Rinse wastewater treatment
The rinsing wastewater treatment refers to the treatment of wastewater from the filter rinsing. In drinking water treatment, it increases the efficiency of the treatment in order to bring more drinking water into the network. In the swimming pool it is to reduce operating costs utilized
Rinse wastewater treatment in the swimming pool
The requirements for rinsing wastewater treatment in swimming pools are made by DIN 19645: 2016 "Treatment of rinsing wastewater from systems for treating swimming pool and bathing pool water". There three different possible uses for the treated rinse wastewater are shown:
- Type 1: Water for use as filling water, filter rinsing water and applications according to type 2 and type 3
- Type 2: Water used for cleaning surfaces, flushing toilets , and watering outdoor facilities
- Type 3: Water for direct discharge into a body of water
Type 1: Rinse wastewater treatment with ultrafiltration and reverse osmosis
The rinsing wastewater from the bath water filters with the dirt load from the filter rinsing is treated by a rinsing wastewater treatment in accordance with DIN 19645 to such an extent that it is suitable for reuse as fill water. The treated water corresponds to the guidelines of DIN 19643 for fill water. The dirt load is retained in approx. 10% of the treated water volume and fed into the sewer system or further treatment stages. The pollution load depends on the pollution and the treatment method of the pool water circuits. The concentrate of the reverse osmosis contains the concentrated water contents (about 95%) in 20% of the treated water and the quantity is drains supplied. The rinsing wastewater from the pool water filter is collected in the rinsing wastewater storage tank and then goes through the following cleaning stages:
Flushing wastewater storage tank
The rinsing waste water storage tank serves as a storage container for the rinsing waste water treatment. The rinsing waste water is removed from the container via a surface suction system. Depending on the design of the system, the withdrawal of the water begins immediately or after a defined settling time after the flushing waste water storage tank has been filled. The supply pump is switched on and off depending on the level, whereby a throughput that is as constant as possible should be maintained. The sludge contained in the filter backwash water is partially deposited in the rinsing waste water tank. This must therefore be cleaned during the revision , if necessary beforehand, depending on the sedimentation behavior.
Pre-filter
The pre-filter is purely a protective filter and is used only to separate coarse impurities such as hair, plasters, fibers, etc. These impurities can impair the function of the membrane system. The pre-filter is flushed back time-dependently by the automatic processing system.
Ultrafiltration
The ultrafiltration membranes are filled with filter backwash water. The ultrafiltrate is fed to the intermediate container. The wastewater from the backwashes is either knocked off into the sewer or returned to the sludge water tank. After a set operating time, the module or modules are flushed back one after the other with permeate from the intermediate container or subjected to chemical cleaning in which chlorine is usually added to the flushing water via a metering pump . The resulting rinsing waste water is fed into the sewer or returned to the sludge water tank. Ultrafiltration membranes in PVC pressure pipes as capillary membranes made of polyethersulfone .
- Inner capillary diameter 0.8 - 1.5 mm
- Pore size <0.05 µm
- Separation limit membrane <100,000 g / mol
- Resistance to chlorine min. 200 ppm
- Total resistance to chlorine min. 200,000 ppmh
Cache
The filtrate from the ultrafiltration reaches the intermediate container. The container is designed with a closed construction in order to avoid contamination by emissions. The intermediate tank has two tasks: it stores the rinsing water required for backwashing the ultrafiltration and it serves as a water reserve for reverse osmosis. Due to the hydraulic separation caused by the intermediate tank, ultrafiltration and reverse osmosis can process independently of each other. The reverse osmosis system is fed with the water from this container via the feed pump.
Activated carbon filter
A certain amount of chlorine is added to the filtrate from the ultrafiltration to avoid the formation of nuclei in the intermediate container. Since the reverse osmosis membranes are not resistant to chlorine, the free chlorine must be broken down before it enters the reverse osmosis system. This is done through the activated carbon filter. The activated carbon filter is also used in this context, the adsorption of combined chlorine and other adsorbable materials.
UV disinfection
In order to prevent biofouling on the reverse osmosis membrane, the filtrate after the activated carbon filter is sterilized by UV radiation for safety. The filtrate from the ultrafiltration is absolutely sterile. The UV system only serves as a safety device for reverse osmosis.
Antiscalant dosage
The removal of salts and hardness from the permeate makes it necessary to dose antiscalant to avoid scaling on the reverse osmosis membrane. Blocking of the membranes can thus be reduced.
Reverse osmosis
By reusing the treated filter backwash water, the concentration of chlorides, sulfates, nitrates and other salts in the pool water would increase over time. The maximum concentration is limited and removal by means of reverse osmosis is therefore necessary. The filtrate from the ultrafiltration is desalinated and softened by reverse osmosis . The permeate from the reverse osmosis arrives via the buffer tank in the surge water tank of the pool water treatment. The distribution of the added quantities in the respective splash water tank is level-dependent. The concentrate from the reverse osmosis enters the sewer. The reverse osmosis has a bypass line, which enables the filter backwash water to be processed without desalination for maintenance purposes.
Hardening
In order to be able to comply with the minimum acid capacity required by DIN 19643 (KS4.3 = 0.7 or 0.3 mol / m³), the water is hardened. This can e.g. B. done with sodium hydrogen carbonate .
Pure water buffer tank
The permeate from reverse osmosis is temporarily stored in the pure water buffer tank. A low chlorine content is added to the water in order to prevent re-germination.
Distribution pump
The distribution pump feeds the distribution lines to the individual raw water storage tanks in the various circuits.
water meter
According to DIN 19643, at least 30 liters of fresh water must be added per swimmer. In order to document the addition of the corresponding quantities, water meters should be provided in the distribution lines to the individual pool circuits .
literature
- DIN 19645: 2006 "Treatment of rinsing wastewater from systems for the treatment of swimming and bathing pool water", Beuth-Verlag