**Answer:**

volume of biological sludge = 28.566 m³ per day

**Explanation:**

given data

mass of solid = 7240 kg/day

initial moisture content = 78%

solution

here percentage of solid will be

% of solid = 100 - initial moisture content

% of solid = 100 - 78 = 22 %

so that

mass of sludge produced = kg per day

put her value

mass of sludge produced = kg

mass of sludge produced = 32909.09 kg

so

specific gravity of sludge =

and as we know that

= 1.152

so that

density of sludge = S sludge × density of water

density of sludge = 1.152 × 1000

density of sludge = 1152 kg/m³

so that

volume of biological sludge =

volume of biological sludge =

volume of biological sludge = 28.566 m³ per day