# GATE Questions & Answers of Quantity and characteristics of wastewater

## What is the Weightage of Quantity and characteristics of wastewater in GATE Exam?

Total 7 Questions have been asked from Quantity and characteristics of wastewater topic of Water and Waste Water subject in previous GATE papers. Average marks 1.71.

The ultimate BOD (L0) 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 $\style{font-family:'Times New Roman'}{\mathrm\theta}$ = 1.047, the BOD value (in mg/L, up to one decimal place) after three days of incubation at 27oC for this wastewater will be ______

The wastewater from a city, containing a high concentration of biodegrable organics is being steadily discharged into a flowing river at a location S. If the rate of aeration of the river water is lower than the rate of degradation of the organics, then the dissolved oxygen of the river water

Two wastewater streams A and B having an identical ultimate BOD are getting mixed to form the stream C. The temprature of the stream A is 20ºC and the temprature of the stream C is 10ºC. It is given that

$\bullet$ the 5-day BOD of the stream A measured at 20ºC = 50mg/l

$\bullet$  BOD rate constant (base 10) at 20ºC =0.115 perday

$\bullet$ temperature coefficiant = 1.135

The 5-day BOD (in mg/l,up to one decimal place) of the stream C, calculated at 10ºC, is __________

For a given water sample, the ratio between  $\style{font-family:'Times New Roman'}{{\mathrm{BOD}}_{5-\mathrm{day}.20^\circ\mathrm c}}$ and the ultimate $BOD$ is 0.68. The value of the reaction rate constant $k$(on base $e$) (in day-1,up to two decimal places) is __________

Effluent from an industry 'A' has a pH of 4.2. The effluent from another industry 'B' has double the hydroxyl (OH-) ion concentration than the effluent from industry 'A'. pH of effluent from the industry 'B' will be __________