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I’ve got a much simpler set-up: The gunk goes into a 1000 gallon concrete tank that is totally anaerobic; the tank is 3′ below grade and is wrapped on all sides, top & bottom with 2″ extruded poly-styrene insulation and then wrapped with two layers of 6 mil poly plastic sheating; the water exits to a split valved drainfield that is alternated back from one half to the other every six months. I had a freebie septic pumping done by a friend after eight years of use by four people and only had 4″ of sludge in the bottom of the tank. The effluent is clear, but you couldn’t pay me to drink it!
My local soil is referred to as “gumbo”; it’s heavy thick clay that doesn’t drain at all. I used liberal amounts of rock & gravel in the drain field and shrouded each line trench with geo-textile fabric before backfilling and grading.
It seems to be working well.
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The only real difference between the two types of septic waste systems is the amount of time to break down the organic solids. However, output from any type of septic system DOES NOT NOR EVER WILL MEET DRINKING WATER STANDARDS. Do not drink or put in bodily contact output from a septic system.
septic system output only breaks down the solids (ie: changes BOD). It does not reduce the salt content, metal content, solvents, or viruses. Becareful in putting grey/black water directly on some plants. The salts will eventually kill them.
The current septic systems were invented in the late 1880's in europe, and appeared in the US in the late 1890's. A well constructed septic system has a life span of 40 to 50 years. You then have to completely rebuilt it (including leach field - there is a PhD thesis on this if anyone is interested.).
*David;We have a problem with the municiple water system. It was started as a method to get people to build in the area by providing them a source of potable water. Soon the smart (& efficient) ones learned that it can be a money maker. Who will spend $10k on a well when the city will hook-up for little to nothing?Most (health?) laws prohibit any surface usage of grey water. Sub-t irrigation only.Ever travel to the Cayman Islands? They have dual water supply in many houses. Most well water is brackish, but ok for non-potable usage. The Gov has desalination plants to supply fresh water to everyone, too. The monthly water bill in housing without wells is over $200.00 CI on the company water. The older houses also have cisterns.Doesn't that sound like US & Canadian housing prior to municiple water?Cheers; JE
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This site provides a very useful
source of info. for septic/onsite waste disposal
*California has started to pipe lower quality water to comercial locations...Uphill from most, near the stream,J
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I'm not an Environmental Engineer, but I do design residential wastewater systems in NY. The local health departments don't seem to like ANY system that requires alot of maintenance. You can't blame them, after all, traditional septic systems with absorption fields/trenches require little maintenance and have a long history of satisfactory performance if properly designed AND CONSTRUCTED.(even when the residence is added to in future). My local health dept. official really likes sand filters (single and recirculating) as the outflow is "polished".
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Mr Duval: I too can understand why the health departments doesn't like system that require maintenance (or active components). Because most home owners won't do the maintenance or repair any active components that break. How many active solar systems have we all seen that got shut down because of the failure of some simple part? For the majority of houses with plenty of water and lots of leach field area a traditional system is the best choice, even if it is less efficient (in BOD reduction per gallon of volume). But a few people have limited water available or no place to reinfiltrate (e.g. live on a lava flow). Traditionally those sites are declared unbuildable, even thoough folks in Hawaii, etc. figure out other approaches that work. Sand filters are a great low-tech way to polish waste water. Lots of really cheap surface area for a bacterial layer to develop on.
Figuers: There are multiple differences between aerobic and anaerobic systems - different chemistry happens when bacteria have to use electron acceptors other than oxygen. For instance, methane is generated anaerobically, but not aerobically. While many solvents (toulene, xylene, stoddard's, etc.) are easily broken down aerobically, chlorinated solvents (TCE, etc.) basically don't break down aerobically, only under anaerobic conditions and especially if an appropriate co-metabolate is available. Metal concentrations are typically reduced in septic systems - that's why organic farmers get all bothered by the use of sewage sludge on crops. A variety of plants will uptake metals from the soil. But I agree that one should not count on a biological process to remove metals without lots of study on the particulars of the waste stream. Far better to not flush dissolved metals down the drain, whatever system you have. Salts definitely pass right on through and can build up in soils unless enough volume of water is used to irrigate (that's a whole other topic that Ag Eng's could describe). Many pathological organisms are removed by a septic system - it is a very different environment than the human body and a very competitive one. But, like metals, you shouldn't rely on complete treatment. I hope nobody thought of drinking the water coming out of any such treatment system. I assumed that was obvious. Why trust a complex interaction of bacteria, time, temperature, and chemicals when the city-, well-, or rain-water is probably pretty safe. Although anyone with a shallow well and a neighbor upgradient DOES drink septic system effluent. Hopefully after a long distance percolating vertically and migrating horizontally and with much dilution into the local groundwater. But there would still be trillions of molecules of septic system effluent in every glass of water. There are dozens of PhD theses that could be written on each these topics.
