Wastewater treatment – teaching materials for AGH UST students
Prepared by Anna Dworakowska (AGH UST)
WASTEWATER TREATMENT
INTRODUCTORY QUIZ
Discuss the following questions with your partner(s) :
1. Define the process of sewage treatment.
2. What different types of sewage can we distinguish?
3. What different general types of sewage treatment processes do you know?
4. What is produced in the sewage treatment process?
5. What is the difference between “grey water” and “black water”?
SEWAGE COLLECTION SYSTEMS
Please fill in the following text with the words from the box
Modern sewer systems typically are (1)_____________ pipelines installed below the ground surface in streets
and following the ground slope. The depth of cover over pipelines is controlled by factors such as the location
of rock and (2) _____________, the ability to receive flows from all buildings by gravity, depth of (3)
_____________, economics of maintaining gravity flow as compared with pumping, and location and elevation
of other existing (4) _____________ and infrastructures.
Maintaining gravity flow can require deep excavations in hilly or flat terrain, driving up (5) _____________.
Sewage (6) _____________ may be necessary due to slope requirements for conventional gravity sewers. This
results in a system terminus (i.e., low spot) at the (7) _____________ of the sewer, where sewage collects and
must be pumped or lifted to a collection system. Pumping and lift stations substantially increase the cost of the
collection system. (8) _____________ associated with conventional gravity sewers are a source of inflow and
infiltration, increasing the volume of wastewater to be carried, as well as the size of pipes and lift/pumping
stations, and, ultimately, increasing costs.
In Poland a lot of households, especially in the countryside, are still not connected to the sewage collection
network and have to use (9) _____________, which are later emptied by means of (10) _____________.
Sewage collection systems can be also divided into combined and separate sewers. Combined sewer systems
are designed to transport both (11) _____________ and sewage in the same pipe. Besides the projected
sewage flow, the size and characteristics of (12) _____________ are the overriding design considerations for
combined sewers. Often, combined sewers cannot handle the volume of runoff, resulting in (13)
_____________ and causing water pollution problems in nearby water bodies. Separate (14) _____________
sewer systems are designed to transport sewage alone. In communities served by such sewers, another (15)
_____________ is constructed to convey storm water runoff directly to surface waters. Most (16)
_____________ sewer systems constructed today are separate sewer systems.
Adapted from: http://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P10053D9.txt
a. utilities b. septic tanks c. ground water d. sanitary e. municipal f. overflows g. frost line
h. storm water runoffs i. pipe system j. pumping or lift stations k. manholes l. precipitation
m. septic tankers or haulers n. gravity flow o. construction costs p. tail
Wastewater treatment – teaching materials for AGH UST students
Prepared by Anna Dworakowska (AGH UST)
A VISIT TO A WASTEWATER TREATMENT PLANT
Here's a step-by-step guide describing what happens at each stage of the treatment
process and how pollutants are removed to help keep our waterways clean. Read
through the text and match the underlined words with their Polish equivalents in the
box. Next answer the questions below.
PRIMARY, MECHANICAL TREATMENT
Wastewater entering the treatment plant includes items like wood, rocks, and even dead animals. Unless they
are removed, they could cause problems later in the treatment process. This is most commonly done with an
automated mechanically raked bar screen. Most of these materials are sent to a landfill or are incinerated.
Next, the sewage channel broadens out into the grit chamber, reducing the velocity of the sewage and allowing
coarser particles such as gravel and sand, which are heavier than water, to settle at the bottom. In the primary
settlement tank the water is kept for about two hours. In this large rectangular or round settlement tank fine
suspended particles can settle as sludge at the bottom. This raw sludge is removed, thickened and transferred
to a digestion chamber. Light particles floating on the water's surface such as fat and mineral oil are skimmed
off and discharged into a separate tank. Primary treatment allows for the physical separation of solids and
grease from the wastewater, and removes between 30-40 percent of Biological Oxygen Demand (BOD) and 50
per cent of Total Suspended Solids (TSS).
