Subtooting something that said anarchists don't know how to clean a city's sewers because an online anarcho argued the answer to “who will clean the sewers” was that sewers would be abolished in favor of community-scaled composting and plumbing. I don't actually disagree. Modern sewage systems are environmentally destructive and takes a convoluted industrial process to detoxify sewage.
Liberals and state socialists aren't ready for a conversation about creating ways of living that compliment rather than contradict the natural world. Of course hard questions like “how will we manage sewage” need to be answered, but we mustn't shy away if the answers are scary — that current ways of living may not or even could not exist in a truly liberated society.