Crunchynut

Yes it’s a land drain - I have them all over my plot. They were laid as you describe -just butted up. Sometimes they are horse shoe shaped. I just pulled them out and carried on.

Again, back to the point of this thread, why wasn’t the manufacturer rep horrified at the thought of rainwater running into their plant? We can all see that such an arrangement will upset the sensitive eco system within it and it won’t work properly and will pollute. They should have instantly spotted the cause, the consequence and the remedial action necessary to get their plant performing to spec.

Your story does back up the original premise of the thread - that these things are legislated for on paper but not understood in practice, and hence the aim of the legislation is missed ….. most of the time anyway. So it comes down to the intelligence and diligence of owners to do the right thing, with not much substantive and reliable intel to support them.

The answer might depend on what problem you are trying to solve? Personally I have used them for about 3 months (so starter dose plus 2 monthly doses) with the hope they would reduce the % solids in my STP and they don’t appear to have made any difference. Note that the STP was and is working fine anyway - I just wanted to see if they would extend interval between pumping which they claim to be able to do. Maybe 3 months is not long enough and maybe if %solids is already high then they can’t be expected to make inroads in that situation, so the jury is out atm.

It’s probably just a push/pull fit, with an ‘o’ ring seal - a strong pull may do the trick. But I understand your nervousness.

Did you just remove the grid over the outlet or did you then pull the trap out? In my experience gunk gets caught up on the exit of the trap, which you can’t necessarily get at by just removing the grid, depending on its design. Most shower traps allow you to pull the trap dip tube out and hence get at the problem area.

This may help. Give it a miss if you are squeamish! https://youtu.be/QHaRbszsSC4

They don’t have to, no. They could just set up once at installation and forget about it, just like other systems. But do you really believe any system works perfectly for their life after initial installation? I doubt it, and that is the whole point of this thread - that, probably, most people are unaware whether their system is working to spec or not, and there is very little information around to help. And 12 months between ‘service’ is a long time for things to be going wrong.

Do you have to throttle back the coarse bubble rate to get that much SSR flow? I have a pumped inlet so by the time the stuff has been pumped there aren’t any lumps (urgh) so coarse bubbles don’t really have a job to do. But even then, if SSR is full chat then I think that would break up any new arrivals. That’s on the newish tanks - I notice on older tanks the SSR just dumps back into the aeration chamber, not the inlet chamber.

I agree - it’s so hard to get to facts and we all do the best we can. At least this forum helps us compare notes and perhaps get closer to what’s right.

Same here. I like it to be just spilling over occasionally.

I agree. That is what I am learning - symptoms can change overnight. Clever things these bacteria. Brings us back to the whole essence to this post - they are hardly ‘install and forget’ if they are to be kept working consistently within their design spec.

I may have been a little contrary for which I apologise to all. I’m just trying to seek understanding beneath what is said. Here is my logic. First, like a say, if inorganic stuff is building up in the bottom of the tank, if you perpetually leave it there then at some point there is going to be a problem. Second, bacteria reproduce at an astonishing rate in the right conditions. I believe a new tank of fresh water will soon react to the food supply (poo). Bacteria don’t need an invitation. Third, bacteria soon die if the conditions aren’t right. If you leave biomass in the tank, which is mostly full of fresh water and very little food, I believe they will just die, or diminish to low numbers that the low concentration of food can support. Just like if you were starting afresh. So, I may be wrong, but my logic says empty completely (notwithstanding the points about tank integrity in wet ground).

I would ask the engineer what leads them to belleve it needs emptying. Is sludge obviously passing over the outlet? Is the effluent cloudy? have they run a settled sludge depth core test? Have they run a test to show that the solids ratio is above limits? I’m not saying it doesn’t need emptying, but if you are concerned then a few probing questions might help.

How do you know this? Science or hear say?

I’m not sure the advice is right. Potentially, the dead sludge at the bottom of the tank has no bacterial qualities. It may just be inorganic stuff, for example. It’s just taking up space and potentially gumming things up. A clean tank filled with fresh water will soon establish the necessary bacteria. In the right conditions bacteria will reproduce rapidly. Just like it did when it was new. I agree with you both on refilling though - in this wet weather, if there is any doubt about whether the tank has been installed with enough concrete in a high water table area, fill it up with fresh water immediately (ie don’t leave it empty to fill up naturally) lest it floats out of the ground. This might be a reason not to empty it completely, depending on how quickly you can refill it. Always best to de-sludge in the summer months if possible, for this reason. By the way, what makes you believe it needs emptying?

