Ceramic nanofiltration for direct filtration of municipal sewage

Worldwide population growth, water scarcity, and climate change contribute to an urgent need for alternative water sources for irrigation water, industry water, and, in some countries even, drinking water. The implementation of municipal sewage reclamation is an upcoming trend in water treatment. The use of municipal sewage has the advantage of keeping the water circles small. Moreover, more is to gain from municipal sewage: nutrients and energy are abundantly present in this water and could potentially be recovered too.
The purpose of this research was to study the potential of the application of ceramic nanofiltration for treatment of municipal sewage. Ceramic nanofiltration membranes were chosen because of their high mechanical strength and high chemical and thermal resistance. These membranes are expected not to be damaged by high pressures, temperatures, concentration of chemicals, which enables vigorous chemical cleaning of the membranes, and they are prone to less irreversible fouling compare to polymeric nanofiltration NF.
This research was divided into four parts. First, a preliminary pilot study showed that ceramic nanofiltration membranes have potential for direct treatment of municipal sewage as pretreatment for reverse osmosis. Second, the quality and robustness was thoroughly researched and was lower than expected. Third, the phosphate retention during ceramic NF was notable effected by pH, multivalent counter ions, and a fouling layer on the membrane surface. Fourth, several fouling control method were tested using ceramic nanofiltration: the highest flux was maintain when applying reaction based precoat, resulting in the net highest water production.