Complex sentence: Other sewage that would have flown into Tijuana river is treated at the Punta Bandara treatment plant; it handles 30 million gallons of sewage a day, however its discharge doesn't meet Mexican water standards sometimes causing closure of beaches as far north as Coronado.
Split into simpler sentences: Other sewage that would have flowed into the Tijuana river is treated at the Punta Bandara treatment plant; it handles 30 million gallons of sewage a day. However, its discharge doesn't meet Mexican water standards sometimes causing closure of beaches as far north as Coronado.