Design of fine-bubble aeration systems for municipal WWTPs with high sea salt concentrations

The impact of sea salt on the aeration coefficient k(L)a of fine-bubble aeration systems was investigated in clean water and in a model substance for simulating activated sludge. The investigations were carried out at laboratory and pilot scale. Sea salt was dosed in the form of artificial seawater, real seawater or simplified, by adding NaCl. The investigated media showed an increase of k(L)a with rising sea salt concentrations up to 10 g/L. The ratio between k(L)a and sea salt concentration is impaired by the air flow rate and the type of applied diffusers. Literature data show that the favourable effect of sea salt on k(L)a can also be found in the activated sludge of conventional municipal wastewater treatment plants. The results of this study allow the derivation of salt correction equations to be used in the design of fine-bubble aeration systems for taking into account the favourable impact of sea salt on k(L)a. By that means, a more precise design of respective systems will be enabled.