Outdated Sewage Technologies Are Still in Wide Use in the US
The Romans developed a technology, still used today, called combined sewers. It is effective at what it was designed for–moving sewage and stormwater off city streets and out of the city as quickly as possible.
London copied this technology beginning inthe 1800s and many US cities built these combined sewers from the 1850s to about 1920. The combined sewage and stormwater was discharged directly into rivers and lakes accomplishing the designed purpose of getting it out of the city as quickly as possible. This was considered good enough at the time, and treatment was added later in some systems.
For systems that have added treatment, the combined sewer system works fine–when the weather is dry. But when it rains, combined sewers receive stormwater faster than treatment plants can handle it. Some of this combined sewage makes it to the treament plant, but if there is too much rain, as there often is, the treatment plant can’t handle the overload and excess combined discharge simply goes to the river or lake. In a word, some of the discharge, raw sewage from homes, flows untreated directly to the lake or river.
There are more combined sewers still in use in the US than one would imagine. New Jersey, for example, has almost 300.
When water suppliers speak of the need for “infrastructure upgrade,” getting rid of combined sewers is one of the things they’re talking about.