I just dumped the contents in the toilet and rinsed it out in the laundry sink in the washroom. I figure people were potentially washing diapers in there so as long as I rinsed the sink out, it was fine.
Aside: This place used to have a beautiful old stone laundry sink. I still remember my Mom bathing me in that sink, then dressing me in footy pajamas and rubber boots, which were the only thing that fit over the feet. 39 years later, there are still people who remember me tromping across the campsite in that get up, complete with pigtails.