Try a Hidrostal. They have very good delicate handling properties (good on activated sludges), small footprint, high efficiency & low spares usage.
They also have a very steep Q/H curve, which allows them to cope better than a typical centrifugal pump, when sludge consistency (& thus head...
Hidrostal gas driven pumps have been used in Sydney on this project.
EEKELs the Dutch Hidrostal agent have over 100 similar, mobile units for emergency stormwater & sewage over-pumping. These are strategically placed around cities to give rapid response times