Further to this, I’ve found out that some filamentous bacteria can reproduce every 20 minutes. That is, they split into 2 every 20 minutes. This means that you get exponential growth of that type of bacteria - or at least initially, until the amount of bacteria starts to make conditions for reproduction suboptimal and therefore it slows down or stops. So in a 1 hour power outage you might increase the amount of filamentous bacteria in the biomass by 8 times in ideal conditions. Enough to make the level of floc look unusually high? Maybe. Next time I have a power outage I’ll pay more attention. I’m not brave enough to do it deliberately. Please let me know if you observe the same.

You could well be right. I don’t know much about SBR but quickly found some quite informative stuff on the internet. In the document I found they comment that the formation of filamentous bacteria during the ‘idle’ period is offset by a new ‘high food’ influx when the ‘fill’ period commences, which causes the beneficial bacteria (that produce floc that settles well) to prevail of filamentous. So maybe we are both right! Thanks for the comment - still learning…..

Still a lot I don’t understand. A couple of days ago I peered into the settlement tank and beneath the top clear layer I could see the settled floc only about 15” below the surface. Perfectly settled but worryingly high. Next day I looked and the settlement level had dropped to the point where I couldn’t see it. Nothing had changed. Same loading, same overall water level. It hasn’t done it since. The only thing I can think is that that day the power had been off for an hour. Had this caused filamentous bacteria* to grow (the ones that thrive in low dissolved oxygen situations) in such a short time? And can they be destroyed quickly once other bacteria thrive again when the dissolved oxygen (DO) recovers? But if low DO was the problem I would have expected quite a bit of floating sludge because there had been excessive denitrification**, but there wasn’t - perhaps the floating sludge return had been doing it’s job well. I don’t know. *filamentous bacteria form a very low density floc which consumes more volume and hence you would expect the volume of floc in the tank to rise and hence the settled level to be higher. ** denitrification is where, if DO runs out in the settlement chamber, the bacteria break apart molecules containing oxygen to get at it. So, Nitrates are broken apart and the Oxygen consumed and the Nitrogen floats lumps of floc to the surface causing floating sludge. Still searching for more knowledge and answers that allow us to be able to manage our tanks better ……please comment if you have any.

I had this problem a few weeks ago. Exactly the same. It’s what sparked me into doing some research. Here is my take on it : If you observe what happens, and notice that lumps of floc (sludge) spring to the surface in a mass of fine bubbles, then it’s to do with consumption of dissolved oxygen (DO) in the settlement tank. The biomass in that tank is obviously no longer being oxygenated by the bubble diffuser, but the bacteria keep consuming it, so the amount of DO reduces. If it gets too low then they start to go after oxygen that’s in the nitrate molecules (Nitrogen combined with Oxygen). When they break these molecules apart to get at the oxygen, then nitrogen is also released. This accumulates in the floc until there is enough to make the floc buoyant and it floats to the surface. So, you might get this effect if; either overall dissolved oxygen is too low (eg the bubble rate it too low) meaning the biomass in the settlement tank will soon run out (because it was low to start with) and start going after the nitrates. Or, it may be that the bubble rate is fine, but the rate at which the settled sludge is being returned to the bubble chamber for re-oxygenation is so slow, that the DO diminishes just because of the length of time in the settlement tank. What I did was increase the rate of SSR (settled sludge return) and the rate of aeration. Because these two rates work off the one blower and if you increase one the other will decrease, what I do is sacrifice the amount of air going to the coarse bubble diffuser. That’s because on newer Vortex tanks where SSR dumps into the inlet box, I find that the SSR flow agitates the inlet box pretty well anyway, and hence not too much coarse bubbling is needed. It took a couple of weeks to sort itself out, and to cope during this time I set the timer for the floating sludge return to run every 40 mins instead of every 60 mins. That’s my experience anyway, and as I keep saying, I’m an enthusiastic amateur and no expert.

I’m a bit confused by this too. Again, I’m no expert, but this is my take on it: Firstly, the amount of undesirables in the inflowing effluent dictates how much dissolved oxygen in the treatment plant is needed to support the bacteria levels to cope. So I could well imagine that if there is far too much DO for the incoming effluent then, as mentioned above, you would get a cloudy effluent. So, I guess you would want to have a low aeration rate in a tank in this situation. Next, I don’t think it’s a case that the bacteria will all die and never come back - they will die if there is no food but I think they soon re-establish once the food returns. Their reproduction rate is super fast. But, there is ‘sludge age’ profile and different bacteria do their stuff on different ages of sludge (eg some sludge may have just arrived, and some sludge may be days or weeks old). As you say, if there is so much water washing the effluent through the plant, and the biomass isn’t settling because it is being over-aerated and hence partially being carried over the outlet weir, then the sludge will never reach old age and so I can imagine that the effluent is only partially tackled by bacteria that thrive on young sludge only. I guess the solution here is for the tank capacity not to be too small, so that the sludge has a chance of staying in there for at least a couple of days. Finally, as I mentioned earlier, the bacteria in your poo isn’t eaten by the bacteria in your tank. It just dies because it’s not an environment conducive to its survival. But if the environment has never been able to get established because of so much water washing through, then maybe the poo bacteria don’t die. Back to my opening comments on this thread - you wonder how well these plants are operating in the real world.

