Development of an environmental decision support system to enhance coagulation in drinking water treatment plants
- Autores: Jordi Suquet
- Directores de la Tesis: Hèctor Monclús Sales (dir. tes.), Lluís Godo-Pla (codir. tes.), Manel Poch Espallargas (tut. tes.)
- Lectura: En la Universitat de Girona ( España ) en 2022
- Idioma: inglés
- Tribunal Calificador de la Tesis: Karina Gibert Oliveras (presid.), M. Dolors Balaguer Condom (secret.), Fernando Valero Cervera (voc.)
- Programa de doctorado: Programa de Doctorado en Ciencia y Tecnología del Agua por la Universidad de Girona
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
Currently, the access to safe drinking water remains to be crucial for mankind development. Due to the geographical context, changes in demography and climate change perspectives, there are regions where water resources are being altered in terms of quantity and quality, compromising future generations availability. Within this context, drinking water treatment plants (DWTPs) are aimed to remove water pollutants through several processes to produce safe drinking water. For DWTPs, one of the main challenges is natural organic matter (NOM), a group of organic compounds which has the capacity to react during the water treatment to generate disinfection by-products (DBPs).
Inside the drinking water treatment train, coagulation is a conventional physicochemical treatment presenting high potential in terms of NOM removal.
From here, the optimisation of coagulation for NOM removal at full-scale level can be achieved based on water quality. DWTPs digitalisation is increasing, providing a number of online measurements which allow to control NOM from the catchment to the final produced waters, including coagulation step.
The main objective of this thesis is the development of enhanced coagulation environmental decision support systems (EDSS) aimed to optimise coagulation for NOM removal at three surface water DWTPs located in the Mediterranean region.
To achieve that, an enhanced coagulation EDSS is developed and a three-level operation is proposed: data acquisition, control and supervision levels (Chapter 4).
The EDSS was designed to propose the optimal values of coagulant dose (Cd) and pH based on raw water characteristics. From this, enhanced coagulation empirical models based on response surface methodology (RSM) were developed to be integrated into the EDSS control level. These models were aimed to remove turbidity, total organic carbon (TOC) and ultraviolet absorbance at 254nm (UV254).
Then, several supervision rules (SRs) were incorporated at the supervision level.
These were designed based on expert knowledge and results obtained from ultrafiltration membranes (UF) experiments, which highlighted UV254 as an important fouling indicator. From that, the final proposed EDSS was designed to achieve 62% of turbidity, 21% of TOC and 25% of UV254 removals during coagulation step.
From the methodology described in Chapter 4, enhanced coagulation models were developed for two DWTPs presenting different types of catchment: river and reservoir (Chapter 5). To evaluate raw waters NOM fluctuations, cluster analysis was performed for both DWTPs identifying baseline and peak NOM scenarios. The enhanced coagulation models were specifically developed for each catchment type and scenario, aimed to remove turbidity, TOC and UV254. Subsequently, models predictors selection and sensitivity analysis allowed to identify the critical factors to achieve enhanced coagulation at each scenario. For both DWTPs, results indicated that Cd is a crucial factor to remove NOM in peak scenarios, while baseline scenarios optimisation require a multiparametric optimisation (considering pH, Cd and Fd).
Models from Chapter 5 were tested with historical data and later integrated in a EDSS control system aimed to minimise trihalomethanes (THMs) using enhanced coagulation (Chapter 6). Results from EDSS application for the historical datasets shown that peak scenarios presented high values of THMs. From here, the developed EDSS proposed a readjustment of Cd which reduced THMs values below the limit in 99.2% of cases.
This thesis describes a methodology that allows to plan, design and develop an enhanced coagulation EDSS for drinking water treatment. To achieve that, empirical enhanced coagulation models were developed and integrated into EDSS control systems. The proposed EDSS were designed to propose the best suitable operational conditions for enhanced coagulation at the three case study DWTPs.
