Minimum public health, safety, and welfare standards are an important, legitimate, and rational function of government.  Governmental oversight is normally implemented through setting standards, permitting, and compliance requirements.  The on-site waste treatment industry has been the exception in many States, where a governmental agency sets the standards and then tries to perform all the technical evaluations, design, layouts, inspections, and compliance with varying success.  Typically a governmental agency will not assume liability or responsibility for their works when failures occur or insubordinate works are performed, which leaves the public in a precarious position without a legal recourse due to State sovereignty, but the public is still required to comply with minimum health, safety, and welfare standards set by the same State agency.

Privatizing the on-site waste treatment industry with trained, competent, responsible, and legally liable professionals is a rational way to proceed.  This would be the same for any other professional works with as much or greater liability, such as home building, bridge / highway construction, chemical applications, and etc.  

There will always be hardship situations and government typically handles this through public assistance funding for services.  Many professionals also do pro-bono work which can be recouped as a charitable contribution when recognized by governing tax codes.