Waste Water Management

Jan 11 • General, Notes • 2128 Views • 12 Comments on Waste Water Management

Q1. What is meant by waste water?
Ans. Waste water is any water that has been adversely affected in quality by human impact on the environment.Waste water is liquid waste discharged by domestic residences, commercial properties, industry, agriculture, which often contains some contaminants that result from the mixing of waste water from different sources.

Q2. What do you mean by waste water management?
Ans. Any physical, chemical and biological processes used to modify the quality of waste water in order to make it more compatible or acceptable to humans is known as waste water management. Basically, waste water management or treatment is taking the sewage and holding it for a time to be treated.

Q3. How does Waste water management works?
Ans. Waste water treatment can encompass a number of steps, which filter, clarify and clean waste water from start to finish. Currently, the CRD region employs a variety of waste water treatments, some of which filter and some of which provide secondary treatment.

The steps involved are:
1. Preliminary treatment: Preliminary treatment takes out coarse solids, sand and gravel which are normally sent to landfill.

2. Primary treatment: Primary treatment screens waste water, and performs some rudimentary treatment to remove crude solids and skim off grease, oil and fat. Waste water sits in settling tanks, which are designed to hold the waste water for several hours. During that time, most of the heavy solids fall to the bottom of the tank, where they become a thick slurry known as primary sludge. The material that floats is also skimmed from the surface of the tanks. Both the primary sludge and skimmed material are typically pumped to a solids treatment processing plant.

3. Secondary treatment: Secondary (or biological) treatment removes dissolved oxygen-demanding organic substances by using bacteria to convert degradable organic matter into bacterial cells. These grown bacterial cells are then used to clearify the waste water.

4. Tertiary treatment: Tertiary treatment further treats effluent to remove nitrogen, phosphorus, fine suspended particles and microbes, and to kill or disable disease-causing organisms and viruses.

Q4. How do we measure flow?
Ans. Consider a container, like a five gallon bucket and put that five gallon bucket under the source and let it fill. The five gallon bucket fills in ten seconds. Now we have to find out number of gallons per minute. If the five gallon bucket does it in ten seconds, but we want to know how much it does in 60 seconds, so we take 5 x 60 ie. 30 gallons per minute. This was done by using ratio and proportion method. One minute is equal to 60 seconds. Multiply both sides by 60 seconds.

60 sec. ( 5 gal. ) ÷ ( 10 sec. ) = ( X gal/min ) ÷ 60 sec. ( 60 sec. )

Simplifying both sides equations, we get:

6 ( 5 gallons ) = X gal/min.

30 gallons = 1 minute

* So, the flow in gallons per minute (gpm) is 30 gallons per minute.

Q5. What do ou mean by retension or detension time?
Ans. Everything in water treatment depends upon the detention or retention time . To get that retention/detention time, we have to optimize the growth of whatever we are using or chemicals by controlling all those variables. This actually controls how fast we work. Everything takes time in retention/detention time.

Let’s do a retention/detention time problem.

If a containers size is 100,000 cubic feet and the flow is 200 gpm, will we get the proper treatment by the time we get to the other end. How much time are we going to have to treat it? How fast do our toxins work?

Remember : 1 cubic foot = 7.48 gallons

100,000 cubic feet = 748,000 gallons

So in order to find the time it’s going to take, divide 748,000 gallons by 200 gallons per minute.

748,000 gallons ÷ 200 gallons = 3,740 minutes

Then, to find the time in hours, divide the minutes by 60 minutes/hr.

3,740 minutes ÷ 60 min/hr. = 62 hours and 20 minutes

*This is the retention/detention time , or the amount of time the operator will have to treat the water.

Q6. Why chlorine is added to water?
Ans. Chlorine is a highly efficient disinfectant, and it is added to public water to kill disease-causing bacteria that the water or its transport pipes might contain.

Chlorine has been hailed as the savior against cholera and various other water-borne diseases. Its disinfectant qualities have allowed communities and whole cities to grow and prosper by providing disease-free tap water to homes and industry.

Q7. What is meant by “spray and pray”?
Ans. When we have an big oil spill like the Valdez , we spray microorganisms onto the site, onto the beaches and any effected area. We also spray fertilizers to help maintain these microorganisms to grow and eat this up. It’s “spray and pray”. Whether the conditions are right or not, we don’t know. Sometimes it works, sometimes it doesn’t. We really can’t predict what will happen, with all the things a microorganism needs. When we grow it in a lab, it’s got a specific pH, electrolytes and everything. It’s a controlled environment. When we spray it out there in nature, it’s an uncontrolled environment. We don’t know what will happen next.

Q8. What is package units?
Ans. The term “package units” is used in the field to describe equipment which has been put on the market by a number of manufacturers that is intended to provide wastewater treatment by the use of prefabricated or modular units. Package units can also refer to a complete installation, including both mechanisms and prefabricated containers. This term is also applied to installations where only the mechanisms are purchased and the containers constructed by the purchaser in accordance with plans and specifications prepared by the manufacturer.

Q9. What will be the consequence if waste water is not properly treated?
Ans. If wastewater is not properly treated, then the environment and human health can be negatively impacted. These impacts can include harm to fish and wildlife populations, oxygen depletion, beach closures and other restrictions on recreational water use, restrictions on fish and shellfish harvesting and contamination of drinking water.

Q10. Is ground water always clean?
Ans. No, ground water is not always clean. Groundwater can contain hydrogen sulfide (makes the water smell like rotten eggs) or other naturally occurring chemicals. Groundwater also may contain petroleum, organic compounds, or other chemicals introduced by human activities.Contaminated groundwater can occur if the well is located near land that is used for farming where certain kinds of chemicals are applied to crops or near a gas station that has a leaking storage tank. Leakage from septic tanks and/or waste-disposal sites also can contaminate groundwater.

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