a. We put a lot of time and effort into cultivating our activated sludge microbi

Question

a. We put a lot of time and effort into cultivating our activated sludge microbial community. So why do we waste sludge out of it? b. A wastewater discharges to Puget sound, a marine water where nitrogen is the limiting nutrient for algal growth. Sketch what the wastewater plant activated sludge process probably looks like. c. A wastewater plant has been designed to handle an average daily flow of 5MGD with a commensurate BOD concentration of 400mg/L. The plant PEAK flows, however, are 13MGD: at that flow rate, the BOD is diluted to 250mg/L. Upstream of the one AS basin are two primary clarifiers that split the influent flow equally between them; the clarifiers typically remove 25% of the BOD load. i) What are the BOD loads to the plant at each influent flow rate? ii) And to the Activated sludge (AS) basin? iii) If the influent quality is to stay same at each of these loads, how will the plant adjust their wasting rate (do not need a number, just a description). iv) If the MLSS concentration (X) is 4500mg/L, what is the maximum specific growth rate we could expect at the average BOD concentration? v) The aeration basin is 1MG. Assuming Y is 0.6, b is 0.08 and the permit is written for a BOD effluent concentration of 15mg/L, what SRT should the plant maintain to keep X at 4,500mg/L under average daily conditions? vi) Under peak flow conditions? vii) What is the F:M ratio of each of the flow conditions if the MLSS concentration is 4,500mg/L? viii) During peak flow event, one of the primary clarifiers is hydraulically overwhelmed and can only remove about 10% of the influent BOD. The other clarifier functions as normal. The peak flows also washed some of the bacteria out of the system before the plant had time to adjust their wasting rate, so X has dropped to 3,500mg/L. What will be the BOD concentration out of the AS basin under these circumstances? Assume Y and b are the same as in (v) above, and that the peak flow SRT calculated in (vi) is still the target SRT. ix) The peak flow only last for four hours, but the grit chamber can barely keep up with a flowrate of 10MGD. The plant has made up for this deficit by providing equalization (EQ) storage to hold the excess flow until the influent flowrate drops. How big does the EQ basin have to be to prevent the grit chamber from overflowing? x) The flows are from snow that piled up during a blizzard. The weather is now warm enough to melt all the snowmen and wash them into the combined sewers that feed the plant. In preparation for and during the blizzard, the city put sand on all the roadways, which is also now washing into the combined sewers. xi) What influent parameter will the sand most affect? xii) Where will the sand largely end up?

Explanation / Answer

Activated sludge plays a crucial role in the treatment of domestic and industrial waste water.Activated sludge is a biogenesis of microorganisms capable of degrading various, pollutants, including organic compounds,toxicants , and xenobiotics. We performed 16S rRNA gene sequencing of activated sludge and incoming sewage in three wastewater treatment plants responsible for processing sewage with different origins.

Municipal waste water,slaughterhous wastewater and refinery sewage.In contrast to incoming waste water,the taxonomic structure of activated sludge biocenosis was found to become stable in time and each waste water treatment plants demonstrated a unique taxonomic pattern. Most pathogenic microorganisms (Streptococcus,Trichococcus,etc),which are abundantly represented in incoming sewage ,were significantly decreased in activated sludge decreased in activated sludge of all wastewater treatment plants , except for the slaughterhouse wastewater. Additional load of bioreactors with influent rich in petroleum products and organic matter was associated with the increase of bacteria responsible for activated sludge bulking and forming.

Domestic and industrial wastewater detoxification is of vital importance for the production of natural ecosystem and human health.wastewater processing is usually performed in several steps,including mechanical and biological treatment.

Activated sludge is composed of aerobic and anaerobic microorganisms such as bacteria,Archaean,fungi,and protists.it is capable of degrading organic compounds,includ inc petroleum products toluene,and benzopyrene.

The aquatic environment of a city is a system in which each subsystem Is influenced by the subsystem upstream of it and opens up the possibility for preparing sewage for treatment at wastewater treatment plants. in order to optimize the purification process and enhance the elimination of xenobiotics and pathogenic microorganisms at the treatment plants the sewer network should be considered as an intiali easwastewa treatment system.

It is possible to create a technical frame work for the formation of a given bacterial community which is in the sewer network by adding a special loading system to mixing chambers and creating anaerobic or aerobic reactors. this approach will significantly increase the time available for useful bacterial community to form in the wastewater. The removal of these waste components is the most energy and resources consuming step and there is still no reliable biological method to remove many xenobiotics pollutants.

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