Biosolids Management

Sludge refers to the residual, semi-solid material left from industrial wastewater, or sewage treatment processes. When fresh sewage or wastewater is added to a settling tank, approximately 50% of the suspended solid matter will settle out. This collection of solids is known as raw sludge or primary. Commonly with domestic sewage, the sludge is continuously extracted from the clarifier tank for dewatering and disposal. The term biosolids was formally created in 1991 to differentiate raw, untreated sewage sludge from treated and tested sewage sludge that can legally be utilized as soil amendment and fertilizer.

Sludge challenges

The sludge generated from tertiary treatment of waste activated sludge, has been in use in UK, Ireland and European agriculture for more than 80 years, though there is increasing pressure to stop the practice of land application. In the 1990s there was pressure in some European countries to ban the use of sewage sludge as a fertilizer. Switzerland, Sweden, Austria, and others introduced a ban. So, long term uncertainty surrounds the recycling of sludge to agriculture as this the predominant outlet for sludge/biosolids. Many farmers/land owners have for a long time been open to the practice to reduce cost of fertilizing lands with chemical fertilisers.  However the risks of spreading sludges and biosolids to agricultural land which is producing food or animal feed is starting to come to the fore. 

Resource Recovery

Plant nutrients in wastewater sludge represent both a valuable resource and a major environmental problem. Efficient and safe recycling of these nutrient flows is a major bottleneck in building sustainable societies and healthy environments. BioCore has identified a unique technology that can solve the problem of resource recovery from various waste streams through volume reduction, removal of solids, and the concentration of plant nutrient recourses. 

The recycling potential of plant nutrients in these organic waste streams is often limited due to high water content and low nutrient concentration, leading to higher handling costs than for mineral fertilizers, or because of contamination with heavy metals or other toxic substances. Separating and concentrating plant nutrients from these waste streams will increase the safe re-use of valuable resources and at the same time reduce environmental impacts of waste disposal.  This unique technology processes organic wastes into three fractions: 

- a solid organic fraction

- a liquid nutrient concentration (A significant percentage can be brought to a commercial grade/standard)

- and water (Which meets a stringent groundwater release standard). 

Sludge as an Energy source

Did you know that the solid fraction of sewage sludge contains more energy than is needed to treat it? On average, dried sewage sludge contains as much energy - kilo for kilo - as lignite coal. Therefore, it makes sense to use the available energy in sewage sludge and to recover the energy from the sewage sludge as a refuse derived fuel. As renewable energy, sewage sludge can be integrated into wastewater treatment systems which can make wastewater treatment plants net exporters of renewable energy - instead of net importers of fossil fuel based power from the grid. The more sewage sludge that is used as a "fuel" in generating renewable energy, the more that we reduce greenhouse gas emissions. 

BioCore have three primary outlets for energy recovery of the solid fraction:

• Alternative fuels for the cement industry (Co-firing)
• Anaerobic Digestion 
• Mono incineration of sludge

Recycling Biosolids to land (Energy crop facilities)

The facility acts as a very effective and robust biofilter, converting the useful nutrients into wood, which is then harvested for fuel. Controlled irrigation of such liquids on to this non-food crop has the advantage of fertilising the crop to increase fuel yields while at the same time solving an issue for the waste producer.

Correctly operated, there is no outflow to surface or groundwater from the system, making it an ideal way to completely recycle effluents in a sustainable and secure manner. The technology is well established in other EU countries. Working with the EPA, Dept. of Environment and Local Authorities we will continue to raise the standards in the field of BioFiltration.