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You guys all sound like engineers so this may sound like a simple question, but here goes. Understanding that the concentrations are relatively minute, do all of these anti-bacterial hand soaps have an adverse effect on the microbes in my septic system?
figuers-- now you have scared me. Are you telling me that the system on my 1952 Cape could go at anytime? Ooof.
Andy
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Lisa asked for more information about more efficient septic systems I referred into in another thread. One of my pet peeves is how primitive standard septic systems are. Several days of residence time and it still comes out stinky into the leach field. With a aerobic (instead of anaerobic) system, I've made 10 gpm of toxic waste site water meet drinking water standards in a 1-hour-residence-time tank. A nice thing for the downgradient neighbors or stream. It also might allow one to build in an area with otherwise inadequate drainage. And, in areas with little water (rain catch absins in Hawaii), it would allow garden uses of treated household water.
The advantage of traditional septic systems is their simplicity (a large concrete box) and that there are many people who can install them, often correctly. But they do so little in comparison to what is possible. Some cities and all space vehicles treat their water to meet drinking water standards by using anaerobic and aerobic processes. I'll post details below. Biodegradingly, David
*A two step process would include a standard septic tank as primary treatment - chunks settle down, grease floats up and there is about a 30% reduction in BOD (biological oxygen demand). Then the water would flow to a second concrete vault but this secondary treatment would be by a "submerged fixed film reactor". A small air pump (e.g. fish tank bubbler) provides oxygen and circulation and "packing" is added to provided surface area for the bacteria to live on. Many companies make prefab packing for sewer districts but when I've needed a lot cheaply or quickly, I've bought corrugated fiberglass panels and bolted them togethers with spacers between (3/4 PVC pipe) to give 1" spacing. Throw some cinder blocks on the bottom of the tank, place the packing blocks on top in a way that discourages water shortcircuiting from inlet to outlet. Place packing so the channels are vertical - it allows dead bacteria to slough off and fall the bottom. When I've used 4 or 5 tanks like this in series with a one-hour total residence time, I've got better than 2,000-fold reductions in BOD and toxic compounds. But tanks in series are more efficient, so if using one tank, use a 500 or 1000-gallon septic tank, even through it is 1-3 days of residence time. While most pathological agents in poop can't survive those two vessels (anaerobic and aerobic digestors are very different environments than the human body), to be safe you could chlorinate the final effluent. Pool and hot tub shops have cheap floating and in-line chlorinators as well as inexpensive water test kits. Chime in with opinions and questions. -David
*What about nitrites?
*David,The type of system you described is very common in unicorporated urban areas just East of St. Louis (in Illinos). I lived there for seven years and all of our household waste water was treated in an aerobic system. There are several brands, the most popular in the area being Jet Aeration sold by Jet Precast in O'Fallon, Illinois. I understand they are a franchisee and that Jet systems are widely available. We had no problems except an air pump failure caused by the ingestion of a non biodregradable component of a female sanitary product. I understand the newer designs have safeguards against this.All of the systems have a clorination chamber into which you put a swimming pool "pill" every now and then. Our system drained into a gully. No odors and no problems. However, in some areas, the health department is now requiring a leach field, i.e., small lots, poor drainage. The leach field can have a surface overflow. The neighborhood we lived in had a mix of conventional septics and aeration systems. When there was odor it was usually someone's leach field going artesian.Cost? Not much more than a conventional septic field if you can surface discharge. Air pumps are good for 10 years or so. Leach fields last forever. There is some operating cost, about the same as a security light. Don't know of anyone recycling the water but I see no problem in concept. I know that cities use this kind of water on golf courses. Doable. But, I think I would buy an engineered and approved unit.
