שאלה | Two UF membranes are clogged, the first with negatively charged inorganic colloids and the second with NOM. In both cases, the pH was increased after fouling was detected. (i) For the colloid-fouled membrane, permeate flux increased, while (ii) for the NOM-fouled membrane, the opposite behavior was detected, and permeate flux decreased. The following reasons are suggested. Please select the one that makesthe most sense:

Two UF membranes are clogged, the first with negatively charged inorganic colloids and the second with NOM. In both cases, the pH was increased after fouling was detected. (i) For the colloid-fouled membrane, permeate flux increased, while (ii) for the NOM-fouled membrane, the opposite behavior was detected, and permeate flux decreased. The following reasons are suggested. Please select the one that makesthe most sense:

		(i) The high pH caused the negatively charged colloids to be rejected from the membrane due to the fact that the membrane’s electric double layer had thickened. (ii) The high pH caused the NOM to change conformation, expand, and block the membranes.
		(i) The high pH caused the negatively charged colloids to attach to the membrane due to the fact that the membrane’s electric double layer had become thin. (ii) The high pH caused the NOM to change conformation and block the membranes.
		(i) The high pH caused the negatively charged colloids to be rejected from the membrane due to the fact that the membrane’s electric double layer had thickened. (ii) The high pH caused the NOM to change conformation and detach from the membrane because of their flexibility.

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