Over 1.7 billion students around the world have had their education disrupted by the spread of the Coronavirus disease worldwide. Schools and universities have not faced this level of disruption since World War II. The COVID-19 pandemic presented a colossal challenge for teachers to urgently and massively adapt all their classes to distance learning in order to maintain educational continuity with the same quality. Even if some teachers and certain classes were ready to face the situation, a large majority had to adapt their teaching and learning in a very short time without training, with insufficient bandwidth, and with little preparation. This unexpected and rapid transition to online learning has led to a multiplication of teachers' strategies for distance learning in lectures, tutorials, project groups, lab works, and assessments. The purpose of this paper is to present the feedback from students and teachers who participated in the lockdown semester of two different groups of a 5-year program in Chemistry, Environment and Chemical Engineering (100 students) at INSA Toulouse (France). The analysis has highlighted some great successes and some failures in the solutions proposed. Consequently, some guidelines can be given to help us all to learn the lessons of such a singular experience in order to face the unexpected future with more knowledge and more successful distance learning. Teachers have shown very strong resilience during this crisis, at the cost of significant personal commitment. They admit that they have learned more about distance education in two months than in the last 10 years.

This paper presents experiments showing the existence of a critical filtered volume (CFV) when operating colloid dead-end filtration. The CFV is here defined as the filtered volume below which there is no irreversible (with respect to a break in the filtration) fouling on the membrane surface: it has thus the same meaning as cross-flow critical flux but applied to a dead-end process. The existence of the CFV is demonstrated when filtering stable latex or clay suspensions in constant-flux filtration experiments with alternating rinses: in contradiction to the current view, an irreversible deposit is not formed as soon as dead-end filtration begins. This critical filtered volume is shown to be dependent on the suspension stability and to be fully linked to the permeate flux: for permeate fluxes of 80 and 110 l h −1 m −2 the CFV is, respectively, 82 and 65 l m −2 for latex particles. Analyses of results are made by depicting the transition between concentration polarisation and deposit formation considering a critical osmotic pressure, which appears to be a characteristic of the fouling potential of a suspension. The results are discussed in the light of how this concept could lead to an interesting way to control and develop a strategy to operate filtration in dead-end mode.