Human rights don’t favour any one service delivery model over another. They demand that the state sets up a system within which service delivery can take place – by state owned or private service providers.
For any such system, regulation and enforcement is crucial to ensure accountability: To what standards do service providers have to work? Who is responsible for what? Are standards really enforced (against any type of service provider)?
“The private sector” also means many different things: Large private sector service providers are quite rare, but small scale private sector providers are almost always involved in service delivery, especially in rural areas: Drillers, builders, sludge collectors, mechanics, etc.
Another example that shows the importance of regulation and enforcement by the state: Renters. The landlord is usually responsible for building the WASH infrastructure INTO the house. This needs building regulations that need to be checked and enforced. And clear roles and responsibilities if something inside the house breaks down: Is it the responsibility of the tenant or the landlord?
In case of private sector actors violating rights (e.g. extractives, beverage companies): The state must protect people’s human rights from violations by private sector actors. Again through laws, regulations and enforcement. For instance, BEFORE any private sector actor starts anything that might impact people’s ability to enjoy services, the impact should be carefully checked, people should have the ability to participate/be consulted, etc. and if the enjoyment of their rights deteriorates (the aquifer runs dry, sources are polluted), they should have a way to seek redress.