 Most of South America, Sub-Saharan Africa, Southern China and India will face water supply shortages by 2025; for these latter regions the causes of scarcity will be economic constraints to developing safe drinking water, as well as excessive population growth.Water supply and sanitation require a huge amount of capital investment in infrastructure such as pipe networks, pumping stations and water treatment works.It is estimated that Organisation for Economic Co-operation and Development (OECD) nations need to invest at least US$200 billion per year to replace aging water infrastructure to guarantee supply, reduce leakage rates and protect water quality.