Skip to main content

Trinity College Dublin, The University of Dublin

Trinity Menu Trinity Search

You are here People

Yunhong Shi

PhD Researcher
Dept. of Civil, Structural & Environmental Engineering



Investigation into the cause, impacts and measurement to deal with algal blooms in Vartry Reservoirs

Keywords: diatom, algal bloom, reservoirs, drinking water, nitrogen, phosphorus.

Diatom algal blooms in water supply sources can cause many problems in the drinking water treatment process. Vartry Reservoir is an important drinking water source in Ireland. Diatom algal blooms have caused problems in the sand filters in the Roundwood water treatment plant since 2007 (except 2010). In 2013 and 2014, the situation worsened and serious spring diatom algal blooms occurred, with peak concentrations of diatom algal up to 1750 and 2457 counts/ml, respectively, resulting in serious clogging of the slow sand filters and a reduction in treatment capacity from 75 million litres to 40 million litres per day and consequently water shortages in the North Wicklow and South Dublin area two years in a row.


In addition, diatom algal blooms might also contribute to the high THMs in the Vartry Water Supply Scheme. Therefore, the aim of the proposed study is to investigate the cause of the diatom algal blooms in Vartry Reservoir and to identify potential measures to deal with the impact of algal blooms in Roundwood water treatment plants. This proposed project is important not only for the Vartry Water Supply Scheme but also for water supplies nationwide, as more than 70 mesotrophic lakes are used as water supply sources in Ireland.

The objectives and targets of this proposed study are to:

  • Identify the main sources and pathways of nutrients (including Si, a nutrient for diatom growth) entering the Vartry Reservoir by collecting historical dataset and carrying out monitoring programme;
  • Identify factors that actually control diatom algal populations in the reservoir by investigating diatoms and its interaction with environmental factors such as nutrient levels, hydrodynamics, light and wind;
  • Recommend a set of measures to reduce the inputs of nutrients;
  • Select and calibrate models for the prediction of algal blooms to allow future blooms to be predicted at an earlier stage;
  • Investigate the potential mitigation measures to (1) prevent diatom algal blooms and (2) to reduce the impact of the blooms on water supplies when they do occur for the Vartry Reservoir, as well as other mesotrophic lakes which are used as water supply sources in Ireland.



Project Supervisor: Assistant Prof. Liwen Xiao