Take Home Quiz

Technological Institute of the Philippines 1338 Arlegui St. Quiapo, Manila

College of Engineering and Architecture Department of Chemical Engineering

Saurin, Anthony DV. 0810096 CHEP523 –  CHEP523 – Industrial Industrial Waste Management and Control Dr. Florante Magnaye PhD. Take Home Quiz

What are some of the problems of the BOD test?

Since the BOD test is dependent on biological activity, the major interferences will be those substances which inhibit the growth of the microorganisms. microorganisms. These will include chlorine, caustic alkalinity or acidity, mineral acids, and heavy metals (such as copper, zinc, chromium, and lead).

Excessive nitrites can interfere with the BOD BOD determination. Growth of algae in the  presence of light can cause problems by actually actu ally increasing the DO of the sample before testing, which must be removed by deaeration.

A common problem encountered in BOD testing results from residues building up in the BOD and dilution water bottles. To prevent this, this, all glassware glassware should be acid cleaned on a regular basis.

Explain the difference between carbonaceous BOD and autotrophic BOD.

Carbonaceous biochemical oxygen demand (CBOD) is the result of the breakdown of  organic molecules such a cellulose and sugars into carbon dioxide and water on the other hand autotrophic biological oxygen demand is the exerted by autotrophic microorganisms such as nitrifiers.

You have been asked by a wastewater agency to review the adequacy of their odor-control program. What would be your major considerations in making such review? 

What causes the Odor?

There substances that are responsible for the diffusion of odors into the atmosphere these substances are generally gaseous inorganic products or highly volatile organic compounds. The following compounds are associated with bad odors: mercaptans, skatoles, indoles, inorganic acids, aldehydes, ketones and organic compounds containing nitrogen or sulfur atoms. These compounds can originate from the anaerobic decomposition of compounds with a high molecular  weight, especially proteins. These are recognized as being among the causes of bad-smelling odors at the outlet of sewer lines and in treatment plants in general. 

How bad is the odor?

There are some parameters to express the concentration of odors: Perceptibility

Threshold

(ATC:

Absolute

Threshold

Concentration)

is

the

minimum

concentration that can be detected by 100% (in some cases by 50%) of the persons involved with an olfactory analysis. Odor Number (TON: Threshold Odor Number), or the number of dilutions needed to reduce the concentration of the sample to the ATC. Maximum Exposure Concentration (TLV: Threshold Limit Value) is the representation of the maximum concentration at which persons can be exposed for a period of 8 hours a day, 5 days a week and 50 weeks a year (weighted average over 8 hours), for a work life of 40 years. Maximum Allowable Concentration (MAC: Maximum Allowable Concentration): Maximum concentration which should never be exceeded. 

How will it be treated?

Thermal Oxidation Thermal oxidation systems essential burn odor causing compound either directly or catalytically with or without heat recapture. Typically they are used to deal with volatile organic compounds with odor control being a secondary benefit. Thermal oxidation treatment, though efficacious in some applications and compact, involves high installation and operating costs (using fuels as “oxidizing” material) which are recommended only in specific cases. As a result they are used only for very high strength odors or very difficult to treat compounds.

Bio Filters Bio filters remove odor by capturing the odor causing compounds in a media bed where they are oxidized by naturally occurring micro organisms. These systems have a low profile and thus don’t obstruct views. They are also relatively simply to use and are effective if properly designed and maintain. Chemical Scrubbing and Oxidation Multi stage scrubbers can remove a wide range of odor causing compounds both acidic and  basic. They have been proven to be effective in many applications. Typically these systems are employed with high intensity odors in large air volumes. There are several types of wet scrubbers including packed bed, mist, and venturi scrubbers. All are designed to maximize the contact  between the odorous compounds of the foul air stream and a "scrubbing" chemical solution. The compounds are absorbed and then oxidized by the chemicals.

In wastewater treatment, nitrogen removal is one under tertiary treatment. Compare and contrast nitrogen removal using chemical and biological processes.

In nitrogen removal in the wastewater, chemical processes are more adaptable in the fluctuating flow and concentrations inherent in the most wastewater treatment and more amenable, example of this process are air stripping, ion exchange, chlorination, precipitation and activated carbon that eliminates organic nitrogen. By the way, biological nitrogen removal uses  bacteria in removing nitrogen which can only achieve in specific environmental condition.

Compare and contrast suspended growth and attached growth process.

Suspended growth process uses sedimentation in removing the biological solid in the wastewater  in contrast with attached growth process the solid media is added to the reactor to provide attachments surfaces for biofilms that could result in increasing of microbial concentrations and elevate the rates of contaminants degradation.