Phosphorus recovery from digested sewage sludge as MAP by the help of metal ion separation

This study was designed to solve metal ion influence problem on phosphorus recovery from digested sewage sludge as MAP. The experimental steps were proceeded to maximize MAP production and its quality. Used experimental steps were:

(a)

Acidic dissolution of phosphorus,

(b)

Removal of metal ions from phosphorus rich water phase,

(c)

Recovery of phosphorus as MAP,

(d)

Separation of MAP.

All digested sewage sludge samples were taken from Stuttgart University sewage treatment plant for research and education (LFKW). Four different forms of LFKW digested sewage sludge were used as feeding sample. These were: original digested sludge, diluted digested sludge, centrifuged digested sludge and incinerated digested sludge.A Donnan membrane unit having a Nafion 117 (DuPont) cation exchange membrane was used to remove metal ions from the samples used. Highest metal ion removal efficiencies, which were 98%, 97%, and 80% for Al, Ca and Fe ions, respectively, were obtained from incinerated digested sludge run.Incinerated digested sludge run was used as preliminary step for MAP production and high quality MAP was produced. Produced MAP fulfils all requirements related with Düngemittelverordnung 2003 and it could be used as a fertilizer in Germany.     

Charcoal addition to soils in NE England: a carbon sink with environmental co-benefits?

Interest in the application of biochar (charcoal produced during the pyrolysis of biomass) to agricultural land is increasing across the world, recognised as a potential way to capture and store atmospheric carbon. Its interest is heightened by its potential co-benefits for soil quality and fertility. The majority of research has however been undertaken in tropical rather than temperate regions. This study assessed the potential for lump-wood charcoal addition (as a substitute for biochar) to soil types which are typically under arable and forest land-use in North East England. The study was undertaken over a 28 week period and found:

i)

No significant difference in net ecosystem respiration (NER) between soils containing charcoal and those without, other than in week 1 of the trial.

ii)

A significantly higher dissolved organic carbon (DOC) flux from soils containing large amounts of charcoal than from those untreated, when planted with ryegrass.

iii)

That when increased respiration or DOC loss did occur, neither was sufficiently large to alter the carbon sink benefits of charcoal application.

iv)

That charcoal incorporation resulted in a significantly lower nitrate flux in soil leachate from mineral soils.

v)

That charcoal incorporation caused significant increases in soil pH, from 6.98 to 7.22 on bare arable soils when 87,500 kg charcoal/ha was applied.

Consideration of both the carbon sink and environmental benefits observed here suggests that charcoal application to temperate soils typical of North East England should be considered as a method of carbon sequestration. Before large scale land application is encouraged, further large scale trials should be undertaken to confirm the positive results of this research.