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• Limiting waste water during the crop rotation
• Handling waste water in a smart way
• Cleaning dripping system without waste water
• Disinfecting the water system
• Cleaning basins and silos

You can limit the quantity of waste water by stopping the water supply in time. As a result the crop will largely absorb the remaining water from the substrate, so the substrate dries up as much as possible. Thus, you can do the following:

• By the end of the cultivation limit the drain quantity and during the last days only pour drain water. This will empty the drain tanks. 
• Make sure that the water content of the substrate is as little as possible, so that during the crop rotation hardly any water can leak from it. 

But even if you do this, there is no way of avoiding waste water. Therefore, it is important that you handle waste water in a smart way. For example, consider the cleaning and disinfection agents that you make use of: will you decide to use chlorine, or choose an eco-friendly alternative that could be reused? And could it be possible to use less agent in certain circumstances? 

Before you start the new cultivation, you want your water supply system to be immaculately clean. For that reason it is recommended to increase the hydrogen peroxide dose during the last weeks of the cultivation to be sure of a clean water supply system. Thoroughly rinse the dripping hoses a few times. There are great solutions for bringing the rinse water from the dripping hoses back into the drain system (for example, via a loop with a valve at the end of the hose, allowing the water to run back into the drain channel). This way all the water is being reused. If possible, have the water in the dripping system checked on germs just before the crop rotation. There are also some pretty neat solutions for proper filtration of drain water, so this can end up (before disinfection) back into the drain system.  

For the disinfection of, for example the drain pit, drain pipes and tanks, chlorine is often used, because of the low costs. The disadvantage of chlorine however, is that it is not really degradable and leaves residual product. Therefore, you might want to consider the use of the much more stable hydrogen peroxide, for example Huwa-San. Its concentration can easily be controlled and due to the high stability you can disinfect multiple sections or silos with one single solution. The advantage is that less product is being consumed and it provides more certainty that proper disinfection takes place in the entire water system. Leave the remainder of the disinfection fluid in a silo until the active substance content has degraded, then no residual materials will be left (whereas in case of chlorine these materials will remain).

Due to weather influences as well as dirt, a layer of sludge can be created in basins and silos. The crop rotation is a particularly suitable time to make sure this is cleaned up. Specialized companies can come and the water in water basins and silos, without the need to take the water out. All water storage can be cleaned again afterwards using Huwa-San. 

Light is of major importance during the new cultivation. For that reason most growers clean the glass during each crop rotation. Usually a product based on fluoride is used for this, but more and more environmental-friendly alternatives are available in the market. For example, recently an ecological glass cleaner was introduced that is fully biodegradable. The possible residue of the product, washed away with the water, are hardly a problem. Presently, this product is also being tested on the safety for Anti Reflection coatings (AR-coatings). 

The cleaning of cultivation gutters is a time-consuming task that creates a lot of waste water, while the final result leaves a lot to be desired. If chlorine is added to the water continuously while cleaning of the gutters, a lot of product is being used which increases the risk of emission. You can do this in a different way by spraying the gutters with an alkali detergent. You allow it to soak and then wash the gutters down. This will reduce the consumption of and product. There are also certain cleaning agents that you can apply as foam, so as to lengthen the soaking time of the product. 

Once the gutters are clean, we strongly recommend working with gutter film. This will keep the gutters much cleaner, while cleaning takes less time and discharging a lot of waste water is prevented. 

Waste water containing fertilizers and/or pesticides, may not be disposed of in the surface water. Therefore, this water must be collected and discharged through the sewer. The following waste water flows may not be discharged into surface water:

• Leachates: if a crop is temporarily stored outdoors, it will digest. In this process leachates are created, containing fertilizers and/or pesticides.
• Runoff water of old substrate mats: even if you stopped the supply of water in time, runoff water will come out of the old substrate mats. This must be discharged through the sewer. If you store this outside in a container, then ensure that the container is covered. This way you prevent rain water from being added, increasing the quantity of runoff water.
• Washing water: when, during cleaning, you make use of cleaning and/or disinfection agents, the water may not be disposed of in the surface water. If you use water only, this is allowed.
• Silo water: when you clean a waste water silo, you must discharge the dirty water into the sewer.
• Runoff water from new substrate mats: if you are going to cut the new substrate mats after filling up by dripping, you must collect the water and discharge it through the sewer. Since a large quantity of water will be released here, you had best cut a little piece of the film and cut it through entirely afterwards. This prevents all the water being released at once, so it is easier to collect it. You can also choose not to drain all substrate mats on the same day, but to dose it. As such, you can use the drain water of the first sections to create the following sections.

You can choose to have the waste water purified. For this, a  mobile purification installation is a good option. Mobile water purification means that you have the residual water flow purified by a service provider that has a mobile water purification installation. This way the water is being purified on location.

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