Private citizens built Boston's first systems, designed, like the Cloaca Maxima and the Grand Egout, to drain cellars and swamps. Bostonians soon grew weary of the constant repairs those wooden sewer lines required and undertook a sort of public-private partnership by issuing construction permits for sewers; everyone who wished to connect a drain had to share in the cost, and the contracts stipulated requirements about pavement reconstruction.
Philadelphia had a system of culverts and some underground sewers by , and New York City started putting a few sewers underground later in the century. Human waste, though, remained mostly a personal matter of cesspits and privies.
Sewers really took off in , with John Snow's discovery that the London cholera epidemic was caused by sewage-tainted drinking water. With advances in microbiology, people began to understand that human waste carried disease in the form of microbes, and increasingly they wanted to protect themselves from their sewage.
What's more, the introduction of reliable water service in the 19th century and the spread of the modern flush toilet the British Public Health Act of , which required every home to have some kind of sanitary arrangement, listed "water closet" as one of the alternatives to an ash pit or privy vastly increased the amount of wastewater households generated.
Cesspits and privies that had already created offensive nuisances now produced vast, vile-smelling seepages, overwhelmed by the new volume of water. And it wasn't just toilets, either--connections draining sinks and tubs began overwhelming sewer pipes, too; in Boston tried to slow the tide, literally, by passing a law requiring a doctor's order for every bath. As cities grew in size and density during the Industrial Revolution, they all had to build more, and better, sewers.
The cholera epidemic wasn't motivation enough for London, but the "Great Stink" of , when the Thames smelled so bad that Parliament considered relocating, got the city government's attention; it built new sewers in the s and '60s to carry waste downstream from central London. Brooklyn introduced sewers in , and Chicago not long after. Boston, still largely building sewers privately, had about miles of sewers in ; by that had expanded to miles, and new houses were expected to connect to the system both for pump and washbasin waste and for the human waste now going into flush toilets instead of privies.
Every city had its own problems and its own characteristics. Some of Boston's sewers had outfalls dammed by the tide 12 hours of every 24; others, built by unscrupulous contractors in land reclamation projects like the Back Bay, sagged and lost their downhill slope, causing settling, clogs, and backups. Sylvan Seattle had pipes made of wooden staves--and faced a tide problem so severe that at certain times of day toilets became foul geysers; eventually the city simply rebuilt itself higher than its sewer pipes.
In Chicago, the outfalls of the sewers made such a mess of Lake Michigan that during large rainstorms the plume of tainted water flowed all the way out to the intake for the water system. In response, engineers built a series of canals and reversed the flow of the Chicago River, turning it from a drainage into Lake Michigan into a flow from Lake Michigan toward the Mississippi. They also moved the intake farther out into the lake. All these "solutions" merely moved the problem. As one historian said in describing Boston's covering a brook filled with sewage and routing it to the Charles River rather than directly into Boston Harbor, this "somewhat lessened the nuisance caused by it, or at least transferred it to another locality.
Lennox, Massachusetts, built the first such system in , and Memphis built one in Since then, that's what everybody has built. Raleigh laid its first sewer pipes in Fayetteville Street, Raleigh's main road, wasn't paved until , at exactly the same time the first water pipes were being laid; where water pipes go, sewer pipes soon follow.
The privies of Raleigh's population of barely 10, almost certainly had not yet polluted the soil enough to foul its wells, and the new sewer pipes, running north to Crabtree Creek and south to Walnut Creek, would not have discharged more than the streams could absorb.
A stream running at about 6 cubic feet per second can absorb the waste of about 1, people, so to support 10, people the two creeks together would have had to flow at around 60 cfs. Currently, on a dry day in a dry month, they flow at about 75 cfs.
Now, with 2, miles of pipes all heading roughly southeast to Raleigh's wastewater treatment plant, the sewer collection system turns out to be the only infrastructure stream that follows that natural tree pattern that I'd expected to find everywhere. The leaves are houses, connected by 4-inch service lines to 6- or 8-inch mains that run mostly beneath streets, and then to , , or inch collectors that start out along streets but head downhill to creek basins, leading to larger and larger pipes and finally to the plant.
I sat down with a friendly GIS expert to check it out. The GIS map easily showed me the path of my own wastewater: the 4-inch lateral in my yard--the same pipe that "flushable" wipe clogged--runs into an 8-inch main, which heads downhill along my street until it crosses the Pigeon House Branch, down by the pool I like to sit by. It runs along the Pigeon House until it joins a inch PVC east of town the path is following rivers by then, not roads , and thereafter joins larger and larger pipes--some made of PVC, some of reinforced concrete, some of ductile iron.
