Nutrients

• Buffer zone
• Catch crop
• Controlled drainage
• Crop rotation
• Drainage cuts
• Gypsum treatment
• Ploughing direction
• Phosphorus precipitation
• Reduced tillage
• Sedimentation pond
• Filter applications
• Structural liming
• Two-Stage drainage
• Wetland

Surface runoff and drainage flow from agricultural fields transports suspended solids and nutrients (nitrogen and phosphorus compounds) into receiving waterbodies. The amount of loading depends on several factors, such as the use of fertilizers, field soil type and nutrient content, sloppiness, vegetation and climate.

Good agricultural practices and use of right load reduction methods can mitigate loading into waterbodies. However, choosing the best water protection measure might be difficult. The decision support tool (Excel) helps you to select suitable methods for your particular field or farming area.

How to use the decision support tool?

The tool contains a set of different load reduction methods and questions that help you to choose an appropriate method for your field. If you wish to reduce the number of optional methods, you may use the filter options in the upper part of the table. For more information on methods of interest, use the links to information sheets in the rightmost column. Note: The decision support tool is only meant to be instructive. The consultation of an expert prior to actions is recommended.

Along with rainwater and run-off water from arable land, phosphorus flows into the waterbody and causes eutrophication in the receiving watershed and eventually in the Baltic Sea, seen as, for example, toxic blue-green algae (cyanobacteria) blooms in the water. One method to reduce dissolved phosphorus inflow is to build affordable small-scale filters in ditches next to arable land. In the project’s pilot watershed of Eurajoki area, new technology has been tested for phosphorus reduction. The working principle and the main steps to build a phosphorus filter are presented in the video.

In Latvian pilot watershed, a calcium hydroxide filter was installed on a small stream as a mean to prevent phosphorus loading to surface waters. In addition, laboratory tests were performed to increase the filter’s water flow capacity.

Phosphorus in surface waters may be particle-bound or in a dissolved form. The latter is practically entirely algal available whereas bioavailability of particle-bound phosphorus may vary upon conditions in the receiving water body. Particle-bound phosphorus can be retained through induced particle sedimentation. The removal of dissolved phosphorus from water, however, needs biological or chemical treatment.

Chemical phosphorus precipitation is a water protection method capable of binding dissolved phosphorus even off the growing season. Applicability of the method to a small size loading hotspot was piloted in the Aurajoki watershed. Phosphorus precipitation with granular ferric sulphate was demonstrated in two agricultural ditches with high dissolved phosphorus concentrations and low discharge. Building of the dosing unit at the demonstration site is illustrated in the presentation available below.

Slide show – How to build a phosphorus precipitation unit for ditch water treatment

For additional information on the method and principles, click here. Additional building instructions are available in Finnish here. Before installation of the phosphorus precipitation unit, please contact an expert and check the national legislation on the subject.

This checklist presents observations and hints for installation and investing of some small scale nutrient removal technologies. If you are more interested in the subject, please check the more detailed version of the list (in English).

This guidance is based on experiences gained during the WaterChain project pilot investment implementation. When implementing any kind of construction or other actions described here, always check for related laws and other regulations. The project is not responsible for any consequences affected by further use of described methods or procedures.

Guidance on investments

Planning of investment

• Planning of devices, technical drawings and construction works should always be carried out by a professional.
• One of the most important tasks is to identify hotspots for phosphorus load when selecting the investment site.
• A suitable method for the phosphorus reduction will be chosen based on the site properties (e.g. soil type).

Permissions needed in installation of filter

• At least the permission from the landowner(s) is needed.
• Specify clearly to the landowner what is happening, when, who is responsible, and how it is going to influence his/her property.
• Make a written agreement on rights and responsibilities between contracting parties and involved stakeholders.

Permissions needed in installation of filter

• At least the permission from the landowner(s) is needed.
• Specify clearly to the landowner what is happening, when, who is responsible, and how it is going to influence his/her property.
• Make a written agreement on rights and responsibilities between contracting parties and involved stakeholders.
• Check also country specific permissions.

Tendering

• If paid excavator services are needed, make at least a price comparison.
• Tendering is necessary, if funding regulations or any related administrative rules require it, or if larger or several applications are constructed.
• Notice that also other possible expert services may require tendering.

Possible expert services

• Contact an expert for optimal site selection and for worksite supervision.
• Excavation works are also commonly done by service providers, but in minor projects it is possible to negotiate with the landowners, if they have their own excavators or other suitable heavy machinery.
• Expert services could be needed also for elevation measurements and for laboratory analysis of water in monitoring the efficiency of the method.

Worksite preparations

• The scheduling of the work and logistics is crucial to minimize stand by hours on the site.
• Worksite has to be accessible to all machinery.
• If additional rock material is needed, suitable areas for unloading cargo must be cleared.

Worksite safety

• Worksite supervision must be conducted by project manager or by expert services.
• Use protective clothing, eyewear and respiratory masks when operating in close contact with calcium hydroxide or ferric sulphate.
• The country specific safety and working instructions and regulations must be taken into account.

Set up facilities for effectivity monitoring

• Monitoring is implemented mostly by taking water samples, but also automatic monitoring is possible.
• Monitoring facilities should be modified based on purpose.
• Sufficient areas for taking water samples should appear right before and after water entering installed device.

Informing of actions

• Inform local stakeholders in person or in larger constructions organize an informative event.
• Attach a notification close to the site describing what is happening and who is conducting actions.

Guidance on maintenance processes

Effectivity monitoring and surveillance

• Monitoring of installed device is a basis for evaluation of phosphorus removal effectivity and usability of piloted methods. Take water samples and analyze them in an accredited laboratory.
• During sampling visits, implement general surveillance of devices and premises.
• Mark the observations in a field diary.
• Combine the collected date-based metadata with water quality results for further effectivity evaluation.
• The cooperation with the landowner(s) considering practical issues is highly important.

Maintenance processes for phosphorus reduction by small scale filters

• Phosphorus reduction filters do not need active maintenance after installation.
• Active operation surveillance of devices has to be proceeded as described in the previous chapter.

Maintenance processes for phosphorus reduction by ferric sulphate application

• Refill the ferric sulphate container regularly.
• A dry storage space for chemicals is needed.
• Check operation of the dosing system once per month at the minimum due to the hygroscopic properties of ferric sulphate and varying environmental circumstances.
• Carry out surveillance of changes in pH values.

After the project

• All installations made for the pilot site should be easy to take down.
• Depending on the future situation, the precipitation unit is usually best to dismantle so there won’t be any remains of possibly harmful chemicals.
• Small scale phosphorus reduction filters could be dismantled by excavator. The filter masses need to be handled properly.