This company is still advertising its tanker services in 2020.

https://dotless.ae/how-does-dubai-manage-its-sewage-water/

From 2016 so Dubai may have had a working sewage system for a year, so I could be wrong.

> Dubai: The emirate of Dubai will get a new deep tunnel sewerage system costing Dh12.5 billion in the next five years to replace more than 121 sewage pumping stations.

Pumping station meaning tankers transport the waste away.

https://gulfnews.com/uae/government/dubai-to-get-a-new-sewag...