Contractors have been brought in to clear rubbish as bin workers in Birmingham start industrial action.
Unite union workers are working to rule, claiming they were denied a payment which was given to GMB members, who did not strike in 2017.
Unite accused the city council of "blacklisting" strikers, which the authority denied.
The council said residents should leave bins out as usual adding it was working with Unite to resolve the dispute.
The present action means Unite members are only working contracted hours and return to base for breaks.
A council spokeswoman said the contractors would "clear a backlog of collections missed during Christmas week".
A Unite spokesman said the action would continue until a deal was reached or new ballot held.
"We are in ongoing discussions to see if a resolution can be reached," he said.
"The council has been made aware that there must be parity in the workforce and that Unite cannot stand by and watch their collective undermined by secret payments made to those who did not go on strike."
About 300 refuse collectors voted 97% in favour of action short of a strike.
GMB had said suggestions its members received extra payments for not taking strike action would be "inaccurate and misleading".
The 2017 strike lasted for three months and saw uncollected waste pile up on city streets and the then-council leader forced out.
A new shift pattern was brought in for workers earlier this year as part of an agreement to end it.
The council added: "Our top priority as we work with Unite to resolve this dispute is to keep the city's streets clean, and part of our contingency plan is to bring in external support to help us to do that."