CE 342 Wastewater Treatment L1-3

Typical parameter of influent solids in municipal wastewater plants

220 mg/L SS

what is the typical BOD measurement in a municipal wastewater treatment plant?

220 mg/L

what is the typical nitrogen measurement in a municipal wastewater treatment plant?

40 mg/L

what is the typical phosphate measurement in a municipal wastewater treatment plant?

8 mg/L

define oxygen demand

the amount of oxygen consumed in response to a particular contaminant

what is BOD?

measures how much oxygen gets consumed by microbes

what is L_t ?

the amount of biochemical oxygen demand that is left at time t

what do municipal wwtp need to monitor?

solids, BOD, nitrogen, and phosphate

general steps for TOC

1) oxidation reaction to find moles of carbon

2) find molecular weights

3) calculate mg/L of carbon

ideal batch reactor

no flow; perfect mixing

ideal pfr

continuous flow; no axial mixing

ideal cstr characteristics

continuous flow; perfect mixing

what is this equation:

t_d = HRT = θ_h = reactor volume/ effluent flow rate

theoretical detention time

true or false: hydraulic residence time equals theoretical detention time

true

QC_in

mass application rate or process loading rate

what is the general formula for a mass balance?

accumulation = input - output ± source/sink ± reaction

explain what a pulse input tracer test does

puts a slug of tracer into the influent at one time to observe how the water flows through a reactor

what is a step input tracer test?

at time zero, a concentration of tracer is continuously added into a reactor influent for the theoretical detention time being observed

R =kC⁰ = k

zero order

R = kC¹

first order

R = kC²

second order

when are reaction rates positive?

pollution formation or bacterial growth

when are reaction rates negative?

contamiation degreadation or removal

purpose of preliminary treatment

remove material that could create damage in downstream components of treatment

do prelim WWTP processes decrease BOD much?

no. they’re not targeting BOD and instead focus on solids removal

what is the importance of the head loss equation through bar screens

to determine the energy and hydraulic drop across the screen, ensuring the wastewater collection and treatment system functions without overflowing or failing

what is the importance of the grit chamber settling tank?

removes heavy, dense inorganic solids before the water reaches sensitive downstream equipment.

equalization: pre treatment cstr used to

smooth out any time varying flow and concentration

flow equalization

dampens the flow fluctuations in variable volume cstrs; typically added after the bar rack/grit chamber

in an equalization tank, what happens when Q_in > Q_avg

the volume in the equalization tank increases

in an equalization tank, what happens when Q_in < Q_avg

the volume in the equalization tank decreases