Welcome to our mini-series on wastewater treatment plants in winter. In the first part, we will look at the difficulties that winter traffic brings. Other parts will then be devoted to individual types of treatment plants and equipment and their proper winterization.
Autumn is in full swing, the days are getting shorter and the trees are shedding their leaves, a sure sign that winter is slowly approaching. And it's high time to prepare not only the garden for winter, but also the wastewater treatment plant, septic tank or cesspool.
How much you have to hurry with the preparations depends mainly on the climatic conditions. While ground freezers do not fundamentally endanger operations, it is necessary to have everything winterized before the arrival of permanent frosts. So mountain cleaners have high time now.
Another important circumstance is whether you will produce wastewater in winter or not. If your wastewater treatment plant or other facility processes wastewater from a still-occupied family home, the winter measures will be significantly smaller than in the case of a wastewater treatment plant at a cottage, where you do not go at all or only once or twice in the winter.
Winter pitfalls
The main problem of the winter season is that it is cold. This surprising fact has several consequences that affect your treatment plant:
- Water can freeze
- Bacteria work slower
- Access to the treatment plant can be problematic
So, now we'll break them down in a bit more detail.
Freezing water
Water freezing is a fairly common phenomenon in our latitudes, but it generally has unpleasant consequences in the wastewater treatment process. The worst possible situation is the freezing of the wastewater that we want to clean directly in the facility. Then not only do we not clean anything, but we can't even produce more wastewater, because the road is impassable, blocked with ice. Then you don't flush, you don't wash the dishes or you don't drain the bathtub after a bath.
Honestly, it's not very often that an entire treatment plant freezes. Why? Most wastewater flows out relatively warm, moreover, water has a fairly large heat capacity, so it has to give off quite a lot of heat to the surroundings to cool down by a certain degree. You certainly have the sewage system located in a non-freezing depth and the wastewater treatment plant as close as possible to the house, so that heat loss is as small as possible. If you drain the wastewater all winter and do not live in a frost basin, the risk of freezing is very small. In this regard, the worst are root treatment plants, earth filters and other extensive methods of water purification, where the purification takes place very slowly and the wastewater spends days in the cold earth.
Objects that are not used in winter, or used only occasionally, are also a problem. There, freezing can occur relatively easily, and it is necessary to carry out perfect insulation of the tanks, drain the system or other anti-freezing measures before continuous frosts, ideally during the last visit to the building. Many of them hide other risks, so choosing an appropriate measure can be quite a challenge.
Freezing can also occur on a smaller scale, with the formation of ice chips and frost, especially in places where water is splashed or otherwise comes into contact with cold air over a larger area. Ice fragments are dangerous mainly mechanically, there is a risk of
- clogging of thin pipes
- puncture of rubber or thin walls (e.g. aeration elements, hoses with air supply, membranes)
- freezing and immobilization of moving parts (primarily biodisc cleaners)
In the winter season, it is usually necessary to drain the outdoor hoses and utility water pipes, which are used for washing and cleaning the walls of the treatment plant. In most cases, it is not possible to wash the treatment plants in winter. This is not a tragedy, but it is good to expect it.
Reduced bacterial activity
Wastewater treatment is always (partially) a matter of billions of beneficial bacteria that break down pollution into harmless or at least less harmful products. Whether these bacteria live in clusters inside flakes of activated sludge, or live grown on plant roots or on the grains of a gravel bed, their temperature optimum will be around 20 °C. As the temperature decreases, the speed of their metabolism decreases until it stops completely at a certain limit temperature. The most susceptible in this regard are the so-called nitrifying bacteria, which are responsible for the conversion of ammoniacal nitrogen. They stop working already at about 8 °C. This is bad news especially for those who discharge wastewater into groundwater (soaking) and therefore have limited concentrations of ammoniacal nitrogen in the discharge.
Reduced activity has its positives, however, bacteria not only eat less, but also grow less, so you won't have to drain the activation treatment plant as much.
Do you dispose of your excess sludge by composting in your garden? It will not compost very well in winter for the same reason.
Impaired access to the treatment plant
In winter it can also happen that snow falls. Do you have a shovel and rake ready? Will a large truck come to your septic tank in the winter to remove its contents? If not, it needs to be exported. It is also advisable to repair all defects that there was no time for during the year. It will go badly in the cold and wet with fragile fingers.