No matter what kind of treatment plant you own, and no matter how "maintenance-free" it's supposed to be, your equipment can't do without a certain amount of care. Maintenance can be divided into regular inspection and minor maintenance and major repairs and interventions, when it is usually necessary to combine the service with equipment shutdown.
Since regular inspection and maintenance will take more time and you will do it more often, we will start with it. It is advisable to check the treatment plant at least once a week. So at least once a week, open it and see if what is supposed to be spinning is spinning, what is supposed to be bubbling, is bubbling and that the water at the outlet from the treatment plant is clean, or at least significantly cleaner than at the inflow. Since the operator of the treatment plant is obliged to keep a diary, or at least an operating record, it is a good idea to create a record of the inspection once a week. That is, either in a diary or in a notebook of operational records. The range of activities that should be carried out regularly if we want the treatment plant to clean our water, not to smell and to have its life as long as possible, obviously depends on the specific type of treatment plant. The most common type is the activation cleaner.
Activation treatment plant
It is typical for an activation treatment plant that it works with activated sludge in suspension, which needs to be supplied with oxygen by aeration and needs to be maintained in the system, so it must be separated from the purified water by sedimentation and returned to the activation tank. The activities carried out also correspond to this.
Tools
Before we get to work, it's a good idea to get some tools. It is a fan with a sufficiently long handle and a transparent measuring cup with a volume of 1 liter.
Infusion
Let's look at the inlet first. Here we will make sure that the inlet to the treatment plant is not blocked and that we do not have any domestic calamity. There is usually a basket or screen directly under the inlet for catching large undissolved impurities, so-called scum. If we have any scraps, we remove them to the municipal waste bin. In terms of hygiene, scraps are probably the worst thing that is produced at the treatment plant, so we can cover them with chlorine lime in the dustbin. But a better option is not to throw anything that doesn't belong in the toilet. So nothing but feces and toilet paper. Be careful with wet wipes - they also contain artificial fibers and will not fall apart in the treatment plants. It is better to be disciplined at home and not to make any, than to deal with trouble. Our own experience tells us that it is possible to operate a wastewater treatment plant for more than a year without scum forming.
Some treatment plants are equipped with a leveling or settling tank at the inlet, and water is then pumped from it to the activation tank. Here we check its filling and whether the water pumping is working for us.
Activation Tank
The heart of every activation treatment plant is the activation tank. It is sometimes divided into denitrification and nitrification. Here we first check whether the surface is covered with a "blanket" of floating sludge. We then either mix it up, remove it or just pick it out of dead spots. We do not want a hard-to-remove crust to form over time. If we do not observe anything like this, or if we have disposed of the floating sludge, we go to the main one and check the quantity and quality of the sludge. The sludge must not be grey, white or black. The correct sludge is brown in color, has recognizable flakes and settles well. We determine its quality precisely by sedimentation. There is a standard method for this, where we use a liter measuring cup, an ordinary kitchen one is enough (but get your own for the treatment plants, sharing it with the kitchen is not exactly hygienic), it is also possible to use a measuring cylinder. Pour exactly 1 liter of sludge from a well-mixed wastewater treatment plant into this container (it is advisable that the aeration run for at least 5 minutes before sampling). And let it settle for 30 minutes. During this time, we should have a clearly visible sludge-water interface that moves downwards. The sludge thickens at the bottom and clear water should remain above it. If it doesn't, it's a serious problem. If the water above the sludge remains slightly cloudy with small flakes, this indicates disintegrating sludge. If we let the container with sludge stand for a long time, or at higher temperatures this can happen even within 30 minutes, the sludge can rise and float to the surface. This is caused by denitrification, where nitrate nitrogen is reduced to nitrogen gas. It is a desirable process that improves the quality of the discharged water, however, if this happens, it is not a disaster, but we are not able to determine the volume of sludge. Let's assume your sludge settled normally. After 30 minutes, we read the sludge volume (V30) and record it in a diary or record. If we have less sludge than the previous week, it may be a sampling and determination error. However, if the sludge decreases for several weeks in a row, it is a serious problem, because in a healthy treatment plant, the sludge builds up and remains in the treatment plant (it does not go down the drain). So if the sludge is decreasing, we first look to see if it is accumulating somewhere, typically it is a settling tank. If the loss of sludge is connected to the turbidity of the drain, the cause is most likely here, and the sludge is either disintegrating or is not able to form well-sedimenting flakes. The amount of sludge that is suitable to have in a treatment plant is 300-500 ml/l, you can have even more, up to 800 ml/l, but it must not go down the drain. If there is more sludge, it is advisable to remove it from the wastewater treatment plant, preferably to have it taken away by someone specialized. After removing the sludge, leave at least 200 ml of sludge per liter in the WWTP. The treatment plant will then recover very quickly and the sludge will soon increase. Remember that activated sludge is what cleans the water, so it needs to be present in the WWTP.
Landing tank
Activation treatment plants are most often equipped with a settling tank. It is also possible to separate the water with membranes, but then the maintenance is a little different. We mainly check the level of the settling tank. If it is covered with floating sludge, we remove it with a fan (tossing it back into the activation is the best option). There should already be clear water in the upper part of the settling tank. If this is not the case and the settling tank is, for example, full of sludge, something is wrong. This is usually caused by a blockage in the return sludge pump. This is either a mammoth or a centrifugal pump that pumps the sludge settled in the settling tank and returns it back to the activation tank. In addition to the air supply, this is an absolutely key mechanism for the operation of the treatment plant. So we check every time that the return sludge pumping is working. If the settling tank is equipped with a central stilling cylinder, it is usually a source of problems - it clogs. So we clean it regularly. Sometimes this cylinder is equipped with aeration. It is convenient to have it running. It won't calm down and clump the flakes, but at least it won't clog. Some treatment plants have a sieve at the inlet to the settling tank. It grows with biomass and needs to be cleaned regularly. You can try to remove it, 90% of the time it will not have a negative effect on the operation of the dry treatment plant and you will no longer have to do the rather unpleasant task of operating the dry treatment plant. Next, we look at the drain to see if it is clogged and what is the quality of the draining water, but we can usually see this already by looking at the level of the settling tank. In general, it is advisable to check the hydraulics of the treatment plant - i.e. that nothing is blocked, the water flows in our direction, it does not spill into the surroundings, nor does untreated water or sludge fall into the drain.
Aeration system
Aeration control consists of an eye-metric check of whether air is supplied to the treatment plant and, if so, that it is supplied where we want and in the quantity we need. The key is to ensure that the sludge has enough oxygen (if it has enough oxygen it is brown) and that it is sufficiently mixed with air so that it does not accumulate at the bottom. It is advisable to blow under the combs or the comb basket so that the rakes fall apart, and also to supply air for pumping the inflow and return sludge, if this method of pumping is available at the treatment plant. The blower requires more maintenance, follow the manufacturer's recommendations here. Aeration elements have a service life of approx. 10 years. Functional aeration elements deliver fine bubbles evenly over their entire surface. If we have a geyser somewhere, it is often caused by a ruptured element that needs to be replaced.
It may seem like a lot of activity, but most of it is just a brief look at that part of the treatment plants. The weekly inspection of the treatment plant rarely takes more than 5 minutes + in half an hour another 30 seconds to read the amount of sludge and pour out the sludge after determining its amount. It is certainly better to devote a few minutes a week to the cleaning service, when we don't even have to come into contact with something unhygienic, than to deal with some clogged pipes or "blankets" of solid sludge that clog our inlet or outlet.