Wastewater Treatment Essays - Sewerage, Environmental Engineering

Wastewater Treatment The reason for me doing this report is because I could not attend class enough to grasp the concept of Wastewater Treatment. This report is an overview of each stage of the treatment of sewage. I have included a diagram of a typical sewage plant. A) Primary Treatment The wastewater that enters a treatment plant contains debris that might clog or damage the pumps and machinery. The material is removed by screens, and is burned or buried. The wastewater then passes through a comminutor (grinder), where all the organic material such as leaves are mushed smaller so that they can be removed later. 1) Grit Chamber Back in the day, long narrow channel-shaped settling tanks, known as grit chambers, were used to remove all the inorganic substances like sand, silt, gravel, and cinders. These chambers were made to allow inorganic particles 0.008 in. or bigger to settle at the bottom while the smaller particles and most of the organic material that remain in suspension pass through. Today, spiral-flow aerated grit chambers with hopper bottoms, or clarifiers with automatic scrapper arms are used. The grit is removed and disposed of as sanitary landfill. Grit build up can reach from 3 to 8 cubic feet per1 million gallons of wastewater. 2) Sedimentation With the grit removed, the wastewater goes into a sedimentation tank, where the organic materials removed. The method of sedimentation can remove about 20 to 40 percent of the biochemical oxygen demand and 40 to 60 percent of the suspended solids. The big boys in the industry use a chemical process known as coagulation and flocculation in the sedimentation tank. I really don't know much about this subject so I'm going to move on. 3) Flotation The alternative to sedimentation is a treatment called flotation, in which air is forced into the wastewater under pressures of 25 to 50 lbs per sq. in. The wastewater, is compressed with air, is then released into an open tank ; there the rising air bubbles cause the suspended solids to rise to the surface, where the are wisked away. Flotation can remove more than 75 percent of the suspended solids. 4) Digestion Digestion is a microbiological process that changes the chemically complex sludge to methane, carbon dioxide, and a harmless fertilizer. The reactions occur in a closed tank or digestor that is oxygen deficient. The transformation happens after a series of reactions. First the solid matter is made soluble by enzymes, then the substance is fermented by a group of acid-producing bacteria, reducing it to simple organic acids such as acetic acid. The organic acids are then resolved to methane and carbon dioxide by bacteria. The sludge that is to thick is heated and added to the digester as many times as possible, where it sits for 10 to 30 days and is decomposed. Digestion reduces organic matter by 45 to 60 percent. 5) Drying The digested sludge is place on sand beds for air drying. Air drying needs dry, warm weather for it to work. Some plants have shelters over the sand beds. Dried sludge in most cases is used as a fertilizer because of the 2 percent nitrogen and 1 percent phosphorus content. B) Secondary Treatment After removing 40 to 60 percent of the suspended solids and 20 to 40 percent of the BOD5 in the primary stage by physical resources, the secondary treatment biologically reduces the organic material that stayed in the liquid stream. Secondary treatment contains keeping and speeding up nature's process of waste disposal. Aerobic bacteria in the oxygen change the organic matter to stable forms such as CO2 , water, nitrates, and phosphates. The new organic material that is made is an indirect result of biological treatment processes, and is removed before the wastewater is dumped into the streams. 1) Trickling Filter In this process, a waste stream is sent over a bed or column of some type of porous medium. A sticky film of microorganisms coats the medium and acts as the removal agent. The organic matter in the waste stream is absorbed by the film and changed to carbon dioxide and water. If the trickling filter step comes before the sedimentation stage it can remove about 85 percent of the BOD entering the plant. 2) Activated Sludge This stage is an aerobic process that adds sticky sludge particles that have millions of of actively growing bacteria stuck together by a gelatinous slime. Organic matter is assimilated by the floc and changed to aerobic output. The reduction of BOD varies between 60 to

What Can You Find From A Sample Of Personal Reflection Essay?

What Can You Find From A Sample Of Personal Reflection Essay?There are many different forms of essay writing that you can find when it comes to personal reflection. Many writers feel that the best way to write an essay is by using a sample of personal reflection essay. While many writers prefer to write essays for different reasons, the most common reason people go to write an essay is to use it as a tool to better themselves and learn more about who they are.The sample of personal reflection essay can be found in many different places. The first place to look for a sample is in your school's library. If you take a look around the school library, you will most likely see a large collection of essays that have been created over the years from different students, professors, and even the Library Association.The teachers and professors of the school often choose different topics for different groups. This can also help to find out what kinds of subjects are very popular and what types o f topics are the most difficult. You may be surprised at how many times you find a sample of a personal reflection essay in these books.You may also find some samples online if you do a quick search in online sources. Many websites give you samples of personal reflection essays that are available for the use of anyone. While you might find some sites that offer free samples, the more popular websites usually allow you to pay a fee to access the materials you want to download.While there are many different personal reflection essay samples available online, there are many things that you need to keep in mind when choosing a sample. The most important thing that you need to look for is the content. It should be able to be easily understood by anyone and should be something that will be useful to the student.The other thing you need to look for is the material's format. Often times, a writer will not only use a sample of personal reflection essay for personal reflection purposes, but t hey also will use it for their class work as well. If you choose a website that offers many different options, you may find it is much easier to find a sample of a personal reflection essay that you will be comfortable with.Once you have decided on the type of essay that you want to use, you will want to use a website that gives you the opportunity to download your essay. Most sites will give you the ability to download the essay straight to your computer for personal use. While there are many sites that allow you to download for free, you will want to take a look at the site's policies before you do so.Finding a sample of personal reflection essay will not only help you to gain experience when it comes to writing, but it will also help you to prepare yourself when you finally choose to write one. It is a good idea to go back to different samples and see what kind of style the person who wrote the essay uses when writing it. You will then be able to determine if the style is somethi ng that you can do well and if you are comfortable writing in this style.