Global expansion in energy demand has convinced energetic search for alternative energy
sources. Biogas is an energy-rich combination of mainly methane and carbon dioxide and can be
used for active purposes. It is a cheap way to meet energy crises. It is an odorless, colorless and
flammable gas with an energy content of 37.3 MJ/m3. It is produced by process of anaerobic
digestion comprising of three steps i.e. hydrolysis, acidogenesis/acetogenesis and
methanogenesis. Out of the 14 drains in Lahore, sludge samples were collected from Samanabad,
outfall and Gulshan-e-Ravi drains. These samples were analyzed for Electrical conductivity (HI
8633 EC meter), pH (HI 2210 pH meter), BOD5 (HI 9146 DO meter), Total carbon content,
Nitrogen (Kjeldhal’s method), Phosphorus (V-110 spectrophotometer), Potassium (Multichannel
Flame photometer-AFP 100) and Heavy metals (including Cr, Cu, Pb, Zn and Ni by
Polarized Zeeman Z-8230 Atomic Absorption Spectrophotometer).
pH went from 6.37 to 7.66 (from slightly acidic to basic in nature) inside the biogas digesters
while temperature inside the biogas digesters ranged from 26.1°C-32.2°C. Electrical conductivity
of sludge samples varied from 1.38 mS/cm to 2.23 mS/cm and TDS ranged from 883.2 mg/l to
1427.2 mg/l. Carbon content of wastewater sludge ranged from 1.3983 g to 2.3677 g while total
Kjeldhal’s nitrogen varied from 40.6 mg/l to 59.2 mg/l. Nutrients like Phosphorus varied from
15750 ppm to 17250 ppm and Potassium ranged from 602.5 ppm to 9775.5 ppm in sludge
samples. Concentration of heavy metals i.e. Lead (Pb) in sludge samples varied from 2.58 ppm
to 2.94 ppm, Copper (Cu) went from 0.05 ppm to 0.79 ppm, Zinc went from 5.13 ppm to 5.28
ppm, Nickel (Ni) ranged from 0.11 ppm to 0.35 ppm while Chromium (Cr) was not detected in
samples.
Summary
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Variation in water concentration in the digesters of drain A made a difference of 900.800 ppm in
CH4 concentration, 0.016 % vol of CO2, 0.020 in pH and 1.090 °C in temperature. While
variation in water concentration in the digesters of drain B made a difference of 483.499 ppm in
CH4 concentration, 0.331 % vol of CO2, 0.019 in pH and 0.110 °C in temperature. And in that of
the digesters of drain C made a difference of 238.295 ppm in CH4 concentration, 0.187 % vol of
CO2, 0.015 in pH and 0.490 °C in temperature. Highest methane potential was found in Drain A,
followed by drain B and C. Absence of H2S shows that the biogas produced anaerobically from
the municipal wastewater sludge can be an environmentally friendly source of energy.