Eventually this stream hits the dual inch reinforced concrete pipes that head directly to the sewer plant, though those sometimes separate into three or four pipes, for ease of maintenance. It's simple and, especially after the spaghetti tangle of the water lines, rather satisfying. It's much like the stormwater system, if every ravine in every drainage basin remained piped and they all came together in one place before entering the Neuse.
To find out what happens in these pipes, I talked to Raleigh's dean of pipage, sewer collection superintendent Hunter "Gene" Stanley. Combined systems manage overflows with relatively simple mechanical junctions called regulators: basically weir dams in pipes or junction boxes. A weir is nothing more than a low barrier for steering water. When flow is routine, the dam routes it through pipes to the treatment plant; during large rain events, the flow of mixed stormwater and wastewater rises high, overtops the weirs, and flows directly through outfalls to rivers or lakes.
Such an event is called a CSO, or combined sewage overflow. New York dumps about 40 billion gallons of CSOs into its rivers and harbors every year.
But before you draw too much comfort from Raleigh's system having to convey only sewage the plant treats about 45 million gallons per day that are generated by the , or so customers connected to the system; it's rated for 60 million gallons, and it's being expanded to 75 , consider this: The increase in flow caused by nothing more than rainfall and street flow coming in through manhole vents in low-lying areas can nearly double the flow to the treatment plant.
Though catching and correcting the breaks and overflows are an unavoidable part of his job, Stanley stays focused on preventive maintenance. Stanley grew up in rural North Carolina and has called his preventive maintenance management "an ol' country boy work system"--he copies pages from the map book of his system and gives them to his crews. When the crew has flushed and inspected every line on the map, it comes back. The department logs its maintenance in feet per day, and it likes to reach , feet per month if it can, meaning that every pipe in the system gets a look-see once every few years.
GIS keeps the maps updated, of course, but Stanley's system has been working since they were using nothing more than blueprints and as-built surveys; finding that what's an 8-inch pipe on the map is really a 6-inch is just part of keeping on top of things. That's why you carry different-size saw blades in your truck. Stanley says a sewer is a simple thing: The pipe needs to drop about half a foot per feet of length, a slope of 0.
Bigger pipes inches or larger--can slope even less. But they all must flow downhill, powered by gravity, which is why sewer pipes so commonly crisscross the stormwater drainages: Raleigh Public Utilities Department director Dale Crisp calls all the sewers that run in a particular drainage a "sewershed," which for a while became my favorite new word.
Of course, if wastewater pipes followed only natural gullies, the mains would eventually have to parallel the river, and for many reasons, from aesthetics to the catastrophic results of a spill, nobody wants that.
The system generally moves downhill, but pipes sometimes need to cross rises. So the city has more than lift stations, where the contents of pipes are pumped to join other flows or where wastewater from lowlying areas collects in sumps. When the water gets high enough, it trips a float valve and a pump clicks on and lifts it up a hill--kind of like your toilet, only this float valve starts the flush instead of stopping it.
I visited one lift station, a by foot rectangle of electrical boxes that look like a central air-conditioning system behind chain-link fences between two houses, controlling an underground sump; even when it's pumping, if you were more than 10 feet away you wouldn't hear it. The station has a backup pump and a generator to power it, plus a little antenna to send information back and forth to the supervisory control and data acquisition SCADA system at the treatment plant; that's plenty of equipment, but just the same, if you weren't looking for it you wouldn't know it was there.
A much larger station sits on the trunk line, giving a lift to pretty much all of Raleigh's waste on its way to the plant. It's underneath a highway on-ramp, and though some people suggested I could find it by following my nose, it didn't smell when I went out to visit it. Stanley hands over a laudatory profile of Raleigh's sewer maintenance department in a recent issue of Municipal Sewer and Water magazine, then hands me off to Robert Smith, a sewer monitoring supervisor and asks him to show me around.
First things first: We walk the yard, checking out trucks. Sewer guys basically do three things: They perform maintenance, they respond to crises, and they "TV" pipes, sending tiny little vehicles with cameras on them up the pipes to check both their condition as part of general maintenance and whether the crews who claim to have recently maintained them have actually done so. Smith shows off the department's various trucks. Rodder trucks have a spool of linked rods, a sort of long chain that the workers feed into a manhole and then rotate, just like someone cleaning roots or a clog out of your drain at home.
