Were the Romans the first to built sewers?

It is estimated that Roman Sewers were invented between 800 and 735 BC. The open channel Cloaca Maxima is guessed to be built sometime between the sixth and fourth century BC. It was built to drain the low lying land that was in the Forum. From the Cloaca Maxima, a network of sewers was gradually built. Most Roman sewers emptied into the Tiber and were for draining water above and below ground. Waste from people was thrown into the street and most was swept into this network of sewers with aqueduct water.

My source is the Wickipedia article called Sanitation in ancient Rome. You can find out much more there if this didn't fully answer your question.