow reduction and longer filter run time. This work emphasizes the importance of optimizing chemical pretreatment and filter configuration for removing surrogates of Cryptosporidium oocysts in cold-water conditions in granular media water filtration processes. This pilot-scale study also demonstrated the exceed 2.5-log removal of Cryptosporidium surrogates (required from Guideline for Canadian Drinking Water Quality) can be achieved in the direct filtration during Edmonton cold-water condition when the pretreatment processes are optimized using 0.454 mg/L of alum as Al with addition of 0.5 mg/L poly DADMAC.