Wednesday, September 17, 2008

Three Posts in One


The above line sounds much better when Van Morrison sings it then it does in print. The linked article makes you wonder about swimming on Irish beaches, or fishing in their streams. I know our firm actually almost went into a contract with Ireland on their waste water plants until we found out they had no or very low effluent standards and therefore did not want to pay for good treatment.

So here is what that article means. Ireland has few secondary treatment facilities. That is technospeak (yes, even turd herders have their own language). Primary treatment means raw sewage comes in and has a settling chamber and/or a bar screen to remove solids in sewage. You know, poop, toilet paper, credit cards, rings, false teeth, prophylactics (if you're lucky--I know it sounds silly but we used to have bets on manual bar creens, yes, you clean the gunk off with a rake, on the colors of prophylactics. Bright orange, striped, psychedelic, white. Some suburbs must have had a lime green rubber factory in town. Okay, doing this job gives you a twisted sense of humor. We in the field know this. I won't go into nicknames of common waste products, but I will say prophylactics somehow inflate like balloons in aeration basins and unlike the fear caused by the leech creature under the foam in the X-Files episode, it gets rather comedic to see orange and other brightly colored almost-balloons floating, but I digress). Primary treatment is settling solids, maybe some chlorine for disinfection, maybe not and discharge. Solids then get landfilled, compossted or spread on farmer's fields for grain crops only. In the States, there are few primary plants anymore. Anchorage and maybe San Diego come to mind.

Normally, there is secondary treatment where lagoons hold the solids and nature's processes (grow algae, oxygenate that way) help lower Biochemical Oxygen Demand and ammonia. There are advanced secondary treatment methods where blowers provide extra oxygen where ammonia is converted to nitrate, which is less toxic. There is even more advanced treatment where you force starve the bugs (bacterial floc) and they actually then take up extra phosphorus and the nitrate converts to nitrogen gas and oxygen. The bugs use the O2 for food and nitrogen gas goes to the air. The phosphorus stays in the bug-bodies and are disposed of in compost or again used for fertilizer. The effluent is generally clean and disinfected.

So what is in Ireland is a bunch of primary treatment. It beats cesspits, but not by much. Yuck!

Combined Sewer Systems

Sorry, but it seems as though today is a bad sewage pun day. There was an article in a trade journal last Friday that caught my eye. Most people don't realize that many older wastewater systems have what are called combined collection systems. That means the storm sewer flows into the sanitary sewer. In the west where there is newer construction, for example Denver and Tucson, most sewerage systems are separated and storm drains go directly to creeks and rivers. In the Midwest and the East the storm sewers go to the wastewater plant. Why is this an issue? Let's say it takes 3 days to adequately treat sewage. You have tankage for 4 days. You get a big rain and your normal flow of 2 Million gallons per day (MGD) goes to 3 or 4 MGD. Remember you have tankage for 8 million gallons. So at three million gallons per day means you are short tankage for treatment after 2.3 days of higher flows. Most plants do not have one or two days extra tankage. They may have one-half day if you are lucky, if not right at maximum tankage. I have seen big rain events take flows of what is normally a 1 MGD plant to 10 MGD. The untreated sewage then just goes right through the plant and out into the rivers and lakes. and if you are in a built up area it costs a lot more to separate the lines. I don't know what Chicago is like, but after seeing all the rain they had, you have to hope they have separated sewerage systems. Cleveland has many combined sewer systems so if they get heavy rain, Lake Erie may take a hit. Heavy rain in Iowa goes to the Mississippi, washing out wastewater plants on the way.

Okay, it is diluted, but remember it is a drinking water source for someone downstream. In this year of elections, also know that most infrastructure repair estimates nationally are for roads and bridges and do not take into account water and sewer systems. Towns, cities and counties have to take the expense hit. The expense mentioned in the article is not an uncommon cost.

More Combined Sewer Systems

Over the weekend, I mentioned the problems with combined sewer systems and what could happen if a large rainfall occurs. Here is one such occurrence. Someone had asked (and I am grateful for questions because it means that people actually read some of these things) if consumers and environmentalists are rallying around these necessary repairs or if this is even an action item. Sadly, replacing combined sewers with separate storm and sanitary sewers is so far down the infrastructure repair list, it is not even an issue. Many small and large communities can barely make the financial commitment to make wastewater plants meet tighter specifications which come out with almost every plant permit renewal (5 year cycle). The funding is almost unavailable to upgrade sewerage systems.

The first article in my last post about Keokuk, IA stated it would take maybe 17 years to upgrade the sewer system. That is a long time and a very expensive process. One would hope that City planners can at least make new development have separate systems and then as areas are redesigned and upgraded with new roads, power lines, etc. then be made current at that time, but that requires long-term planning. I hate to sound cynical, but even local political cycles require reelection and if rates and costs go up too much, you won't get reelected. Most residents are not really proud of a brand sewage collection line, as opposed to a park. You see a park and ooh an ahh over it and the trees and flowers and wildlife. But a sewer line, big deal.

so much for the optimism and trusting human nature report for the day.


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