Investigation of the Effect of Treated Wastewater on River Temperature and pH


  • Simran Dhaliwal
  • Harsajjan Dhillon
  • Parmvir Shergill
  • Simran Shergill


The Squamish Wastewater Treatment Plant (WWTP) utilizes bacteria to biodegrade
organic matter and sulphur dioxide for the process of dechlorination, which increase the
temperature and reduce the pH of the treated water, respectively. This process can modify the
temperature and pH levels of effluent water flowing back into rivers, resulting in detrimental
consequences for keystone species in B.C., particularly salmon. This study aims to compare
temperature and pH both upstream and downstream of Squamish’s WWTP to identify the impact
of the treatment process on river properties. We hypothesized that the treated wastewater released
from the outflow site would (1) lower river pH and (2) increase river temperature. Using a pH
probe and a thermometer, pH levels and temperature were measured 100 feet upstream (n=5) and
100 feet downstream of the WWTP outflow site (n=5). Collecting data from two separate trials, a
two-sample t-test indicated that pH levels upstream and downstream were significantly different
in both trial 1 (p = 0.0363) and trial 2 (p = 0.0000343). Furthermore, the two-sample t-test
conducted on the temperature data indicated that the mean temperature difference between the
upstream and downstream sites was statistically insignificant in both trial 1 (p = 0.2826) and trial
2 (p = 0.2844). In conclusion, our findings supported our pH hypothesis and failed to support our
temperature hypothesis. This observed alteration of river pH can have adverse implications on
salmon survival at all stages of life.