Online THM Monitoring System Supports Cutting Edge Innovation and Research

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Online THM Monitoring System Supports Cutting Edge Innovation and Research

The Bilbao Bizkaia Advanced Water Treatment Centre (CATABB) in Etxebarri, Bizkaia, Spain, is an open platform for innovation and research in water treatment that was designed and built by the Bilbao Bizkaia Water Consortium (BBWC) in 2018. The CATABB plant, with a treatment capacity of 10 m3/h, is an advanced and versatile drinking water facility that is equipped with different technologies to evaluate suitable approaches for the purification of water of different characteristics and origins (the Nervión river, the Zadorra reservoirs or a mix from both).

The treatment train at the facility includes four different pre-oxidation processes (chlorine, chlorine dioxide, ozone and potassium permanganate), followed by coagulation/flocculation and sand filtration. Subsequently, water may be treated with ozone, a combination of ozone and hydrogen peroxide, a UV light process, or it may be directly filtered using a granulated activated carbon (GAC) filter. Two GAC filters are placed in parallel, each using a different type of GAC media so that their water filtration efficiency under the same or different operational conditions can be compared. Following filtration, water is disinfected with chlorine.

Studying Desorption Processes of THMs
The CATABB plant aims to promote knowledge sharing of innovative technologies and cooperation across public and private partners. During the last three years several research studies have been carried out at the facility, one of which is “Adsorption and Desorption Processes of Trihalomethanes on Different Granulated Activated Carbon (GAC) Filters.”

Online THM Monitoring System Supports Cutting Edge Innovation and Research
at the Bilbao Bizkaia Advanced Water Treatment Centre

This project gives real insight into the desorption processes of trihalomethanes (THMs) produced when characteristics of the feed water or the treatment process are modified at a drinking water plant using GAC.
The main highlight of this two-year study was to show full-scale, real-world data on the adsorption and desorption processes of different GAC compounds under various operational conditions. The demonstration project studied the saturation of GAC filters and any changes to their adsorption capacity because of varying the water source, altering any water characteristics, and changing the oxidation agent. Results from the study were presented at the IWA World Water Congress and Exhibition in September 2022.

The desorption process of harmful organic compounds such as THMs can be a cause of great concern to drinking water plants, especially if the desorption process is fast and high. To aid CATABB in their study to better understand the adsorption and desorption process of their GAC filters, an Aqua Metrology Systems online THM-100™ analyzer was installed at the facility to deliver fast, accurate and reliable data on THM levels. Despite fluctuations in THM values, treated water in the CATABB plant was always below the regulatory limit of 100 ppb (European Directive 2020/2184), even when the nmost depleted GAC was tested.