There is a major machlokes rishonim whether a mikva that is made of drawn water would be a p'sul d'oraysa or only d'rabonon. In my sefer, Mayim Rabim (page 37), I elaborated about this issue and presented many shitos in the rishonim. The Rambam holds that she'uvin (drawn water), even an entire mikva of drawn water, would only be passul d'rabonon. The Rash disagrees because a mikva that is man made - הוייתו ע"י אדם, would be pasul m'doraysa, but not because it is "drawn" rather because it is made through keilim that are susceptible to tu'mah. According to the Rash, when the Rabbonon make a gezeira that 3 Lug of drawn water passul the mikva, they would also include in this gezeira any 3 lug of water that is brought to the mikva by means of something that is susceptible to tu'mah. Since the source of the problem with drawn water is tu'mah, it makes no sense to make a distinciton. However, the Rashabam and Rabbeinu Tam (baba basra 66a) hold that a mikva comprised of mostly drawn water would be passul m'doraysa. This is the prevalent opinion. The Rabbonon are then gozer that even 3 lug of drawn water invalidates the mikva. But, there is even an opinion (rosh in the namne of Rabbeinu Tam) that the p'sul of 3 lug is halacha l'moshe misinai, meaning that it is d'oraysa.
As we see from our gemara, the concept of 3 lug of drawn water passuling the mikva (prior to the mikva having 40 se'ah), only applies to water. But, 3 lug of any other liquid such as wine, even white wine wouldn't passul the mikva (the only way that wine would passul the mikva is by changing the color). Based on this, there is a very interesting question, when one adds white wine to a mikva that is less than 40 se'ah, and the wine completes the shiur of 40 se'ah, would the mikva be valid? It seems that although wine doesn't ruin a mikva, it also can't create a mikva. Meaning, that without a full 40 se'ah of water, the mikva would not be kasher.
We pasken like the tana kama of the braisa based on rav papa's question, that in order to passul the mikva we would require a full 3 lug of water, and it must have the appearance of water. If either it has a kurtav less than 3 actual lug of water, or it looks like wine, it wouldn't passul the mikvah. Based on this, the Aruch Hashulchan raises a question: What if 3 lug of drawn water got mixed with 4 lug of white wine, and the mixture then fell into the mikva - do we say that it passuls since there is 3 lug of actual water and it has the appearance of water, or do we say that the water is batul in the wine and it is as if wine is falling in so it wouldn't passul (so long as you add enough actual rain water afterward to be mashlim the shiur of the mikva)?