Two-and-a-half billion people worldwide have no access to safe, durable sanitation systems. Brian Arbogast, director of the water, sanitation and hygiene programme at the Bill & Melinda Gates Foundation, tells SciDev.Net how innovative toilet technologies and business models could help fix this — and help communities cope with the devastation of climate change.How does climate change impact sanitation?With sea levels rising, you have flooding that causes huge health problems. As latrines and septic tanks get flooded and waste goes into the streets and streams, it can carry a lot of disease, including cholera, dysentery and typhoid.The problem is that the world has only one gold standard for sanitation, which is having flush toilets connected to sewer lines, that are further connected to big and expensive wastewater treatment plants. Growing cities that already have water shortages may not have enough water for everybody to bathe and cook, let alone to flush toilets. So, are these cities going to follow the same path we have taken for the last century in developed cities?