ES&E Sept09_4:2009 22/09/09 11:10 PM Page 60
Wastewater at its wastewater treatment plants by 2015.” Every municipal wastewater treatment plant is potentially a ‘phosphorus mine’. Agricultural and industrial waste streams are also potential ‘mines’. In Canada and the US, there are moves to recover phosphorus from wastewater. The City of Edmonton, Alberta, and Clean Water Services of Portland, Oregon, have both commissioned plants
If all of the phosphorus available in sewage sludge in the EU was recycled, this could provide 28% of the EU’s total phosphorus requirements. Sweden, for example, has mandated that “ 60% of phosphorus must be recovered at its wastewater treatment plants by 2015.” from Ostara Nutrient Recovery Technologies which recover phosphorus as the slow release fertilizer, struvite. Phosphorus ‘mining’ could even start further up the wastewater chain, with source separation. Urine accounts for only 1% of the total volume of wastewater, but it contains up to 80% of all the nutrients. If it is processed separately, wastewater treatment plants can be reduced in size, water protection can be improved, and nutrients can be recycled. The Europeans are certainly leading
Figure 1. Phosphorus production: When will it peak? (Source: whyfiles.org)
the way in this area. In Switzerland, trials with NoMix toilets have been quite successful; apparently the majority of the Swiss people interviewed said they had no problem with it. Developing technologies There are a number of companies which are developing technologies to extract phosphorus and produce fertilizer products: 1. Phosphorus recovery from sludge and sludge ash - When sewage sludge is incinerated, the resultant ash which is produced can contain high concentrations of phosphorus, more than 10% by weight. Three processes which are being developed to try and recover phosphorus from sewage sludge ash are the Kemira, Seaborne and Sephos processes. There have been pilot plant installations for all three processes. 2. Phosphorus recovery as struvite from sludge side streams - Struvite is the common name for magnesium ammonium phosphate (MAP). Struvite can form naturally where it is least wanted and can cause problems in valves, pumps,
pipes and digesters. However, if it can be extracted from sludge dewatering liquors, it can provide a valuable, slow-release fertilizer product. This has led to the development of a number of fluidized bed reactor technologies to bring about struvite precipitation under controlled conditions and produce a pelletised fertilizer product. This helps to remove nutrients from wastewater, but, rather than a waste sludge, it produces a value-added product. Examples of this technology are the Phosnix process, developed in Japan, the DHV Crystallactor process from DHV/ ProCorp, and the Ostara process from Ostara Nutrient Recovery Technologies of Vancouver, British Columbia. Paul O’Callaghan is the founding CEO of O 2 Environmental. E-mail: paul.ocallaghan@o2env.com. Some of the material for this article was also published in O2Environmental’s book ‘Water Technology Markets – Key Opportunities and Emerging Trends’.
An element with an illustrious history The word phosphorus comes from the Greek word “phosphoros” which means to “have light”. The element was first discovered in 1669 by Henning Brandt, a medieval alchemist from Hamburg, who first isolated it in pure form by extracting it from horse’s urine while in search of the “Philosopher’s Stone”. Later on, thermal treatment of bones from animals was used for phosphorus production. In the 1850s it started to be mined, and, indeed, there was the equivalent of a “gold rush” to Florida around that time as phosphorus reserves were discovered. Later it was used in matches (‘luciphers’) and explosives, and, post World War II, its use in both pesticides and fertilizers has been hugely important in increasing global agricultural output.
60 | September 2009
Environmental Science & Engineering Magazine