The Effect of Larvae of Chironomus Riparius Meigen on the Redox Potentials of Settled Activated Sludge

The introduction of Chironomus riparius larvae to give densities of 12,500 and 50,000/m2in activated sludge, previously settled and consolidated for 6 months, had the following effects: (a)a rise in pH initially at the sludge surface but later extending to all depths, (b)an increase in the depth of the surface layer of sludge where the redox potential is high, (c)increases in the pH value and concentration of ammonia and a decrease in the concentration of oxidized nitrogen in the overlying water.