SECONDARY, BIOLOGICAL TREATMENT
In the second or biological purification stage a natural process is used by passing the wastewater into an
aeration tank. In an activated sludge process oxygen is inserted into the wastewater to create favourable
conditions for microorganisms which feed on solved organic particles in the sewage and accumulate the
ingested matter. During this process pollutants such as heavy metals are also ingested. A large number of
microorganisms form colonies which become visible as sludge flocs. These sludge flocs settle at the bottom of
the subsequent secondary settling pond or clarifier and are either returned to the activated sludge process or
pumped into the primary settling pond for sludge disposal. Smaller sewage treatment plants often use trickling
filters, i.e. round concrete tanks loosely filled with porous rocks which provide a large surface area needed by
the bacteria to settle. They form a continuous film over which the sewage is passed. Secondary treatment
removes up to 90 percent of BOD and TSS.
ADDITIONAL PURIFICATION
Today wastewater is generally polluted with chemical substances such as nitrogen and phosphate which makes
it necessary to apply additional special processes.
For example, effluent containing phosphate from the secondary settling pond goes into a flocculation chamber.
At this stage the effluent undergoes vigorous mixing and a dosing pump applies a chemical solution in the
liquor, which reacts chemically with the phosphates and forms a water-insoluble compound. Other
contaminants form flocs which settle in a clarifier as sludge. This sludge is thickened and transferred to the
digestion tank. The cleaned wastewater can now be discharged into the natural environment.
Adapted from: http://www.bmu.de/english/water_management/water_policy/wastewater/doc/3463.php
1.krata 2.żwir 3.komora fermentacyjna 4.piaskownik 5.przyswajana substancja 6.komora
napowietrzająca 7.biologiczne zapotrzebowanie na tlen 8.osad 9.zawiesina ogólna 10.zagęszczony
11.azot 12.utylizowany w spalarni 13.prędkość 14.fosforan 15.komora flokulacji 16.osadnik
17.drobne zanieczyszczenia, cząsteczki 18.klarownik, odstojnik 19.utylizacja odpadów 20.związek
nierozpuszczlny w wodzie 21.kłaczki osadu 22.betonowe zbiorniki 23.złoża biologiczne 24.osad czynny
Wastewater treatment – teaching materials for AGH UST students
Prepared by Anna Dworakowska (AGH UST)
In groups of three or more try to draw a diagram for each stage of sewage treatment:
mechanical, biological and additional. Be prepared to present it to the class .
INNOVATIONS IN WASTEWATER TREATMENT PROCESSES
What innovative solutions in wastewater treatment do you know?
You are going to see a short film about the NEWater project in Singapore. Answer the
questions.
1. What are the four main sources of water in Singapore (called national taps)?
2. What is NEWater?
3. What are the main three technologies applied in the production of NEWater?
4. Describe the membrane filtration process.
5. What does backwash mean? How long does it take? How often is it performed?
6. What are the advantages of Siemens microfiltration system?
7. Where is NEWater used?
8. Would you like to try NEWater?
9. What do you think about this solution? Do you think it could be applied in Poland?
VOCABULARY REVISION
Unscramble these words, all of them are connected with sewage treatment . Explain their
connection with this process
1.wgeaes 2.edlusg 3.soclf 4.reniotaa 5.netletstem 6.ynsiarat 7.nimupalci 8.ewrse
FOLLOW UP: SEWAGE TREATMENT IN KRAKOW
Collect information about the sewage treatment plant in Krakow (Płaszów) and the sewage treatment systems
applied there. Prepare a short presentation in English.
Questions to the text:
1. What is the purpose of mechanical treatment?
2. What processes/solutions are applied during primary
treatment?
3. What is the purpose of biological treatment?
4. What processes/solutions are applied during secondary
treatment?
5. Why additional purification (other than primary and
secondary) is necessary?
6. How phosphates are removed from sewage?