A sewage leak that has spilled an estimated 20 million gallons of wastewater into a Contra Costa County wetland could have considerable ecological consequences for the fish and wildlife populations that call the Suisun Marsh home. Among the water that runs through our sewage system is washed-out shampoo, sudsy dish soap and remnants of medications — and all of those can be harmful to the fish and birds, according to Sejal Choksi-Chugh, the executive director of ecological watchdog Baykeeper. The leak was discovered Monday, spurring repair efforts this week, but it is believed to have started weeks earlier. Choksi-Chugh said she worries about how the influx of untreated water that has seeped out of the Delta Diablo Sanitation District’s broken pipes will affect the environment.