We made petcoke work as water & solids filter at COP/Venco Moundsville Calciner – long before this Syncrude guy thought about using petcoke to clean up outgoing effluent water!
The guys at the plant used old railcar (took off wheels, put in baffle system & used waste fines as filter to catch storage run-off water which had some coke particles & oil films from volatiles.
We dumped the railcar fines often & sold them as fuel and added fresh fines bake in. Water going into river was cleaner than the river water.
I’ve mentioned to lots of people over years & even posted it on coking.com.