Abstract: This aerobic waste pretreatment process comprises inoculating a milk industry effluent with a mixture of bacteria and yeasts both classes of microorganisms capable of living and growing in symbiosis in the effluent, the population of the bacteria being, in most cases, several times greater than the population of the yeasts, maintaining the temperature and pH of the inoculated effluent between 0.degree. C. and 50.degree. C. and between 1.7 and 9, aerating the effluent while varying, if necessary, the pH at maximum rate of 1.5 pH units per minute and also, if required, modulating the aeration of the inoculated effluent at a maximum rate of 130 micromoles of oxygen per minute. A biomass is obtained which has a good nutritional value suitable for animal feed.

Abstract: A process for the recuperation, in a form usable by Man, of the proteins present in the sullage of the dairy industry. This process is effected in a number of devices successively including a biological pre-neutralizing tank, in which the alcaline sullage is submitted to acidic fermentation and is freed from sand, a neutralizing reactor for a further acidification of this sullage by depositing natural zoogloea over the divided materials which are within the reactor, a flocculating device for coagulation of the proteins in the sullage in the shape of proteinic flakes under controlled pH conditions, and a floatation device in which the proteins are floated by micro-bubbles and gathered by scraping. A novel combined flocculation and floatation adjuvant is described; it increases the isoelectric pH, so as to decrease consumption of added acid and increase the flocculation pH range.