*While were at it, what about phosphorus removal?As an environmental engineer, I appreciate this discussion on domestic wastewater treatment that goes the full mile. Yet, I must add some skepticism:A fine-bubble diffuser will get clogged rapidly and will require frequent replacement. Better to go with a mechanical mixer - not quite as efficient at aeration, but much less maintenance.You probably won't get significant added benefit from the "submerged fixed film" method. Fixed film reactors work best when not submerged, rather, when intermittently wetted.Your best system might be to mimic the most common method used in municipal wastewater treatment systems: activated sludge. This requires a devoted solids settling tank and a means (a small heavy-duty pump) to transport most of the settled sludge back to the "front end" of the process -- the aeration tank.David, I am shocked at your BOD reduction efficiency! Based on the system you described, it doesn't seem possible. Then again, you've probably "breeded" a great strain of bacteria that thrive on your wastewater, which is probably relatively benign compared to the industrial wastewaters that pour into a POTW, often with a chemical composition that impede the growth of benefitial bacteria.No way you're going to convince your public health district to allow you to surface-discharge your effluent, unless you can prove that you have an effective mechanism to virtually eliminate all pathogens. We're talking chlorination, UV disinfection, or ozonation -- all expensive to implement and requiring a lot of maintenance. Plus, you'll have to conduct frequent sampling and analysis, at least monthly, on your own time and budget. If you don't have an analytical laboratory in your home, then this will surely break your budget!Way to go HUSKIES!!!- Displaced Connecticut Yankee in Seattle.
*I've got a much simpler set-up: The gunk goes into a 1000 gallon concrete tank that is totally anaerobic; the tank is 3' below grade and is wrapped on all sides, top & bottom with 2" extruded poly-styrene insulation and then wrapped with two layers of 6 mil poly plastic sheating; the water exits to a split valved drainfield that is alternated back from one half to the other every six months. I had a freebie septic pumping done by a friend after eight years of use by four people and only had 4" of sludge in the bottom of the tank. The effluent is clear, but you couldn't pay me to drink it!My local soil is referred to as "gumbo"; it's heavy thick clay that doesn't drain at all. I used liberal amounts of rock & gravel in the drain field and shrouded each line trench with geo-textile fabric before backfilling and grading.It seems to be working well.
*Hi David,I for one would like to upgrade our septic system to your design. In our town we can have a septic tank that feeds to seepage pits - no leachfield at all. This must be the second most primative system out there, slightly above a drywell. The state hates this, but does not attempt to enforce their regs, and our town building inspector, who is also the health inspector will approve almost anything, except drywells.One question I have - do you ever need to clean or pump the aerobic thank? That could be difficult with the fixed films, but perhaps it's not necessary.Also, would simply adding the bubbler to an existing septic tank have any value in encouraging aerobic decomposition?Another somewhat related question - how are septic systems in Alaska designed to operate in permafrost?Thanks -Rich
*Some of nitrates, nitrites, and phosphates will get used by the anaerobic and aerobeic bateria. To completely remove them if they are in excess requires another step of adding food (sugar, starch, whatever) in an anaerobic chamber. The bugs use those nutrients as electron acceptors reducing them in the process.
*Fred: There are random dump packings available. Like fancy wiffle balls with high surface area to volume. They could be poured in but any future access would be really hard. Cheapest packing available would be sorted 1-1/2 to 2" river-run rock. $15/yard versus $10/cubic foot for the manufactured plastic bits. Just adding air will do something. The walls of the tanks provide some surface area and some bacteria will circulate around in the broth by themselves or attached to little particulates.
