The city built its drainage system in the early 1960s. Through the 1970s civil war and Khmer Rouge era, the system fell into disrepair.
That was nearly 40 years ago, when the city was a fraction of its current size. So most of the drainage system is a lot newer than that, and a whole lot of it has been updated and rebuilt by JICA and the municipality over the past decade.
Cambodia’s census agency found that of the 92.9 percent of Phnom Penh households that have a toilet, just 19.7 percent have a septic tank while the rest are connected to drainage facilities. Typically, larger developments such as planned communities or sprawling satellite cities on the urban outskirts are more likely to include septic systems than tower blocks in the inner city, where space is at a premium.
I don't believe those statistics, and they come from an unspecified census. I don't know what they mean by "tower blocks in the inner city", unless they mean older multi story shophouses. Modern condo blocks all have their own septic tank systems, and space doesn't matter as they are built under the structure. Any new construction has to include a septic-tank system. The canals that carry waste water do not have a whole lot of raw sewage in them, or they would smell a whole lot worse. It's mostly just run-off from drains and septic tanks, that's why it's black rather than gray with turds floating in it. Of course the city's expansion is putting a lot more strain on the system.
The entire cities waste water is just being pumped into lakes?!
Yeah, that's where all those stinky canals end up, at the pumping stations on 271 and 598, the two bigger ones are being upgraded at the moment. As the article explains, that actually worked when Boeung Tumpun was more than 1000 hectares. I lived nearby for years and while it stunk a bit near the pumping station outlet, a hundred meters or so into the lake it got a lot more clean looking. It was a lovely place before the road and reclamation projects, with just a few canoes out harvesting, fishing, and an amazing amount of wildlife:
And all that waste must go somewhere. The city does not have a sewage treatment plant, so the effluent mostly flows straight into large lakes in the south — Boeung Tompun and the adjoining Boeung Choeung Ek — where wild and cultivated aquatic plants growing on the surface act as a natural filtration system. Tiny organisms that live on the root of the floating plants feed on both organic matter and harmful pathogens found in sewage, turning the effluent into clean water. But this microbe-reliant method, which is both cheap and efficient, comes with a caveat.
“The capacity of the natural treatment process depends on it not being overburdened by too much sewage,” says Taber Hand, director of Wetlands Work, which builds treatment systems. “When the wetlands area becomes too small, or the volume of sewage input increases due to a growing population, the microbial community does not have sufficient time … to make the water very clean.”
Now much of the northern part has been reclaimed so there's just a narrow channel for the northern kilometer or so now. They'll probably pipe it all in and build over it, but it's basically just pushing the problem further south. There used to be giant piles of foam on the water just south of the pumping station, now you can find them way further down where the Hun Neang Boulevard intersects. It was always a sketchy area for farms, I believe the water also contains a lot of other contaminants and heavy metals etc. The locals used to tell me that the Morning Glory was harvested for pigs, then I figured that not so many people keep pigs around the city.
The plans for the area blew me away, I had seen some CGI plans for Marinas and a new satellite city long ago, but then at one stage it was stated categorically that most of the wetlands would be preserved an kept for their filtering role. It makes sense to push the development south, but without some major sewage treatment plants being built it will be messy. Nobody wants to jetski on that stinky, sludgy mess.