Phosphorus from sewage

Fig. 5.10 Relationship between dissolved ion concentration and river discharge in the River Yare (Norfolk, UK). Direct discharges of phosphorus from sewage and products of weathering (HCOy and Na+) decline in concentration (are diluted) as discharge increases. By contrast, heavy rainfall leaches NO from soil, causing NO concentrations to rise as discharge increases. After Edwards (1973).

Eutrophication The release of nutrients, mainly nitrogen and phosphorus, from sewage outlets and fertilised farmland causes nutrient enrichment. This results in an altered species composition in nutrient-poor habitats and in algal blooms in water bodies, causing a lack of oxygen and fish death... 

As the most significant point sources of phosphorus are those from sewage treatment works (STW), control of phosphorus loading is most readily achieved either by precipitation of phosphorus with iron salts (iron(lll) sulfate or iron(lll) chloride) or by biological removal. The latter can only effectively be achieved in STWs using activated sludge and there have been many descriptions of this technique. ... 

M. Streichan, J. R. Golecki and G. Schon (1990). Polyphosphate-accumulating bacteria from sewage plant with different processes of biological phosphorus removal. FEMS Microbiol. Ecol., 73, 113-124. 

On the other hand, polyphosphates from detergents greatly increase the quantity of food-derived phosphorus that reaches the sewers and sewage works. In fact, 25% of the phosphorus in sewage water originates from detergents, and 75% from toilet waste (Kirchman 1998). 

Even from such a brief overview of its chemistry, it should be clear that phosphorus is an element still at the forefront of all areas of practical chemistry - from purely academic right to decidedly industrial. Though many of the latter uses are declining because of environmental concerns - witness the decrease in the use of phosphate detergents, ZDDP oil additives and organophosphorus pesticides - the fact remains that demand for the element is still enormous. Eventually, as the twenty-first century progresses, this demand will impact upon resources, and economics will dictate that phosphate recovery, - for example, from sewage - becomes vital. Much work to this end is already underway. ... 

Streichan, M., Golecki, J.R. and Shon, G. (1990) Polyphosphate-accumulating bacteria from sewage plants with different processes for biological phosphorus removal. FEMS Microbial Ecology 73, 1 13-124. 

Schaum, C., Cornel, P., and Jardin, N. (2005). Possibilities for a phosphorus recovery from sewage sludge ash. In Proceedings Conference on the Management of Residues Emanating from Water and Wastewater Treatment, Johannesburg, South Africa, Aug. 9-12, 2005. 

Smirnova et al. [5] have described a simple non-enzymatic method of quantitative determination of adenosine triphosphate in activated sludge from aeration tanks. Extraction of the nucleotides in boiling distilled water was followed by removal of the protein impurities by acidification. Barium salts of di- and triphosphates of the nucleotides were precipitated and the precipitate was washed and dissolved in acid to convert the barium salts to sodium salts. The quantity of adenosine triphosphate was determined quantitatively by inorganic phosphorus in the liquid over the precipitate before and after acid hydrolysis, and by ultraviolet absorption spectra. The method was tested in activated sludge from operational sewage works. There was good agreement between the adenosine triphosphate content determined spectrophotometrically and by phosphorus, despite the presence of small quantities of secondary impurities. 

Under normal circumstances, the eutrophication of a lake or pond is a very slow process, requiring hundreds or thousands of years. That rate may he altered, however, hy human activities. For example, runoff from farmlands, municipal sewage, and industrial wastes may contain compounds of phosphorus. When these materials empty into a lake or pond, they may dramatically increase the amount of phosphorus present and, hence, the rate at which eutrophication occurs. It is not unusual today for anthropogenic sources to be responsible for at least 90 percent of all the phosphorus found in a body of water. Under these circumstances, eutrophication may occur in a fraction of the normal time. 

Nitrates and particularly phosphorus remain unacceptably high in Australia. Sedimentation constitutes a problem in both Australia and New Zealand, with the situation improving due to the removal of sheep from steep pastures. Sewage pollution has also been reduced because of the construction of sewage treatment plants. 

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