1-6. In a biological waste treatment system, solids may enter in the influent, be created or destroyed by biological growth or decay, and may leave in the effluent. Con- sider a waste treatment plant treating 1m/s of an influent containing 55 mg/L of degradable organic solids. The wastewater also contains 180 mg/L of dis- solved organic carbon (DOC), which may be degraded. For every gram of dissolved organic matter that is degraded, the overall reaction converts a portion of the material into CO, and H2O, and another portion into 0.4g of new biomass. Analytically, this biomass and the degradable solids in the influent are both quantified as volatile suspended solids (VSS); that is, the degradable solids in the influent and the new biomass that grows in the reactor are indistinguishable from one another. (a) In a particular system, the dissolved organic matter (i.e., the substrate, S) is removed from solution at an overall rate (including both the conversion into CO, and into new cells) given by rs = -k,SX/(S² + K,), where X is the VsS con- centration in the reactor. The values of k, K,, and X in the reactor of interest are 8 mg DOC/mg VSS d, 110 (mg DOC/L)², and 120 mg VSS/L, respec- tively. Write a mass balance and compute the hydraulic detention time, t (i.e., the average amount of time that water resides in the reactor, equal to V/QL) necessary to reduce the concen- tration of substrate to 3 mg DOC/L in a complete mix reactor operating at steady state. (b) Solids decay in the reactor at a rate equal to kaX, where ka is the decay rate constant. Write a mass balance on VSS and compute the value of k4.
1-6. In a biological waste treatment system, solids may enter in the influent, be created or destroyed by biological growth or decay, and may leave in the effluent. Con- sider a waste treatment plant treating 1m/s of an influent containing 55 mg/L of degradable organic solids. The wastewater also contains 180 mg/L of dis- solved organic carbon (DOC), which may be degraded. For every gram of dissolved organic matter that is degraded, the overall reaction converts a portion of the material into CO, and H2O, and another portion into 0.4g of new biomass. Analytically, this biomass and the degradable solids in the influent are both quantified as volatile suspended solids (VSS); that is, the degradable solids in the influent and the new biomass that grows in the reactor are indistinguishable from one another. (a) In a particular system, the dissolved organic matter (i.e., the substrate, S) is removed from solution at an overall rate (including both the conversion into CO, and into new cells) given by rs = -k,SX/(S² + K,), where X is the VsS con- centration in the reactor. The values of k, K,, and X in the reactor of interest are 8 mg DOC/mg VSS d, 110 (mg DOC/L)², and 120 mg VSS/L, respec- tively. Write a mass balance and compute the hydraulic detention time, t (i.e., the average amount of time that water resides in the reactor, equal to V/QL) necessary to reduce the concen- tration of substrate to 3 mg DOC/L in a complete mix reactor operating at steady state. (b) Solids decay in the reactor at a rate equal to kaX, where ka is the decay rate constant. Write a mass balance on VSS and compute the value of k4.
Chapter2: Loads On Structures
Section: Chapter Questions
Problem 1P
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can you put the values in the mass balance?
what is the answer of part b of this question?
Transcribed Image Text:1-6. In a biological waste treatment system, solids may enter
in the influent, be created or destroyed by biological
growth or decay, and may leave in the effluent. Con-
sider a waste treatment plant treating 1m'/s of an
influent containing 55 mg/L of degradable organic
solids. The wastewater also contains 180 mg/L of dis-
solved organic carbon (DOC), which may be degraded.
For every gram of dissolved organic matter that is
degraded, the overall reaction converts a portion of
the material into CO, and H20, and another portion into
0.4 g of new biomass. Analytically, this biomass and the
degradable solids in the influent are both quantified as
volatile suspended solids (VSS); that is, the degradable
solids in the influent and the new biomass that grows in
the reactor are indistinguishable from one another.
(a) In a particular system, the dissolved organic matter
(i.e., the substrate, S) is removed from solution at
an overall rate (including both the conversion
into CO, and into new cells) given by
rs = -k,s°X/(S² + K,), where X is the VsS con-
centration in the reactor. The values of k1, K, and X
in the reactor of interest are 8 mg DOC/mg VSS d,
110 (mg DOC/L)², and 120 mg VSS/L, respec-
tively. Write a mass balance and compute the
hydraulic detention time, t (i.e., the average
amount of time that water resides in the reactor,
equal to V/QL) necessary to reduce the concen-
tration of substrate to 3 mg DOC/L in a complete
mix reactor operating at steady state.
(b) Solids decay in the reactor at a rate equal to kax,
where ka is the decay rate constant. Write a mass
balance on VSS and compute the value of ka.
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