Stamm, Nadine: Nutrient recycling from animal slurries : Solutions for minimizing eutrophication and environmental pollution. - Bonn, 2013. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
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author = {{Nadine Stamm}},
title = {Nutrient recycling from animal slurries : Solutions for minimizing eutrophication and environmental pollution},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2013,
month = nov,

note = {Economic development with a concomitant higher income as in China is often associated with a growing demand for protein rich food. This has led to high animal densities, especially large pig farms and consequently vast amounts of manure in peri-urban areas in China. As arable land available for direct manure application is limited, this leads to high nutrient (nitrogen (N), phosphate (P)) overloads. Leaching, direct discharge, and gaseous emissions from animal husbandry thus contribute finally to eutrophication of water bodies.
The present work focuses on the recycling of nutrients as a measure to minimize environmental pollution. The objective in this context was to test different techniques for the elimination of N and P from effluents of animal husbandry. The research focused on i) precipitation experiments for phosphate recovery in the form of struvite (MgNH4PO4), ii) the development of an ammonia stripping device consisting of rotating discs and iii) the identification of parameters influencing both processes most. P removal from effluents was assessed by comparing soluble Pi-concentrations before and after different treatments. In a comparison of different methods, I found that the monovanadate-yellow method tended to sometimes grossly overestimate P levels, whereas the molybdenum-blue method was superior. i) Struvite precipitation in slurry or digestate samples was assessed by adding MgO at different molar ratios (Mg:P as 1:1 and 2:1). The PO4-P concentration decreased significantly by around 80% in slurry as well as digestate samples through struvite precipitation. Struvite was identified via X-ray diffractometry. ii) Ammonia stripping was successfully carried out with a rotating disc system. Different surface areas (0.14 m2, 0.28 m2, 0.57 m2 and 1 m2), performed by varying numbers of discs, were rotated through containers with acid and digestate. Ammonium nitrogen (NH4-N) removal efficiencies of up to 85% could be obtained within 4 days. iii) A higher surface area, achieved by more discs in the system or an increased rotating speed removed a higher percentage of the NH4-N in a shorter time. However, an increased temperature did not affect ammonia stripping. Organic matter and suspended solids in the samples influenced struvite precipitation most.
The pretreatment (chemical oxidation) released large quantities of bound P, which could then be precipitated. Struvite precipitation was neither influenced significantly by an increased pH nor by an increased molar Mg:P ratio. During anaerobic digestion, large quantities of struvite precipitated spontaneously in the digester, thus reducing the PO4-P concentration in the digestate. The main conclusions drawn from this research showed a huge N and P recovery potential through struvite precipitation and ammonia stripping in these particular slurry and digestate samples. The removal and subsequent conversion into a transportable form facilitates the nutrient export and redistribution to areas with nutrient shortages. This can thus help to reduce the threat on the environment in peri-urban areas.},

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