Some rodders have cutting blades or spiral grabbing implements to clear roots or debris. Flushing trucks carry enormous water tanks to feed high-pressure hoses with spinning heads on the end: Workers feed the hose into the system, usually past the next manhole, and then turn on a pump.
Water pressure starts the head spinning, spraying water at thousands of pounds of pressure per square inch back toward the truck as the truck pulls back the hose, scouring the pipes along the way.
Standard now is the combination truck, which carries tanks of water for flushing and a garbage-truck-size tank for postflush water, which the truck vacuums up with a huge tube that hangs from a derrick over the cab like an elephant's trunk. The driver eventually empties that tank onto a pad in the parking area, Smith explains; water drains off into the sewer system and the cleaned-out debris--tampons, bricks, gravel, roots, supposedly flushable materials--gets loaded into a dump truck once a week and sent to the landfill.
Smith marshals those vacuum trucks when Raleigh has a sewage overflow, too. Another truck he calls a blockbuster has a water hammer--a pipe that uses water to rhythmically pound and break up large blockages. Finally, he shows me a sort of souped-up golf cart that provides access to the many parts of the system that, because they follow ravines rather than roads, are not easily reached by regular trucks.
But we're standing in a parking lot while people are out in the field, rodding sewers. Our first stop is a highway off-ramp, where two flush trucks and a pickup are parked behind orange cones. Several men wearing hard hats, green mesh vests, and rubber-palmed gloves manage a hose coming off a spool on the back of one of the trucks and running to a manhole 20 feet down a steep ravine. A hundred yards away, two guys stand at another manhole looking out for the spinning head of the water jet, which Smith says is called a Warthog.
Once it's past, the guys still at the truck turn on the jet and the spool to start reeling it back in. Over the roar of the truck engine Smith explains that on the way out the head sprays as a sort of presoak; "on the way back, it's like a broom.
It looks like you sprayed foam on that pipe. Where the vacuum trucks can't reach a manhole, the crew flushes debris downstream to one the truck can reach.
That's sewer flushing, and the sanitation department does it all day long. Ever since the Hamburg sewers first captured tidal water and then released it all at once to flush out debris, the basic idea hasn't changed much: You use water to flush, you use rods or hooks to attack clogs, and, as Ed Norton sang, you keep things rolling along.
Smith packs us back in his pickup and we drive to a parking lot and a box truck with a picture of a fish on it. The three guys in the truck are going to TV a pipe: Mike is preparing the camera and the screens in the back of the truck while Wayne and someone who introduces himself only as "the Rev" open the manhole, popping the cover off easily with a metal hook.
Wayne and the Rev then retrieve the camera from the truck. With six tiny rubber wheels and an inquisitive single eye, it looks a bit like the Mars rover vehicle, only tiny and dangling at the end of a wire. When they come back to the manhole Wayne and the Rev are shocked to find it suddenly filled with sewage. This kind of backup indicates a block in the 6-inch pipe at the bottom of the manhole, though it drains away as fast as it backed up. A few moments of observation shows two things: The backup comes and goes rhythmically, meaning there's a pump station upstream that sends a pulse of wastewater every couple of minutes, and the blockage is a bunch of pieces of some solid substance that nobody can identify.
Out come spoons--hooked, perforated shovels on the end of foot handles. Wayne, Robert Smith, and Eddie, another supervisor who has arrived, take turns scooping, pushing things back and forth between rushes from the pump and pulling them out with an awkward hand-over-hand motion that keeps the gunk barely balanced on the edge of the spoon unless you knock the handle against an overhanging tree branch.
It's like using an iced-tea spoon to fish olive pits out of a bleach jug at the back of a cupboard.
The stuff turns out to be congealed grease, and pieces of it are sufficiently solid--and sufficiently far up the 6-inch pipe--that they block the progress of the camera every time the Rev dangles it down there and tries to get it running. The vacuum nozzle can clear the manhole but can't pull grease out of the pipe and it resists everything else they've got, so the crew finally gives up on TV-ing that pipe for the day, until they can clean the pipe--possibly by using a bucket truck which feeds a cable past the debris and drags a bucket from one manhole to the next, pulling before it the kind of grit and large debris flushing just doesn't get or possibly by sending someone down there in the hope that a simple scoop into the pipe will clear the debris.
Sending someone down a manhole, though it's only about 8 feet deep, requires confined spaces training, extra supervision, and ventilation equipment--sewer gas contains methane and hydrogen sulfide, and it has killed workers as recently as Smith shows me video footage from another TV-ing expedition that shows long traverses down shiny pipes half full of dull gray water.
