Why doesn't the current "septic tank" work?

In the previous agricultural society, people's excrement (commonly known as "water and fertilizer") was an important source of fertilizer, and in order to obtain "comparatively fertile" water and fertilizer, it was necessary to regularly pick out the water and fertilizer, because if the water and fertilizer stayed in the septic tank for too long , it will be slowly decomposed by the microorganisms in the pool! Because water and fertilizer are composed of organic matter, it has been a favorite food of microorganisms since ancient times.

But the strange thing is that no one uses poop to fertilize anymore. Why do water and fertilizer trucks pump water and fertilizer all over the streets and alleys? This is because the current septic tank has long lost its decomposition function, so the pond is easily filled with water and fertilizer, so it is necessary to pump water and fertilizer regularly. Calculated by 100 communities, an average of 2,000 kilograms of water and fertilizer need to be removed a month, which is scary. !

Why is it that the septic tank of the agricultural society can decompose poo, but the high-tech toilet of the 21st century does not? This is because when we design toilets, we only pay attention to people's comfort and freshness, but we forget to leave a suitable environment for the microorganisms in the septic tank to thrive..

The following three details that are often overlooked are the main reasons for the death of microorganisms, which directly lead to the "no" septic tank strike:

The first point: the living environment is dangerous

Originally, the "septic tank" relies on the abundant microbial species in the tank to decompose the sludge, but we use a large amount of chemical agents such as sodium acid (strong acid), pipe cleaner (strong alkali), disinfectant water, detergent to clean the toilet, After these chemicals flow into the septic tank along the drain pipe, the bacteria will be highly inhibited, especially if the concentration is too high, the bacteria will even die out, and the septic tank lacking viable bacteria is at best a large container for feces. The septic function is completely lost. At this time, not only will the septic tank rapidly accumulate "water, fertilizer" and "grease", resulting in a significant increase in the number and quantity of water and fertilizer pumping, and will lead to four major sequelae such as drainage pipes and septic tanks.

The second point: stay for a short time

General microorganisms can be divided into three categories: aerobic, anaerobic and facultative. Aerobic microorganisms, like humans, need to survive in an oxygen environment; for anaerobic microorganisms, oxygen is their poison, as long as they are exposed to When a little oxygen is reached, it will die; the most powerful are facultative microorganisms, which can live freely in an oxygen or anoxic environment. Due to the extreme lack of oxygen in the septic tank, the microorganisms in the tank are mainly anaerobic microorganisms.

For a septic tank to efficiently decompose water and fertilizer, the premise must be that there are enough anaerobic microorganisms in the tank. However, the growth rate of anaerobic microorganisms is extremely slow, and it takes 5-15 days to reproduce a generation. In short, it takes about 10 days for anaerobic bacteria to multiply from 1 to 2, and from 2 to 4, it takes another 10 days, and so on.

In the agricultural era, the population was small and the land area was large, so the bacteria in the pool had enough time to multiply. However, in modern community buildings, there are too many residents, and the septic tank tank is too small. On average, 50 residents (about 150 people) will share a septic tank of 27 cubic meters. Based on the calculation of 250 liters of sewage per person per day, about 38 cubic meters of sewage will flow through the septic tank every day, which means that the sewage will stay in the tank for less than 1 day. Such a short residence time will greatly impact the anaerobic bacteria. reproduction speed.

The third point: oil mixed with water and fertilizer

In the past, only feces would flow into the septic tank, but since 1999, our government has made a strange decision, requiring all new buildings, toilets and kitchen sewage to enter the septic tank first for anaerobic Treatment (that is, the first tank of the "sewage treatment facility"), and then go through aerobic, sedimentation and disinfection in sequence, this seems reasonable, but it has actually been proved to be a wrong policy!

I have seen too many such cases. Originally, the septic tank can still decompose water and fertilizer, but as long as the kitchen sewage flows through the septic tank, the microorganisms in the tank will be dead, because the kitchen sewage contains grease, and grease is a big poison to microorganisms. , because oil will not only encapsulate microorganisms to cause hypoxia and hinder nutrient delivery, but also produce free radicals to attack microorganisms, resulting in a large number of bacterial deaths.

I think the government should just simply want to deal with the kitchen sewage problem (because the kitchen sewage can be directly discharged into the ditch), so it will direct the kitchen sewage into the septic tank, so not only does it not need to add additional treatment equipment, but also Kitchen sewage is rich in organic matter and can also provide more nutrients for microorganisms. Little do they know that oil and fat can cause such a major ecological catastrophe. This policy is really the last straw that broke the septic tank, and Taiwan's septic tank will never be used again. septic.

But also because of this mistake, Taiwan's water and fertilizer industry can flourish. According to ITRI estimates, Taiwan's daily water and fertilizer removal volume exceeds 5,000 metric tons, but in Taiwan, only 5 cities, including Taipei, Hsinchu, Taichung, Tainan, and Kaohsiung, have water and fertilizer treatment plants. The other 18 counties and cities have none at all. Water and fertilizer treatment facilities; and the five water and fertilizer treatment plants in Taiwan only process 890 tons of water and fertilizer every day. In other words, at least about 4,000 tons of water and fertilizer in Taiwan go missing every day. It is reasonable to speculate that most of these 4,000 tons of water and fertilizer are secretly discharged into rivers. Or soil (for more information, please refer to the 4,000 tons of water and fertilizer that flow through Taiwan every day), so how to deal with water and fertilizer more efficiently and environmentally has become an urgent priority!

The oil flows into the septic tank, causing a large number of bacterial deaths (as shown in the figure below). After a long time, the oil and water and fertilizer will combine with each other and harden. In the end, if the water and fertilizer truck cannot be removed, it needs to be excavated manually, and the cost is quite amazing.

Because the septic tank has a lot of food (water and fertilizer), it is warm and humid, so many cockroaches have been hidden in the septic tank, but since the oil was added to the poop war, there have been more cockroaches than before. To be honest, I began to miss the simple hut before. now...