Why are municipal wastewater treatment plants abandoned in Mexico? When a more money policy approach is not enough

The abandonment or closure of wastewater treatment plants is a potential problem in sanitation policies, where municipalities must decide which type of plant should build in their territory. We used an interaction effects model to test the effect of financial self-sufficiency in the operation of Mexican treatment plants in the national sanitation policy periods: the more money policy approach and the more planning policy approach. Our results show that during the more planning policy approach, the wastewater treatment plants' effectiveness increases more than the more money policy approach period, which is more vital in plants with low operating costs. Municipal financial self-sufficiency positively affects wastewater treatment plants' effectiveness more substantially in plants with high operating costs. Policy implications of these findings aim to be careful with the more money policy approach to developing wastewater infrastructure since municipalities require proper planning for the particular conditions of each site. The Mexican case shows how combining municipal financial insufficiency and centralization of planning in the national government, as is common in the countries of the Global South, affects the probability of plant survivorship. Furthermore, the effect of this combination grows when national governments increase their budgets to invest.