ABSTRACT
Filamentous and nonfilamentous microorganisms can cause bulking and foaming in wastewater sludge settling and dewatering. In this research, sludge degradation and bioflocculation was studied using pellet-forming filamentous fungi isolated from municipal wastewater sludge. To understand the role of filamentous fungi in sludge settling and dewatering, the isolated fungi was inoculated with both spores and pellets (beads) into sterilized and nonsterilized sludge having different suspended-solids concentrations. Biofloc formation, sludge settling, sludge degradation, change in pH of fungal-grown medium, zeta potential, and microscopic analysis of bioflocs were performed. The suspended-solids concentration was found to decrease over 5 d of incubation because of use and biodegradation by fungal biomass. The isolated fungal strain was well adapted to forming biofloc and to interacting with natural microbial flora and exhibited low capillary-suction time for sludge dewatering.
Subject(s)
Fungi/isolation & purification , Sewage/microbiology , Waste Disposal, Fluid/methods , DNA, Fungal/chemistry , DNA, Fungal/genetics , DNA, Ribosomal/chemistry , DNA, Ribosomal/genetics , Flocculation , Fungi/classification , Fungi/genetics , Molecular Sequence Data , Mycelium/genetics , Mycelium/growth & development , Phylogeny , Sequence Analysis, DNAABSTRACT
One of the major problems in overall wastewater treatment process is sludge settling and dewatering. In general, sludge settling and dewatering is carried out using conventional physico-chemical methods that are known to be expensive, and these processes further increase the sludge volume and ultimate disposal costs. To overcome this problem, a suitable alternative could be the use of bioflocculants for sludge settling and dewatering. To achieve bioflocculation, extracellular polymeric substances (EPS) producing bacterial strains were isolated from the complex microbial community of wastewater sludge. Crude EPS produced in the form of bacterial broth was used to test kaolin flocculation activity. Three out of 10 bacterial strains (B2, B8 and B9) were pre-selected for sludge settling. Based on sludge settling and dewatering results, B8 possessed better flocculating property than other bacterial strains. These sludge microorganisms were identified based on their 16S rDNA sequences and bacterial strain B8 was identified as Serratia sps.
Subject(s)
Bacteria/isolation & purification , Extracellular Space/chemistry , Polymers/isolation & purification , Sewage/microbiology , Waste Disposal, Fluid/methods , Water Microbiology , Water/chemistry , Bacteria/genetics , Bacteria/metabolism , Extracellular Space/metabolism , Flocculation , Genes, rRNA , Polymers/chemistry , Polymers/metabolism , Sequence Analysis, DNA , Sewage/analysis , Sewage/chemistry , Water/analysisABSTRACT
Polyhydroxyalkanoates (PHAs) accumulating bacteria were isolated from activated sludge samples collected from municipal wastewater treatment plants in Quebec. Twelve bacterial strains were screened for PHA production with acetate as sole carbon source. PHA granules exhibited a strong orange fluorescence when stained with Nile blue A observed under microscope (X100x). PHA was also analyzed by Gas Chromatography Linked to Mass Spectroscopy (GCMS) to further confirm the presence and the concentration of PHA. To compare the abilities of these PHA accumulating bacterial strains, synthetic media with acetate as carbon source was prepared to accumulate PHA in 500 mL Erlenmeyer flask containing 150 of the medium. These flasks were then inoculated with the isolated bacterial strains, incubated at 25 degrees C for 48 hours in a rotary shaker at 220 rpm. The results showed that the bacterial strains isolated from sludge possess different abilities for accumulating PHA. The maximum PHA content of 27.50% was obtained by strain PHA-SB3. The PHB/PHV ratio of the copolymer produced in the study changed in accordance with operating time and strains.
