GATE CE 2018 Paper 1 — page 21

Questions 61–63 of 65. Imported answers require review unless explicitly marked reviewed.

A water sample analysis data is given below.

Ion	Concentration, mg/L	Atomic Weight
Ca²⁺	60	40
Mg²⁺	30	24.31
HCO₃⁻	400	61

The carbonate hardness (expressed as mg/L of CaCO₃, up to one decimal place) for the water sample is _____

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The ultimate BOD (

) of a wastewater sample is estimated as 87% of COD. The COD of this wastewater is 300 mg/L. Considering first order BOD reaction rate constant k (use natural log) = 0.23 per day and temperature coefficient

= 1.047, the BOD value (in mg/L, up to one decimal place) after three days of incubation at 27°C for this wastewater will be _____

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A waste activated sludge (WAS) is to be blend with green waste (GW). The carbon (C) and nitrogen (N) contents, per kg of WAS and GW, on dry basis are given in the table.

Parameter	WAS	GW
Carbon (g)	54	360
Nitrogen (g)	10	6

The ratio of WAS to GW required (up to two decimal places) to achieve a blend C:N ratio of 20:1 on dry basis _____

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2018 · Paper 1

Question 51

Question 52

Question 53