The color makes sense--much more of it comes from your washing machine and shower than from your toilet. Though most blockages are caused by grease or roots, the talk naturally turns to memorable clogs, and I hear about mops, golf clubs, firewood, riprap, and even a refrigerator that have had to be pulled out of manholes. If you release wastewater directly into the environment, things get very smelly very fast.
It contains harmful bacteria. Human waste naturally contains coliform bacteria for example, E. Once water becomes infected with these bacteria, it becomes a health hazard. It contains suspended solids and chemicals that affect the environment. For example: Wastewater contains nitrogen and phosphates that, being fertilizers, encourage the growth of algae.
Excessive algae growth can block sunlight and foul the water. Wastewater contains organic material that bacteria in the environment will start decomposing. When they do, these bacteria consume oxygen in the water. The resulting lack of oxygen kills fish. The suspended solids in wastewater make the water look murky and can affect the ability of many fish to breathe and see. The increased algae, reduced oxygen and murkiness destroy the ability of a stream or lake to support wildlife, and all of the fish, frogs and other life forms quickly die.
No one wants to live in an place that stinks, is full of deadly bacteria and cannot support aquatic life. That's why communities build wastewater treatment plants and enforce laws against the release of raw sewage into the environment. Private Treatment: The Septic Tank In rural areas where houses are spaced so far apart that a sewer system would be too expensive to install, people install their own, private sewage treatment plants.
These are called septic tanks. The tank looks something like this in cross-section: In this picture, you can see three layers. Wastewater comes into the septic tank from the sewer pipes in the house, as shown here: A septic tank naturally produces gases caused by bacteria breaking down the organic material in the wastewater , and these gases don't smell good. The following diagram shows an overhead view of a house, septic tank, distribution box and drain field: A typical drain field pipe is 4 inches 10 centimeters in diameter and is buried in a trench that is 4 to 6 feet about 1.
The gravel fills the bottom 2 to 3 feet of the trench and dirt covers the gravel, like this: The water is slowly absorbed and filtered by the ground in the drain field. Urban Wastewater Systems In urban and suburban areas where people are packed closer together and where there is a lot more wastewater to treat, the community will construct a sewer system that collects wastewater and takes it to a wastewater treatment facility.
Here's what each stage does: The first stage, known as primary treatment , does the same thing a septic tank does. It allows the solids to settle out of the water and the scum to rise. The system then collects the solids for disposal either in a landfill or an incinerator.
The second stage, known as secondary treatment , removes organic materials and nutrients. This is done with the help of bacteria -- the water flows to large, aerated tanks where bacteria consume everything they can.
Typically, the third stage will use chemicals to remove phosphorous and nitrogen from the water, but may also include filter beds and other types of treatment.
Chlorine added to the water kills any remaining bacteria, and the water is discharged. Measuring the Effectiveness of a Treatment Plant The effectiveness of wastewater treatment plants is measured on several different scales.
Here are some of the most common: pH - This is the measure of the water's acidity once it leaves the plant. Ideally, the water's pH would match the pH of the river or lake that receives the plant's output. BOD bio-chemical oxygen demand - BOD is a measure of how much oxygen in the water will be required to finish digesting the organic material left in the effluent. Ideally, the BOD would be zero.
Dissolved oxygen - This is the amount of oxygen in the water as it leaves the plant. If the water contains no oxygen, it will kill any aquatic life that comes into contact with it. Dissolved oxygen should be as high as possible and needs to cover the BOD. Suspended solids - This is the measure of the solids remaining in the water after treatment. Ideally, suspended solids would be zero.
New regulations have been written by the MWRA to control the amount of toxic chemicals that companies can discharge into the sewer system. The MWRA's Toxic Reduction and Control Department is responsible for monitoring and enforcing the regulations and imposes fines against industrial polluters. The MWRA also works with industries to encourage reductions in the use of toxic chemicals that might be discharged into the sewer system. Households are also an important source of toxic chemicals due to the careless dumping of toxic products down household drains.
Used motor oil, pesticides, paints, solvents and even many household cleaners pose significant hazards to the environment. For most household jobs, less toxic alternatives are available. About MWRA.
Water System. Sewer System. Harbor and Bay. School Program. Contact MWRA. The treatment process is as follows: Collection and Pumping Sewage is piped from communities to several headworks where bricks, logs and other large objects are screened out.
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