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Table 1 Physicochemical and microbiological parameters of oily sludge samples

From: Petroleum hydrocarbon rich oil refinery sludge of North-East India harbours anaerobic, fermentative, sulfate-reducing, syntrophic and methanogenic microbial populations

  GR1 GR3 DB2
Parameters
 Site Guwahati Refinery, IOCL Guwahati Refinery, IOCL Digboi Refinery, IOCL
 Geographical location N 26° 10.48′ E 091° 48.00’ N 26° 10.48′ E 091° 48.00’ N 27° 23.410′ E 095° 36.665’
 Nature of the sample Oily sludge at waste disposal pit Oily sludge at waste water lagoon Oily sludge waste disposal pit
Physicochemical parameters
 Temperature (°C)a 35.2 44.9 35.6
 pH a 7.14 6.25 6.84
 Dissolved Oxygen (mg/l) a 0.66 0.19 0.01
 ORP (mV) a − 157.7 −30 − 182
 Conductivity (μS /cm) a 0.3 1.4 0
 Moisture content (%, w/w) 27.12 27.87 42.24
 TPH (g/ kg) 143.8 400 140.2
Hydrocarbons detected (%)b
 Total Aliphatic Compounds 60 71 75
 Total Aromatics 40 29 25
Ions (mg/kg)c
 Nitrate 18.24 7.87 13.63
 Nitrite 2.97 <  2.0 9.07
 Chloride 704.00 469.85 469.85
 Sulfate 6109 222 6621
 Phosphate 537.6 17 167
 Ammonium 3.24 3.49 3920
Metals (mg/kg)d
 Sodium 3.13 2.23 3.56
 Calcium 49.51 30.50 78.25
 Chromium 45.39 8.07 48.38
 Iron 150.47 302.97 101.13
 Cobalt 1.34 2.39 2.53
 Nickel 34.93 7.11 38.72
 Copper 12.92 2.39 12.89
 Zinc 34.70 131 68.14
 Arsenic 2.24 1.27 2.22
 Cadmium 0.06 0.16 0.05
 Lead 2.68 4.02 2.62
Microbial Counts
 Total microbial counts using fluorescence microscopy
(cells/g of sample)
(7.01 ± 0.87) × 108 ND (3.73 ± 0.68) × 108
CFU/g of samples
 MSM (1.65 ± 0.78) × 106 0.2 × 106 (5 ± 0.14) × 106
 R2A (8 ± 1.41) × 105 (6.5 ± 1.5) × 106 (7.35 ± 0.21) × 106
 Anaerobic agar (3 ± 0.14) × 105 (2 ± 0.7) × 106 (1.23 ± 0.14) × 106
Gene of interest Copy no./g sample   
Bacteria (16S rRNA gene) 4.46 × 109 2.35 × 1010 3.13 × 109
Archaea (16S rRNA gene) 2.54 × 108 1.01 × 108 1.04 × 108
mcrA 1.75 × 106 2.29 × 106 1.66 × 106
dsrB 2.22 × 108 4.02 × 107 3.48 × 108
  1. aMeasured during sample collection using Orion star series multiparameter (Thermo Orion meter Beverly, USA)
  2. bAnalysed and Identified by gas chromatograph coupled with mass spectrometer (GC-MS) (Perkin Elmer, USA)
  3. cEstimated by spectrophotometric and titrimetric methods of American Public Health Association
  4. dEstimated by ICP-MS (inductively coupled mass spectrometery) (Varian Palo Alto CA USA) and /or atomic absorption spectroscopy (AAS) (Perkin Elmer MA, USA)
  5. ND, Not detected