This lecture note describes the process of Effluent Treatment (ET). Emphasis is give to the biological aspects of ET. Free to reuse, remix, modify and share for non-commercial and commercial purposes.

1. IB6033
Creative Commons License
EFFLUENT TREATMENT by KENNETH RODRIGUES is
licensed under a Creative Commons Attribution 4.0
International License.

2. INTRODUCTION
 The treatment of industrial effluents prior to release to the environment in a
complex process.
 Effluent treatment involves biological, chemical and physical processes.
 Within Malaysia effluents designated for release have to comply with federal
regulations.
 Environmental quality (sewage) regulations 2009 (PU (A)432)

3. EFFLUENT TREATMENT PLANT
https://youtu.be/FvPakzqM3h8

4. OBJECTIVES
 To introduce the concept of effluent treatment (ET).
 To introduce the key parameters associated with ET.
 To discuss the biological and chemical processes which are integral to ET.
 To apply knowledge of microbiology to understand effluent quality.
 To discuss effluent treatment within the context of Malaysian Regulations.

5. COURSE LEARNING OUTCOMES
Upon completion of this module, the participants should demonstrate the ability
to:
 Describe the process of ET.
 Define the key terms associated with ET.
 Propose specific solutions to address variation in the influent.
 Discuss ET within the context of Malaysian regulations.

6. KEY PARAMETERS
 Temperature
 Chemical Oxygen Demand (COD).
 Biochemical Oxygen Demand (BOD).
 Suspended Solids (SS)
 Oil and Grease.
 Nitrogen: Ammonical / Nitrite / Nitrite
 Phosphorus
 pH

7. COD
Chemical oxygen demand (COD) is an indicative measure of the
amount of oxygen that can be consumed by reactions in a measured
solution. It is commonly expressed in mass of oxygen consumed over
volume of solution which in milligrams per litre (mg/L).

8. BOD
Biochemical Oxygen Demand is the amount of dissolved oxygen
needed by aerobic biological organisms to break down organic
material present in a given water sample at certain temperature over
a specific time period.

9. NITROGEN
 Nitrogen as NITRATE (NO3
-) : Nitrate reductase.
 Nitrogen as NITRITE (NO2
-) : Unstable and gets reduced nitrate.
 Nitrogen as AMMONIA: promotes algal blooms, toxic.
 References: https://www.who.int/water_sanitation_health/dwq/chemicals/nitratenitrite2ndadd.pdf
 http://www.who.int/water_sanitation_health/dwq/ammonia.pdf

10. PHOSPHORUS
 Phosphorus is an element which is associated with Eutrophication
and eventual anoxia of water bodies.

11. REASONS FOR EFFLUENT TREATMENT
 Environmental Concerns.
 Economic concerns: Recycling of Water.
 Regulatory concerns: Compliance.

12. EFFLUENT TREATMENT PLANT (ETP)
INFLUENT EFFLUENT
SLUDGE

13. STAGES
1. Preliminary
2. Primary
3. Secondary
4. Tertiary (Advanced)

14. BIOLOGICAL
PHYSICAL
CHEMICAL

15. STAGE I: PRELIMINARY
 Screening.
 Sedimentation.
 Clarification.

16. STAGE 2: ADJUSTMENT OF PH
 Dosing with Acids or Alkalis to neutralize pH.
 Addition of flocculating agents: Aluminum Sulphate / Ferrous
Sulphate

17. CONSIDERATION DURING PRE-TREATMENT
 The effluents do not have a uniform composition at all the time; the pH will
vary time to time.
 Effluents are stored from 8 to 12 hours in the equalization tank resulting in a
homogenous mixing of effluents and helping in neutralization.
 It eliminates shock loading on the subsequent treatment system.
 Continuous mixing also eliminates settling of solids within the equalization
tank.
 Reduces SS, TSS.

18. STAGE 3: SECONDARY TREATMENT LEVEL
 Aerobic: Production of CO2, Biomass
 Anaerobic: Production of CH4, Biomass

19. ACTIVATED SLUDGE PROCESS
Primary Effluent
CLARIFIER
SECONDARY EFFLUENT
CENTRIFUGE: Sludge thickener

20. AERATION TANK
 The water is passed like a thin film over the different arrangements
like staircase shape.
 Dosing of Urea and DAP* is done.
 Water gets direct contact with the air to dissolve the oxygen into
water.
 BOD & COD values of water is reduced up to 90%.
*DAP = DI-AMMONIUM PHOSPHATE

21. CLARIFIER
 The clarifier collects the biological sludge.
 The overflowed water is called as treated effluent and disposed
out.
 The outlet water quality is checked to be within the accepted limit
as delineated in the norms of the Malaysian Standards.

