Computational flow cytometry of planktonic populations for the evaluation of microbiological-control programs in district cooling plants

Abstract

Biofouling poses a serious concern for the district cooling (Dc) industry. current industry practises for monitoring biofouling continue to rely on culture-based methods for microbial enumeration, which are ultimately flawed. Computational flow cytometric (cFCM) analyses, which offer enhanced reproducibility and streamlined analytics versus conventional flow cytometry were applied to samples taken from 3 sites in each of 3 plants over a 5-week sampling program. We asked whether the application of cfcM to monitoring planktonic community dynamics in Dc plants could be able to provide sufficient information to enhance microbiological-control strategies at site and inform about plant performance impacts. the use of cfcM enabled the evaluation of biocide dosing, deep cleaning treatment efficiencies and routes of microbial ingress into the studied systems. Additionally, inherent risks arising from the reintroduction of microbiological communities into recently cleaned Wct basins from contaminated cooling waters were identified. However, short-term dynamics did not relate with plant performance metrics. In summary, the insights offered by this approach can inform on plant status, enable evaluations of microbial loads during biofouling mitigation programs and, ultimately, enhance industry management of the biofouling process. Hot urban climates requires extensive cooling to provide habitable indoor environments and high demand in electricity and water use. Centralized production and distribution of cooling waters from district cooling plants (DCPs) is the preferred means of providing cooling waters for industrial, commercial and residential use as it is generally more economical than conventional on-site air-based cooling. The current annual energy demand for cooling accounts for 10% of global electricity use and is expected to triple by 2050, largely due to population expansions in developing hot-climate countries, including the Middle East 1. Accordingly, the Gulf Cooperation Council (GCC) has seen a rapid expansion in district cooling facilities to meet airconditioning requirements which are the largest such requirements in the world (in excess of 25,000,000 refrigeration tons (RT) 2). Indeed, the peak consumption in the United Arab Emirates (UAE) is second only to Saudi Arabia in the GCC with the majority of electricity loads (~ 70%) being required for cooling 3. Furthermore, peak cooling demands are forecast to reach 100 M RT in the GCC region by 2030 4. Given the continued expansion of the global population, climate change and lack of alternatives for cooling in high-density urban areas, we can expect a continued reliance on DCPs for the foreseeable future. It is therefore essential that these cooling facilities are operating as efficiently and sustainably as possible in order to meet the demand for cooling, whilst mitigating environmental impacts. District cooling systems are composed of four principle components: a make-up water (MUW) supply line, a centralized Cooling Plant, a chilled water supply network and th...