In Hong Kong, sea water is now used for a parallel sanitation system. But, since building a parallel system of distribution for sea water would be too expensive for most older cities, brine may be pumped into existing fresh water systems. However, a likely danger of such a choice would be contamination of fresh groundwater supplies by exfiltration from leaking sewerage. Further, current infrastructure for transporting fresh groundwater to people for drinking, cooking, and washing would be rendered unusable. Sewage leakage into water supplies and into groundwater is increasingly common worldwide.
Municipalities are uncertain where financing for rehabilitation of the pipes can be found.
If the situation is desperate for OECD cities, the problem of funding the rehabilitation of leaky water supply and sewer systems is orders of magnitude worse for LDC cities, which by definition have less money to spend and where human populations are already larger and growing faster. That is, it cannot solve the multiple problems caused by this form of water pollution. As a system, it cannot clean the water we have chosen to pollute without introducing more complex and environmentally unsustainable effects. The inevitable products of this system are first more or less degraded water, and second more or less toxic sludge. Each stage only leads in its turn to more unsolvable problems as the primary problem is merely moved from one place to another, and from one form to another.