To reveal the character and quantitative aspect of interrelations be- 

 tween bacteria and protozoa in the process of destroying organic matter, it 

 is necessary to use mathematic models. We used models similar to Canale's 

 (1970) models, in which the dependences between specific growth rates and 

 feeding of organisms and the concentration of their food was linear. Such 

 a linearization has appeared to be quite acceptable for test conditions 

 allowing only a small change interval in the component values. 



For the system—organic matter-bacteria: 



*j| = D(S r S) - kjSH 



^= k 2 SH - DH 



> (D 



For the system—organic matter-bacteria-infusoria 



dS 

 dt 



dH 

 dt 



dP 

 dt 



D(Sj-S) - kjSH - k 3 SP 



= k 2 SH - DH - k,HP 



= k 5 HP + k fi SP - DP 



> (2) 



where S - is the concentration of organic matter in the reactor 

 Sj - the same, in the inflowing medium 



H - concentration of bacteria in dry matter 



P - the same, for protozoa 



D - dilution rate 



t - time 



k.j - coefficients of proportinality. 



For the system—organic matter-bacteria-zoof lagel lates, a model was con- 

 structed taking into account the possibility of feeding the zoof lagel lates 

 with the dissolved organic matter (DOM) (Goryacheva, 1975): 



135 



