Environmental Engineering - Wastewater Treatment

Which of the following components is/are NOT removed in the secondary treatment of sewage?

One-third of the solid matter in a sludge containing 90% water is composed of fixed mineral solids with specific gravity 2.5, and two-third is composed of volatile solids with specific gravity 1.0. Specific gravity of al...

The grown algae are useful in the operation of

The average sewage from a city is 90 million litres per day and the average 5-day Biochemical Oxygen Demand (BOD5) is 300 mg/l. Average standard BOD5 of the domestic sewage is 0.08 kg/day/person. The population equivalen...

An Activated Sludge Process (ASP) has an inlet wastewater flowrate of 20000 m³/day with a Biochemical Oxygen Demand (BOD) concentration of 250 mg/l. It produces treated wastewater containing 20 mg/l BOD. The aeration tan...

Anaerobic bacteria are being utilized for the destruction of biodegradable organic content of wastewater measured in terms of Chemical Oxygen Demand (COD). The yield coefficient (Y) is 0.06 gram Volatile Suspended Solids...

The bacteria mainly responsible for crown corrosion in a sewer is ________.

A facultative pond system is employed for wastewater treatment. Which of the following statements is/are true:

A community generates 1 million litres/day (MLD) of wastewater. This wastewater is treated using activated sludge process (ASP). The working volume of the aeration tank of the ASP is 250 m³, and the biomass concentration...

Which one of the following products is NOT obtained in anaerobic decomposition of glucose?

A circular settling tank is to be designed for primary treatment of sewage at a flow rate of 10 million liters/day. Assume a detention period of 2.0 hours and surface loading rate of 40000 liters/m²/day. The height (in m...

Activated carbon is used to remove a pollutant from wastewater in a mixed batch reactor, which follows first-order reaction kinetics. At a reaction rate of 0.38 /day, the time (in days) required to remove the pollutant b...

The wastewater inflow to an activated sludge plant is 0.5 m³/s, and the plant is to be operated with a food to microorganism ratio of 0.2 mg/mg-d. The concentration of influent biodegradable organic matter of the wastewa...

For wastewater coming from a wood pulping industry, Chemical Oxygen Demand (COD) and 5-day Biochemical Oxygen Demand (BOD5) were determined. For this wastewater, which of the following statement(s) is/are correct?

A wastewater sample contains two nitrogen species, namely ammonia and nitrate. Consider the atomic weight of N, H, and O as 14 g/mol, 1 g/mol, and 16 g/mol, respectively. In this wastewater, the concentration of ammonia...

A sewage treatment plant receives sewage at a flow rate of 5000 m³/day. The total suspended solids (TSS) concentration in the sewage at the inlet of primary clarifier is 200 mg/L. After the primary treatment, the TSS con...

A secondary clarifier handles a total flow of 9600 m³/d from the aeration tank of a conventional activated-sludge treatment system. The concentration of solids in the flow from the aeration tank is 3000 mg/L. The clarifi...

A grit chamber of rectangular cross-section is to be designed to remove particles with diameter of 0.25 mm and specific gravity of 2.70. The terminal settling velocity of the particles is estimated as 2.5 cm/s. The chamb...

Surface Overflow Rate (SOR) of a primary settling tank (discrete settling) is 20000 litre/m² per day. Kinematic viscosity of water in the tank is 1.01×10⁻² cm²/s. Specific gravity of the settling particles is 2.64. Accel...

A wastewater is to be disinfected with 35 mg/L of chlorine to obtain 99% kill of micro-organisms. The number of micro-organisms remaining alive (Nt) at time t, is modelled by Nt = No e^-kt, where No is number of micro-or...

A schematic flow diagram of a completely mixed biological reactor with provision for recycling of solids is shown in the figure. So, S = readily biodegradable soluble BOD, mg/L Q, Qr, Qw= flow rates, m³/d Xo, X, Xe, Xu =...

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 coeff...