Jane Powerson what goes down our drains.
Tins of food, tennis balls, footballs, and all kinds of plastics are usual, and once there was a motorbike (minus its wheels). These are some of the things that turn up in Dublin's sewerage system, having been popped or crammed down the city's gullies and manholes.
But let's talk about the items that normal householders flush down the toilet (with apologies to those of you who were eating your breakfasts at the start of this sentence): the panty-liners, tampons, condoms, and other whatnots that are part of daily life. Although they may get whooshed away out of sight, they are not gone. They turn up again in the waste water treatment works where they must be screened out and sent for deep burial in a landfill facility. It's better, says Dublin City's deputy engineer Battie White, not to flush away these items in the first place: "Whatever goes in has to be taken out." And in Dublin, that's at Ringsend's waste water plant, which deals with the effluent of 400,000 households, plus all of the city's industry, plus the run-off from about 50,000 road gullies. Depending on the weather, that's between half a million and two million tonnes of waste water every day.
Some objects clog up the system closer to home. Nappies are an obvious no-no, but according to the plumber working in my house today, the most frequent blocker of domestic systems is the toilet-freshening yoke designed to hang over the rim of the bowl in a plastic cage - called, apparently, a "rim block". Small children and butterfingered adults have a habit of casting them adrift, and they subsequently create havoc in the S-bend. The other kind of toilet freshener, the cistern block, is equally harmful, but in a different way. It changes the pH of the water and corrodes vital rubber and plastic components.
That's the end of the toilet talk, but I want to move on to the kitchen sink, and the integrated waste disposal units that gobble up food scraps and vegetable peelings (and unlucky teaspoons). Battie White advises against them: "they are a very, very bad idea. They put stuff into the system that shouldn't be there, adding to the suspended solids and to the BOD load." This last acronym is "biological oxygen demand", the amount of oxygen that is needed to break down the material in the treatment plant. Much of the detritus that goes into an in-sink grinder can be composted instead, to avoid putting unnecessary pressure on our waste water treatment facilities.
Cooking oils and fats also put a strain on the system, as do paints, weedkillers, and all the other noxious liquids that householders think they're getting rid of when they send them down the drain. In fact, it's just the beginning of a long and unnecessary journey.