Biosolids Management : A Global Perspective

What better way to learn about biosolids management then to compare our processes and procedures at home to those abroad?

Europe provides an excellent example of biosolids management tactics that are creating results that better the environment and the economy. In fact, the European Union (EU) has committed to treating biosolids as a valuable resource, rather than a burden, as a requirement of long-term sustainability. The EU encourages the use of biosolids for both energy and land application. Currently more than half of the biosolids produced in the EU are used on farmlands. Some of the most active European participants in biosolids management include France, Portugal, Belgium, Italy and Denmark.

In Europe, biosolids are encouraged to be used in the following ways:

  • Agricultural cropland application
  • Commercial sale as fertilizer for horticultural landscaping applications
  • Rangeland and pasture application to improve available grazing
  • Land application in reforested areas

European Union Regulation

In 1986 the EU regulated the use of biosolids for the first time after it was already widely used among agricultural practice in many countries. This regulation set a maximum value of concentrations of heavy metals and bans the spreading of biosolids when the concentration of certain substances in the soil exceeds these values. It also requires Member States to keep records of biosolids use on the following subjects:

  • Quantities of biosolids produced and the quantities supplied for the use in agriculture
  • The composition and properties of the biosolids
  • The types of treatments being carried out
  • The names and locations of recipients of land application

Member States must produce a consolidated report every four years to be published by the Commission, who will, if necessary, submit appropriate proposals for any increased protection of the soil and environment. Other relevant legislative materials include the urban wastewater treatment directive, nitrates directive, water framework directive and the hazardous substances regulations. The quantity and composition of biosolids across Europe have been impacted by these precautionary measures.

By providing a variety of laws and rules that regulate the biosolids management industry, the European Union has been able promote the use of biosolids in a safe and environmentally sustainable way. By constantly updating these regulations based on further scientific discovery and amount of sewage sludge being produced, Europe has been able to successfully minimize sludge in landfills and maximize the use of biosolids in a variety of forms.

In Canada, specifically Ontario, we are still years away from managing and regulating biosolids the same as the European Union. To learn more about Ontario’s ‘Waste Free’ Initiative, check out this blog post or contact us to learn more about your options. The European Union is leading the way and Ontario isn’t far behind.

What is Dewatering?

Dewatering in its simplest definition is the removal of water. This process is used in many industries but commonly referred to in construction and wastewater when water is separated from solids through a variety of different pumping or filtering processes.  Construction dewatering is often referred to as dewatering, unwatering, or water control. It involves pumping from wells or sumps to temporarily lower groundwater levels, to allow excavations to be made in dry and stable conditions below natural groundwater level.

In wastewater treatment, dewatering is the part of the process whereby sludges are reduced in volume and converted from a liquid to a solid product. Biosolids dewatering typically occurs when transportation and storage costs for large volumes can be reduced or when the material is destined for landfill.  The biosolids dewatering  process not only effects the volume but also the nutrient and odour levels of the material.

Dewatering Techniques

  1. Centrifuge: The centrifuge works in a similar nature to a front loading washing machine. The spinning action causes a separation of water from the solids.  This process typically requires a large power input and polymer addition.  The system works best with a consistent slurry or feed sludge and provides a dewatered product between 16-35% solids.
  2. Belt press: If a centrifuge can be compared to a front loading washing machine then the belt press can be compared to a wringer on an old washing machine. The method of separation is primarily obtained by passing a pair of filtering cloths or belts through a system of rollers. The system takes a sludge or slurry as a feed, and separates it into a filtrate and a dewatered product between 12-35% solids.
  3. Geo-textile: High strength permeable fabrics are woven into dewatering bags that can be filled with slurry. The water permeates from the dewatering bag through the small pores in the geo-textiles resulting in effective dewatering and volume reduction of the contained solid material. Although somewhat slower than mechanical dewatering options, geo-textile dewatering is an excellent dewatering option, reducing costs, and energy inputs.  This method can produce material from 15-45% solids.
  4. Rotary Vacuum: This method of dewatering involves the suction of liquid through a filter.  Because the filter itself can be changed depending on the project needs, the solids capture rate is very high. Material can be filtered down to 0.5 micron producing unparalleled effluent quality.  This process while slower than other mechanical dewatering options provides material with 20-45% solids.

Dewatering and Waste Management

Dewatering is used by large wastewater treatment plants to separate sludge into a liquid and solid. The principle methods in wastewater are belt filter presses and centrifuges.These systems are high maintenance and require a high degree of supervision and operator training. They are usually only implemented at larger facilities and are not cost efficient to be used on a small scale. This is only one part of the process of wastewater becoming treated water and biosolids.  Primary treatment is essential prior to the dewatering. The filtrate or centrate liquid which is separated during the dewatering process must also be treated. This typically involves circulation to the headworks of the wastewater treatment plant.

Not sure what the optimal solution is for you? Download the Waste Audit worksheet.

Harvest season is coming, have you considered your soil health?

Harvest season is soon to be upon us in southern Ontario!

Dust will be flying as growers race to harvest their crops at the optimal time. Shortly after harvest, planning and planting for next year will begin. Be sure to consider your soil health when harvesting and planning for next year. There are a number of options available for growers to improve their soil, including:

  • Fertilizer
  • Manure
  • Compost
  • Non Agricultural Source Materials (NASM) such as biosolids

Each nutrient source can help to boost your soil health and can provide unique benefits for your soil and the coming season. Each nutrient source has specific requirements for use under the Nutrient Management Act (NMA) that are important when considering which to use. Check out details for nutrient use here.

Wessuc’s primary recommendation is to pay attention to your manure storage. If your manure storage is filling up again, it should be your primary nutrient source as it also provides a great source of organic matter and micro nutrients to improve your soil health.

If you need help emptying it prior to any fall planting or field preparation contact us, we’d be happy to help with spreading. However, if you aren’t sure which nutrient source works best for you Wessuc can create custom nutrient plans and strategies in time for harvest season. Get started by emailing us at