Table 1.
Physicochemical and microbiological parameters of oily sludge samples
| 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 |
aMeasured during sample collection using Orion star series multiparameter (Thermo Orion meter Beverly, USA)
bAnalysed and Identified by gas chromatograph coupled with mass spectrometer (GC-MS) (Perkin Elmer, USA)
cEstimated by spectrophotometric and titrimetric methods of American Public Health Association
dEstimated by ICP-MS (inductively coupled mass spectrometery) (Varian Palo Alto CA USA) and /or atomic absorption spectroscopy (AAS) (Perkin Elmer MA, USA)
ND, Not detected