Assessment of nutritional value of single-cell protein from waste-activated sludge as a protein supplement in poultry feed.
The amount of protein wasted through sludge in Gauteng, South Africa, amounts to 95 000 metric tonne/yr, with the order of magnitude of the national protein requirement of approximately 145 000 metric tonne/yr. Waste-activated sludge (WAS) from wastewater treatment plants (WWTPs) that treat domestic wastewater contains protein in a ratio of 2:1 against fishmeal. This protein source has not been utilized because of the high content of toxic heavy metals and other potential carcinogenic pollutants in the sludge. In this study, a pretreatment method of modified aqua regia dilute acid wash was used to lower the metal content by approximately 60%. However, this resulted in a 33% loss of amino acids in the acid-washed WAS. A feed substitution test in poultry with different fishmeal-sludge ratios (0%, 25%, 50%, 75%, and 100% WAS as percent substitution of fishmeal) showed no impact of sludge single-cell protein (SCP) on mortality rate. However, sludge substitution in the feed yielded weight gains and cost savings up to 46%.
Water Utilisation Division, Department of Chemical Engineering University of Pretoria, Pretoria 0002, South Africa. Evans.Chirwa@up.ac.za
Evans M
EM
Nkhalambayausi-Chirwa
Moses T
MT
Lebitso
D000596:Amino Acids / Q000032:analysis; D000821:Animal Feed; D000818:Animals; D002645:Chickens; D003362:Cost-Benefit Analysis; D004044:Dietary Proteins / Q000008:administration & dosage*; D019587:Dietary Supplements; D019216:Metals, Heavy / Q000032:analysis; D009753:Nutritive Value; D012722:Sewage / Q000032:analysis; D014865:Waste Disposal, Fluid
D000596:Amino Acids; D004044:Dietary Proteins; D019216:Metals, Heavy; D012722:Sewage