I had a septic tank until a year ago, that was here when I moved in. The tank worked fine as you say, but unlike you, my drainage field was on level ground and in clay. It’s amazing it has ever worked at all - previous owners must have almost treated it like a cesspool and had it pumped regularly. The STP allows me to discharge to a ditch (I needed an EA permit since the ditch is seasonally dry). Only problem is that people out for a stroll on a Sunday walk right past the outlet, so I can’t get away with anything other than nice clean effluent - which is why I’m becoming quite a nerd on the subject!

I have a Vortex too and have experienced the same with the SSR (settled sludge return). How do you unblock it? I either poke around the inlet to the pipe with a long stick, or dismantle the cross pipe so I can jet some water from a hose down the pipe. It has solved the problem on the couple of occasions it has happened. What do you do? What you have observed re: cloudy effluent is explainable: For good settlement in the settlement chamber you want the bacteria to stick together in a floc (lumps of sludge). The reason they stick together is because the bacteria form a sticky coating that is partly a defence mechanism to there being limited amounts of oxygen available. These flocs are more dense than water and hence sink in the settlement chamber, allowing clear effluent above to pass over the outlet weir. If there is too much dissolved oxygen (DO) then the bacteria don’t build up that sticky coating and hence don’t stick together, so you get fragments left over in the effluent making it cloudy. So, why does a high rate of SSR make the effluent cloudy? Well, because the longer the biomass is in the settlement tank it is obviously not being oxygenated by the bubble diffuser, so the DO balance is kept low. If you increase SSR then more of the biomass gets oxygenated per minute and that might lead too much DO and cloudy effluent. As you know, the good thing about the Vortex is that the big lid allows you to easily see what’s going on (the reason I chose it over others) and that the SSR and aeration rates are adjustable. The frustrating thing is that they are fed from the same blower, so if you adjust one it affects the other. I understand why they have done that - you would otherwise need 2 blowers and twice the energy consumption - though it makes adjustment slightly more intricate and if one goes up the other goes down. If you increase SSR you may need to reduce aeration a fraction more than it will naturally do. Personally I leave the fine bubble diffuser valve fully open and ‘throttle’ it by controlling how much air goes to the coarse bubble diffuser.

I haven’t found anything that specifically mentions that. They do talk about toxicity generally. There are certain types of bacteria (the problematic filamentous variety) and Metazoa (creepy crawlies) that are evidence of toxicity in the plant, but I guess that could be due to many things. The other thing they say is how sensitive bacteria are - how quickly they die but also how quickly they reproduce - and hence how the biology in your tank will rapidly ‘move with the times’, sometimes positively and sometimes negatively. So I guess (and this is very much a guess) if drug residue is killing off one of the native bacteria in the tank, another may start to prosper in its place. It may not be all bad, because, apparently, the bacteria in your tank don’t kill the bacteria in your poo. That dies just because the environment in your tank isn’t conducive to its survival. Who’da thought?! One of their videos talks about additives and whether they do any good. What they say is, that chucking in commercially available powder containing bacteria and enzymes might be beneficial if the contents have been carefully selected to thrive in the STP environment. If they are just any old ‘cheap to manufacture’ bugs then they just quickly die.

Sorry but I think you might have mis-read - they hardly cover anaerobic systems. The only time they do is when aerobic systems turn bad and become anaerobic. This can happen through lack of dissolved oxygen (blower not working sufficiently), or in old sludge where the floc eps (a skin that forms around the bacteria) has thickened and doesn’t allow as much dissolved oxygen to reached through the eps to the bacteria which then become anaerobic as a result, where the rate of settled sludge return is very low meaning it takes too long for the settled sludge to become re-oxygenated by returning it to the bubble chamber, or in big municipal plants where anaerobic regions in their huge tanks are used to force denitrification (where the nitrates are broken apart to release their oxygen because there is no elemental dissolved oxygen) which is desirable to reduce the amount of nitrates in the effluent.