Text written in Basque and translated automatically by Elia without any subsequent editing. SEE ORIGINAL

BIDATEK sewage treatment plant for sewage treatment of worms

It is a company from San Sebastian that is implementing a new concept of biological purification plants. In this treatment plant they treat organic pollution; the main novelty is that they transform it into a useful product, that is, they transform it into humus. For this, they use worms and bacteria.

The cow and the worm. Apparently, two animals don't have much to do with each other. However, in the dirty water purification system built by a company in San Sebastián, what is "dirty" by the largest is cleaned by the smallest. And even an even smaller creature participates in the process, the bacteria.

ASIER GUTIERREZ, Bidat "It's
a filter, a filter, a filter made up of different layers. Water is poured from above to pass through the filter. There is a biomass made up of worms and bacteria, and finally the clean water comes out from below and makes humus above."

The biological purification plant based on the bidatek system is being built in the Iztueta dairy in Lazkao. This pool will be filled with layers of sawdust of different granulometry. Depending on the pollution and amount of wastewater, the structure of the layers varies. A customer, a filter. At the bottom, stones or pieces of plastic are always placed so that the water, once washed, continues to the river. On the surface, the biomass of worms and bacteria. The biomass itself is also adapted to organic pollution. Here, the wastewater that they produce during the production of cow's milk is to be cleaned.

ASIER GUTIERREZ, Bidatek "The waters
that we have to treat here are the waters of milk, so we prepare the worms and the biomass for that: we inoculate them and feed them with lactose protein so that later they clean the water and make it faster to the system."

MARY JESUS PRUNING, THE STUCCO
FARM" In short, we transform the milk, and this transformation presupposes that everything must be purified afterwards. There will be 1500 to 2000 liters of water per week to be cleaned."

The Alkiza water treatment plant has been operating since last May. In this case, the wastewater of 350 inhabitants is treated. They come through this pipe. First the solids are removed from the water in this machine and then spread over the filter.

ASIER GUTIERREZ, Bidatek"This is
the automatic control panel of the system; it controls the dispersion of water in the main tank. It is dispersed in the filter by means of sprayers. It is very important for it to work well in the system, because the filter has to absorb everything little by little without making a puddle. If a well were made, the worms would die, the water would not be purified well and we would have poor results."

This process is automatic and the pumps are pre-programmed. In this case, the irrigation is repeated 60 times a day to treat the water of the day. it’s 35 to 40 cubic meters that are cleaned for now. The purification capacity of the Alciza system is up to 60 cubic meters. Until now they have adapted with the septic well, but when it became small and obsolete, they began to study other ways until Bidat came across the system.

JON ROTETA, Mayor of Alkiza"Previously
we had another project to install a different treatment plant. But the expenses went up, and we began to see what could be done. In the end, at the time of doing this, it is not more expensive than the other projects and it also has almost no maintenance costs. The City Clerk is only here 14 hours a month."

Poor maintenance is one of the peculiarities of this system. Simply clean the sprinklers and check if a puddle is made on the top of the filter. It is enough to overturn the earth from time to time. Once a year, the result of the digestion of worms, the humus, must be extracted. To do this, they close one of the sprinklers. As the environment dries, the worms leave: this part is then emptied and the layers are rearranged to finish.

ASIER GUTIERREZ, Bidatek"The worms
will be down now, because it has rained; they like the humidity, not the wells. Worms are the most curious and at the same time the most important element of this system. How are they maintained? The system is very robust, when there is a lot of pollution the worm population goes up and the basal pollution goes down, this population stays."

BORJA VALLINA, Bidatek"This plant
closes the treatment cycle because, in addition to washing the water, it converts the pollution into fertilizer. It does not generate sludge, so there is no cost to treat this water. The expense in electricity is also trivial, and we do not use chemical or biological reagents. It's a cheap system."

In case of looking for disadvantages, of the measure. The filter requires a large amount of ground if the amount of waste water is large. For this reason, it is not viable for large cities. the small town of about 1,000 inhabitants, or the one that is most suitable for the needs of the industry that produces water contaminated with organic matter in its exploitation: nurseries, slaughterhouses, butchery companies or the dairy industry, as in this case of Lazkao.

MARIA JESUS INTXAUSTI, Esttueta farmhouse"We have seen different
systems, but in almost all of them it is necessary to dispose of chemical products to carry out this process. The worm system, on the other hand, does not need any of this; it works cleanly, ecologically."

The purified water is poured into a stream below, after the necessary measurements have been made to ensure that it is truly clean. In these tests, they speed up the process that takes place in the system through the use of reagents. We can find out the degree of organic contamination of water with the help of oxygen.

ARANTXA ABAD, Environmental Engineer"Oxygen
has this capability. He degrades the pollution. Here in our system, the bacteria do it, but we do a chemical process to make the measurement. With oxygen, how much oxygen the sample consumes to degrade it."

The chemical oxygen demand or COD is measured in milligrams per liter. The photometer says how much. The incoming water contains 720 milligrams of organic matter per liter. Once the filter has done its job, the result is different.

Environmental Engineer
"This is the COD of the water coming out, 81, below the 125 mg/l required by law."

ASIER GUTIERREZ, Bidatek "This is
the one who enters, and this is the one who exits, fully useful to throw to a stream or to the ground."