Drainage system, disinfection of drainage

Most of the nutrient solution supplied to the plants is absorbed by them. However, for normal growth and functioning of the root system, it is necessary that part of the solution goes into the drainage. The daily amount of drainage can range from 30% to 60% depending on the culture, time of year and other factors. This ensures good moistening of the substrate and the supply of the required amount of nutrients to the plants without salinization. For the correct dosing of the nutrient solution, constant quantitative and qualitative control of the drainage is necessary - it is important to know its quantity, acidity, and the amount of salts dissolved in it. At the same time, with the drainage a lot of water and mineral fertilizers are lost, and the discharge of drainage into the sewers or reservoirs harms the environment and entails heavy fines. Therefore, drainage must be collected and reused. However, the collected drainage contains many mechanical and biological contaminants, so its use without cleaning and disinfection is not permissible. In greenhouses designed by VENLO, we propose to install a system for collecting and recycling drainage. The system allows you to collect, control, filter, disinfect, and reuse drainage without loss. The following is a general description of the drainage collection and recycling system using the example of a greenhouse complex with plants that are grown in a substrate isolated from the soil in drip irrigation.

 

Drainage collection.

On each span of the greenhouse, issues of 50 mm are displayed, connected to drainage pipes of 125 mm, which are enclosed underground along both ends of the gables of each compartment. Drainage pipes are connected by a pipe d.160 mm to an underground airtight drainage well with a capacity of about 1 cubic meter, made of polyethylene or fiberglass, located in the greenhouse along the central path. In the well there is a submersible pump connected through a non-return valve to a pressure pipe of 110 mm. The discharge line is laid from the wells of the tank for a large amount of crude drainage. The volume of the tank allows you to collect and store up to the processing of more than daily drainage volume. Pipelines are completed with manual cranes and connecting fittings. All pipeline parts made of PVC, which, together with the underground laying, guarantees their operation during the whole period of operation of the greenhouse, without maintenance, replacement and repair.

 

Accounting for drainage.

Before entering the tank, drainage passes through flow, temperature, EC and pH sensors. The sensors are connected to a single automation system for the quantitative and qualitative control of drainage and automatic correction of irrigation.

 

Drainage cleaning.

Good pre-filtration is important for further disinfection. Particles contained in water can create a shadow when irradiated and carry pathogens with them. To do this, the kit includes a filter with sand filter deep cleaning. The filter station is fully automatic, with a backwash system, which is activated in time or when the pressure difference between the inlet and outlet. You can read more about filters on the Filtration Systems page.

 

Disinfection of drainage.

There are two main methods of disinfection of drainage - using high temperature and irradiation with hard ultraviolet light (shortwave UV radiation). We supply a UV-C system with a wavelength of 254nm. The range of ultraviolet radiation is divided into four ranges:

  • UV-A (315-400 nm);
  • UV-B (280-315 nm);
  • UV-C (200-280 nm);
  • UV Vacuum (100-200 nm).

The UV-C subrange and part of the UV-B have a disinfecting effect, i.e. radiation with a wavelength of 200 - 320 nm. Ultraviolet radiation disinfection is based on photochemical reactions that cause physicochemical and biological transformations in the living matter of microorganisms (bacteria, viruses, protozoa) - radiation destroys DNA molecules in the cells of bacteria and microorganisms, preventing their reproduction. Intensity, i.e. The radiation dose of the disinfection unit can be selected for the purpose of selective or complete disinfection. With selective disinfection, mold (fungi) and bacteria die. With complete disinfection near the mold and the bacteria are also destroyed by the virus. Radiation dose is the total amount of energy that enters the water in the form of UV radiation.

 

The dose of radiation depends on three factors:

  • The average intensity of irradiation with which water is processed.
  • The residence time of water in the irradiation chamber.
  • The water transmission index T10.Т10 is the percentage of UV-C radiation remaining after the incident through a 10 mm thick layer of water. The lower the value of T10, the more energy is required for the required dose of UV-C. The value of T10 drainage water when grown on a substrate, usually ranges from 20% to 40%. When grown on organic substrates, the transmittance value decreases. To achieve T10 = 20% or higher, it is necessary to add pure water. Dutch experts have determined the minimum dose of radiation needed to prevent plant diseases. In the course of biological experiments, the previously contaminated water was disinfected and supplied to young plants.

At T10 = 20% or higher, the following radiation doses are defined:

For selective disinfection (algae, fungi, bacteria): 100 mJ / cm

For general disinfection (including viruses): 250 mJ / cm

 

Installation work.


The disinfection unit operates in fully automatic mode. When the system according to the level sensors determines that there is enough liquid in the tank with unpurified drainage to operate the installation for at least 2:00, the installation switches to the “start” mode.

 

During start-up, the water from the installation is sent back to the drainage tank until the lamps attain sufficient temperature and the necessary radiation dose is reached, after which the system switches to the tank with disinfectant drainage.

 

Water passes through irradiation chambers along lamps in a turbulent flow. Turbulent flow in combination with a long exposure time (water passes through 6 or more lamps, depending on the model) allows optimal disinfection of drainage water. A UV-C sensor is located on the outer wall of the irradiation chamber, which continuously monitors the radiation. The flow is also controlled, i.e. the amount of water passing through the installation. This ensures optimum performance and disinfection of water from bacteria, fungi and viruses.

 

Powerful PLC-controller with display controls the optimal operation of the entire installation. Also, the processor has an archive of accidents that can be viewed for all the years of the installation. The processor has a lamp operating hours counter, controls acid injection during flushing.

 

After the disinfection cycle, a small amount of acid is automatically injected, so that no precipitate is formed and the quartz tubes in which the lamps are located remain clean until the next disinfection cycle.

 

Subsequently, the disinfected drainage according to the irrigation program is automatically mixed into clean water, then the solution enters the fertilizer dosing unit, and then to the plants. Part of the nutrient solution is absorbed, part falls into the drainage. The cycle repeats.

In ATS-Ukraine you will find everything for drainage , and prices for drainage works will pleasantly surprise you.