Abstract
This research emphasizes on the utilization of Sewage Treatment Plant (STP) sludge, which is an inexpensive and easily available raw material and a good source for growth of microorganisms because it has enough nutrients and trace elements. This can be considered as an alternative cost effective solution for waste management in addition to the production of a value added product citric acid, one of the important chemicals used in various industrial processes. The isolation of filamentous fungi especially Aspergillus was made from STP sludge for better adaptability. Six strains of Aspergillus were isolated from STP sludge and identified using slide culture technique followed by image analysis. Four strains (SC906, A103, A2017 and A1020) were selected from lab stock. All strains were screened under controlled fermentation conditions such as pH range of 2-3, temperature 30°C and agitation 150 rpm, using 1% (w/w) of substrate (STP sludge), 2% (w/w) co-substrate (wheat flour) with inoculum’s size of 2% (spore mL?1), using a liquid state fermentation process for the maximum production of citric acid. Evaluation of fungal potentiality was done in terms of maximum citric acid production, biosolids production (TSS %) and Chemical Oxygen Demand (COD) removal. Strain A-SS106 produced the highest concentration of citric acid (0.14 g L?1), TSS (15.18 g L?1) and COD removal (90.1%) on the fourth day of fermentation.
Highlights
Sewage Treatment Plant (STP) sludge is one of the final products for the treatment of sewage at a sewage treatment plant
Six strains of filamentous fungi - A-SS101, ASS102, A-SS104, A-SS105, A-SS106 and A-SS107 (Fig. 1)) - were isolated from STP sludge and identified tentatively as Aspergillus by micro-morphological studies using slide culture technique[17] and by examining the size, shape arrangement and development of conidiophores and phialospores with Image Analysis System (IAS) (Fig. 2)
The filtrate was used as inoculum after measuring its concentration by Screening: Screening was done to get the best strain based on maximum citric acid production, treated biosolids and Chemical Oxygen Demand (COD) removal
Summary
STP sludge is one of the final products for the treatment of sewage at a sewage (wastewater) treatment plant. In Malaysia, approximately 3.8 million cubic meters of STP sludge are produced by Indah Water Konsortium (IWK) annually and the total cost of managing was estimated as RM 1 billion[5]. This sludge volume is expected to rise to 7 million cubic meters by the year 2020. STP sludge can be a very good source of carbon, nitrogen, phosphorus and other nutrients for many microbial processes that can add to the value of sludge by producing valuable metabolic products like citric acid. This study emphasized on utilization of a new substrate, sewage treatment plant sludge (STP sludge) for the production of citric acid as well as removal of COD. Applied Sci., 2 (8): 1236-1239, 2005 for better adaptability and its screening for effective bioconversion of the sludge into citric acid
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