Answer:most protozoa (prevalently attached ciliates) can only graze on suspended bacteria and particles; in this way they have a significant effect on the effluent quality.
Explanation:Even though some protozoa (crawling ciliates and other forms) can eat flocculated bacteria, most protozoa (prevalently attached ciliates) can only graze on suspended bacteria and particles; in this way they have a significant effect on the effluent quality.