Mathieu Lapointe

• P. Eng., Ph.D.
• Professor at École de Technologie Supérieure

Ballasted flocculation is widely used in the water industry for drinking water, municipal wastewater, storm water and industrial water treatment. This gravity-based physicochemical separation process involves the injection of a ballasting agent, typically microsand, to increase the floc density and size. However, the physical characteristics of the...

Polyacrylamide polymers (PAM) are one of the most common water treatment chemicals used in clarification processes. Concerns have been raised with regards to the aquatic and human toxicity of acrylamide monomer. Greener polymers, produced using potato starch, were investigated at labscale as a potential non-toxic alternative to the use of PAM withi...

Increasing demand for water poses a major challenge to the water treatment industry. To maintain their floc removal efficiency, water treatment plants are expected to require larger separation units and use more chemicals, namely, coagulants and flocculants. Conventional physicochemical treatments produce flocs that are limited in size, which limit...

Due to growing concerns of plastic pollution release into water bodies, it is imperative to understand and assess the removal of nanoplastics and microplastics during wastewater treatment processes. Although earlier studies have shown high removal of plastic contaminants during coagulation, flocculation and settling, a limited number of experiments...

Fiber-based materials have emerged as a promising option to increase the efficiency of water treatment plants while reducing their environmental impacts, notably by reducing the use of unsustainable chemicals and the size of the settling tank. Cellulose fiber-based super-bridging agents are sustainable, reusable, and versatile materials that consid...

In this work, we probed the changes to some physicochemical properties of polystyrene microplastics generated from a disposable cup as a result of UV-weathering, using a range of spectroscopy, microscopy, and profilometry techniques. Thereafter, we aimed to understand how these physicochemical changes affect the microplastic transport potential and...

The water treatment industry relies heavily on coagulation and flocculation processes. This technology requires large amounts of chemicals and large settling tanks for floc separation. The flocs formed during conventional treatment are small (< 100 µm), which limit their removal by gravitational separation. To improve floc separation, fiber-based s...

The anisotropic nature of 'graphenic' nanosheets enables them to form stable three-dimensional porous materials. The use of these porous structures has been explored in several applications including electronics and batteries, environmental remediation, energy storage, sensors, catalysis, tissue engineering, and many more. As method of fabrication...

Single-use face masks can release microfibres upon exposure to environmental conditions. This study investigates the number of microfibres released in the presence and absence of UV irradiation and mechanical friction and the removal of the released microfibres in a simulated conventional wastewater treatment process. UV exposure results in a four-...

To deal with issues of process sustainability, cost, and efficiency, we developed materials reengineered from fibers to serve as super-bridging agents, adsorbents, and ballast media. These sustainable fiber-based materials considerably increased the floc size (~6,630 µm) compared to conventional physicochemical treatment using a coagulant and a flo...

Most cities lack holistic monitoring and green infrastructure to mitigate pollution in urban runoff. We call for systematic characterization of runoff and more widespread treatment to protect biodiversity and human health. This challenge requires data-driven, adapted, low-cost and sustainable solutions for dense urban centres.

To deal with issues of process sustainability, cost, and efficiency, we developed materials reengineered from fibers to serve as super-bridging agents, adsorbents, and ballast media. These sustainable fiber-based materials considerably increased the floc size (~6630 µm) compared to conventional physicochemical treatment using a coagulant and a floc...

To deal with issues of process sustainability, cost, and efficiency, we developed materials reengineered from fibers to serve as super-bridging agents, adsorbents, and ballast media. These sustainable fiber-based materials considerably increased the floc size (~6630 µm) compared to conventional physicochemical treatment using a coagulant and a floc...

Aggregation combined with gravitational separation is the most commonly used method to treat water globally, but it carries a significant economic and environmental burden as the chemicals used in the process (e.g., coagulants) generate ~8 million tons of metal-based sludge waste annually. To simultaneously deal with the issues of process sustainab...

Aggregation combined with gravitational separation is the most commonly used method to treat water globally, but it carries a significant economic and environmental burden as the chemicals used in the process (e.g., coagulants) generate ~8 million tons of metal-based sludge waste annually. To simultaneously deal with the issues of process sustainab...

Large amounts of expensive single-use and metal-based coagulants and synthetic flocculants are employed and lost in settled sludge during water treatment. In this work, cellulose fibers were grafted with iron (hydr)oxides and introduced as a dispersed suspension during coagulation/flocculation to simultaneously act as a super-bridging agent and ads...

Aggregation combined with gravitational separation is the most commonly used method to treat water globally, but it carries a significant economic and environmental burden as the chemicals used in the process (e.g., coagulants) generate ~8 million tons of metal-based sludge waste annually. To simultaneously deal with the issues of process sustainab...

Aggregation combined with gravitational separation is the most commonly used method to treat water globally, but it carries a significant economic and environmental burden as the chemicals used in the process (e.g., coagulants) generate ~8 million tons of metal-based sludge waste annually. To simultaneously deal with the issues of process sustainab...

To date, most studies of microplastics have been carried out with pristine particles. However, most plastics in the environment will be aged to some extent; hence, understanding the effects of weathering and accurately mimicking weathering processes are crucial. By using microplastics that lack environmental relevance, we are unable to fully assess...

As some water utilities are facing increasing concentrations of natural organic matter (NOM) in source water, it has been observed that some of this organic content is refractory to conventional coagulation treatment with alum and ferric sulfate. However, prehydrolyzed coagulants containing polymeric and/or cationic aluminum species such as Al2, Al...

The efficacy of plastic particle removal by municipal water treatment plants is currently uncertain, and the mechanisms involved in microplastics (MPs) coagulation and flocculation have only been superficially investigated. The removal of pristine versus weathered plastic debris, and the impact of plastic particle size on removal remain largely une...

Flocculation and settling performance (kinetic, robustness, upflow velocity, and overall solids removal) have been significantly improved over the past forty years due to the development of very high molecular weight polymers. Intrinsic flocculant characteristics such as the molecular weight, charge density, and spatial molecular configuration are...

Synthetic polymers, mostly polyacrylamides (PAMs), are frequently used in the water industry to improve the performance of clarification. However, synthetic polymers may increase headloss in granular media filters, biodegrade slowly, and are potentially toxic. Alternatively, bio-sourced starch-based polymers may eliminate the drawbacks of synthetic...

Ballasted flocculation, a process consisting in injecting micron-sized granular media to increase the specific gravity and size of flocs, is being increasingly used in the water treatment industry owing to its potential to achieve very high superficial design velocities. This offers the advantages of a more compact process (i.e., smaller footprint)...

Conventional clarification processes imply specific facility footprints that translate into important capital costs. Ballasted flocculation, consisting of injecting ballast medium to increase floc specific gravity and size, is being increasingly used in the water industry owing to its potential for design with very high superficial velocities. Howe...

Most current commercial applications of ballasted flocculation use silica sand to increase floc size and density. Other ballast media with different specific gravity may offer advantages such as increased applicable superficial velocity or increased particulate matter removal. This study assessed the relative effect of five ballast media on ballast...

Organic polyelectrolytes such as polyacrylamide (PAM) are commonly used in the water industry to improve flocculation. However, potential adverse health effects may arise from the use of PAM owing to the presence of trace acrylamide monomers in commercial products. Hence, there is growing interest in replacing synthetic polyelectrolytes with natura...

GENERAL OBJECTIVE: evaluate the performances of starch-based polymers for ballasted flocculation under a challenging temperature condition (1˚C).