*Chris: See my post above about nutrient removal. I avoid really fine bubble diffusers because of the clogging problem you note. Air bubbles in water want to be about 1 cm. Smaller than that and they will coalesce into larger bubbles as they rise. Bigger than that and they will break apart. I usually drill 1/4" hole in PVC pipe. But if you want a non-clogging fine-bubble diffuser, drill big holes in a pipe and hose clamp a length of bicycle tire intertube over the pipe. Having put many little slits in the intertube. If it clogs, the intertube will expand and the scale/bio layer will slough off. I know the big boys use intermittently wetted contactors or activated sludge. But both those approaches requires lots of water pumping and, sometimes, mechanical rotation of the contactor. Not something you're going to do in your back yard. Also activated sludge (more than rotating contactors or submerged fixed film (SFF)) needs an operator to pay attention to the recirculation rates and density of the sludge. Plus a clarifier and a sludge-rated pump as you note.Shocking though it may be, 5 reactors in series are VERY efficient. The last bacteria in line go into scavange mode and suck up every last bit of food (to below detection for benzene (0.5 parts per billion) and total hydrocarbons (50 ppb). You would not do as well in a one tank system. It definitely helps to seed the reactor from a variety of sources - the local POTW, another septic tank, the local groundwater and surface water, etc. Let them sort it out and the combination of strains that do best with your water chemistry and food source will emerge victorious. And you're right about toxins. Moderate concentrations of bacteria food (like domestic sewer) is easier to treat than industrial discharges with biocides, heavy metals, high and low pH, etc.I agree that permitting would be an uphill battle. And you'd probably get slapped with some onerous monitoring requirements. I'm thinking more of the person who lives outside city limits who wants his/her own swamp to support more wildlife or their leach field to smell better.Native San Francisian displaced to Seattle and now enjoying Alaska. Go Huskies, Mush! - It's 1,100 miles to Nome. ("Hike!", actually). I only mush casually, but have several friends who have completed Iditarods. -David
*Richard: At least you got septic tanks locally. Alaskans living "off-the-grid" just use outhouses.Like a standard septic tanks, solids will build up - dirt and mineralized bits that settle out. So you need to leave some passages for the honey-bucket truck to slurp it out. Thats why I suggest blocks under the packing - to provide volume for settled soilds. You can do this with a large and powerful shop vac (I have). But wear a mask because of splashes and be prepared to catch s--t, so to speak, from the next user of the shop vac. Shop vacs also make good sampling/transport containers for seeding the reactors from other septic tanks or the local sewer treatment plant.Yes, just adding the bubbler would help (see above post) but it would best be done in a separate tank, even if that second tank didn't have any packing in it. (Anaerobic and aerobic process acheive different things. The combination is better than either one.In Alaska, south of about Fairbanks, septic tanks are located deep - 5 to 8 feet down and are located in an area that won't be plowed of snow. A plowed driveway freezes much deeper than unplowed land. I'm going to put some rigid foam over mine as well. Warm bugs are happy, busy bugs. North of Fairbanks you get into permaforst and things get weird. In Barrow; water, sewer, and gas are conveyed in aboveground, elevated, insulated, heated "utilidors". Above ground for access, elevated to protect the permaforst from melting, and heated to keep the s--t moving downhill. -David
*How about a composting toilet for the s--t and a gray water system for the rest?
*The amount of water and energy savings that could be done is huge. If we had a more piping systems, at least. As Ron mentions, poop and pee down one pipe (or hole) and grey water down another. Likewise on the supply side. Why not have three supply pipes from the water company? About 3 gpd of very high quality water for drinking/cooking only. 50 gpd of wash water (soft) for washing hands, bodies and clothes. And 200+ gpd of bad tasting, potentially hard water for watering the yard. Yet water companies have to provide 250 gpd of good tasting water so people can water the lawn. It will never happen because the plumbing would be prohibitive and the distribution system would have to completely overhauled. But you can plumb your gray water for garden use. And have a whole-house Alhambra system if you want to install the plumbing and two facuets at every sink.
*Hi David, Thank you for the detailed replies to all in this this thread! If I can sweet-talk my buddy with his excavtor to add a second tank, I'll be emailing you for more specific details as I think more about it.I've wondered if an outhouse is more primative than spetic with seepage pits. With so little waterflow in them, the s--t stays in one place. A neighbor of ours uses one, and every spring moves it and plants a tree in the hole. He has some really nice trees! But I suppose pathogens could easily get into the surface water. After an intense bout of Giardia thet I got from shallow well water (hand dug) a while back, I think your treatment systems should be required...It's interesting to hear about the systems in Barrow. I've worked at South Pole Station, (headed back this November), and there all liquid and solid waste goes thru a buried utilidor then straight into the ice, where it has formed a cavern by melting since 1974. It's called Lake Patterson after a plumber who has worked there over the years. Yuccch!
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Andy, you're right, the concentrations would be very dilute. When the anti-bacterial soap is on your hands, it's only been diluted into a tablespoon of water. Diluting that into a 500-gallon septic tank would reduce its concentration an additional 100,000 times. Of normal households activities, I'm most cautious about using akaline or acidic drain cleaners and about lots of laundry detergent - especially if it is not recommended for septic systems. Of abnormal activities, I'd warn against dumping most chemicals down a septic system - fuels, solvents, paints, and especially pesticides and herbicides. Take them to household toxics dropoff (best) or a friend's house on the municipal sewer system (not as good, but far better than a storm drain).