Thesis for Master of Science
«Recycling
of olive mill wastewaters as organic fertilizer by the use of superabsorbent
polymers »
MSc.
in Biotechnology (Biochemical Engineering), IST, 2002-05-18
Supervisor:
S.
Martins-Dias
The treatment of agro-industrial effluents using super absorbent polymers is a
patented process by IST/Stockhausen. This thesis considers in particular those
produced by the olive oil industry.
The best super absorbent polymer for application on the soil in combination with olive mill wastewater was selected from a variety of such polymers by studying the effect of various parameters on their absorption capacities. The absorption in equilibrium was studied for water and solutions of varying concentrations of sodium chloride, potassium chloride, caffeic acid, cumaric acid, syringic acid and ferulic acid; a double exponential dependence on concentration was obtained.
The olive mill wastewater was characterised and the effect of its organic content, salinity, and pH on the absorption capacity of the super absorbent polymers was studied. The alterations in its physical and chemical properties after the absorption process were analysed and interpreted. To better understand the behaviour of the saturated polymer, the diffusion of phenolic acids retained in the polymer mesh into an external medium was studied and polymers containing solutions of wastewater were used as a germination medium for plants of the type Rorippa nasturtium-aquaticum, the phytotoxicity being evaluated from the percentage inhibition of the plant growth. Solutions of caffeic acid were inoculated with samples collected from the plant cultures and the degradation kinetics was studied.
Fungi were isolated and characterised by inoculating a specialised growth medium
with particles of super absorbent polymer containing wastewater, used in the
plant growth medium. Penicillium and Aspergillus were successfully
identified.
Keywords:
Olive
mill wastewaters, Superabsorbent polymers, Absorption, Phenolic acids,
Phytotoxicity, Biofertilizer