ABSTRACT
Acidification was used to dissolve phosphorus from digested and non-digested sludge from five wastewater treatment plants in order to make phosphorus accessible for subsequent recovery. More phosphorus was dissolved from digested sludge (up to 80%), with respect to non-digested sludge (â¼25%) and the highest release was observed at pH 2. The acid consumption for digested sludge was higher than for non-digested sludge due to the presence of the bicarbonate buffer system, thus CO2 stripping increased the acid consumption. In all the experiments, the sludge was exposed to acid for 1â¯h. For the five tested sludge types, 60-100â¯mmol o-P was released per added mol H2SO4. It was mainly iron and calcium compounds that accounts for the phosphorus release at low pH. The release of heavy metals was in general low (<30%) for all the wastewater treatment plant, as Zn, Cd and Ni showed the most critical release after acidification of non-digested sludge.
Subject(s)
Metals, Heavy , Sewage , Hydrogen-Ion Concentration , Iron , PhosphorusABSTRACT
Galdieria sulphuraria 074G (Rhodophyta) was grown heterotrophically in defined medium and on amylolytic and proteolytic hydrolysed food waste from restaurants and bakeries. Substrate uptake, growth, and phycocyanin content were quantified in the cultures. The alga utilised carbohydrates and amino acids from the waste but ammonium and other inorganic nutrients were needed to stimulate phycocyanin synthesis. Highest specific phycocyanin contents (20-22mgg-1) were observed in cells grown at 25°C or 34°C on the food wastes. Growth inhibition was observed when the hydrolysates were used in quantities resulting in glucose concentrations of 10 and 50gL-1 for bakery and restaurant waste, respectively. Still, G. sulphuraria 074G grew and produced phycocyanin efficiently on food waste under adequate conditions and may potentially be utilised for synthesise of high-valuable products from food waste.