22. SLUDGE THICKENER
 The inlet water consists of 60% water + 40% solids.
 The effluent is passed through the centrifuge.
 Due to centrifugal action, the solids and liquids are separated.
 The sludge thickener reduces the water content in the effluent to 40% water + 60% solids.
 The effluent is then reprocessed and the sludge collected at the bottom.
 Drying beds: Primary and secondary sludge is dried on the drying beds.

23. STAGE 4: TERTIARY TREATMENT
 Clarification: Addition of Aluminum Sulphate.
 Sterilization: Treatment with Chlorine / UV.
 Removal of Chlorine with Sodium Bisulphite.

24. STAGE 1
PRELIMINARY
TREATMENT
STAGE 2
PRIMARY
TREATMENT
STAGE 3
SECONDARY
TREATMENT
STAGE 4
TERTIARY
TREATMENT
BISULPHIT
E
CHLORINE
FILTRATION
ACID/ALKALI
ANAEROBIC/
AEROBIC

25. ROLE OF MICROBES IN EFFLUENT TREATMENT

26. FACTORS DETERMINING MICROBIAL POPULATIONS
 AGE OF THE SLUDGE
As bacteria first begin to develop in the system they grow singularly, in small clumps and chains. They are
very active with flagella and do not have a well-developed slime layer. The bacteria are disperse and do not
settle well. As the sludge is allowed to age, bacteria lose their flagella and accumulate more slime. The small
clumps and chains begin to stick together and form floc large enough to settle.
 CONCENTRATION OF OXYGEN
Aerobic bacteria require at least 0.1 - 0.3 mg/L of oxygen to survive. At least 2 mg/L of oxygen must be
maintained in the bulk fluid in order for the bacteria in the center of the floc to get 0.1- 0.3 mg/L of oxygen.
If not, the bacteria in the center will die and the floc will begin to break up.

27.  pH
It is the bacterial enzymes that are very pH dependent. Their optimal pH is between 7.0 and 7.5. Rapid
changes should be avoided.
 Temperature
Biochemical reactions are temperature dependent. Reactions are slower in colder temperatures so the
system will require more organisms to do the work. Reactions are faster in warmer temperatures
fewer bacteria are required to do the same job during the summer months.
 Nutrients
Bacteria require basic nutrients for growth (carbon, nitrogen, phosphorus as well as trace amounts of
sodium, potassium, magnesium and iron. All these are present in normal domestic sewage. Generally,
industrial wastes do not contain sufficient nutrients and must be supplemented.

28. PROTOZOA
 The presence of protozoa influences the clarity of water.
 Protozoa feed on other microbes.
 The quality of the effluent can be determined by observing the
population of protozoa.
 Types: Amoeba, Flagellates, Free-swimming ciliates, Crawling
ciliates, Stalked ciliates Naked Amoebae

29. SUCCESSION OF POPULATIONS
MetazoansRotifers
Stalked
Ciliates
Free
swimming
Ciliates
FlagellatesBacteriaAmoeba

30. AMOEBA
Presence of high numbers of Amoebae
 Shock load of BOD. This would make extra food
available that will allow them to compete.
 The presence of large amounts of particulate
matter. Amoeba favor particulates.
 Lack of oxygen. Amoebae move very slowly and
require less oxygen then other protozoa.

31. FLAGELLATES
Compete with bacterial for soluble food.
Flagellates peak in number while the soluble food
concentration is high and the number of bacteria is
still quite low. However, once the bacteria become
acclimated to the environment, they multiply much
faster than flagellates and will eventually out
compete them for soluble nutrients

32. FREE SWIMMING CILIATES
Feed on bacteria. Their presence indicates that the
process of treatment is nearing completion as most
of the bacteria have been consumed.
Require high levels of dissolved oxygen in order to
survive.

33. TRANSITION FROM FREE SWIMMING TO STALKED CILIATES
As the amount of nutrients decrease, food is limited and the bacteria begin to lose the flagella and form a
sticky slime layer that allows them to stick together to form floc. As floc particles enlarge, crawling ciliates
begin to dominate. Crawling ciliates have cilia on the under side of the body. The cilia are twisted together
to form “tufts” or legs that are used for crawling along the floc. Crawling ciliates graze on floc particles and
feed on the straggling bacteria on the edges of the floc. As the population of disperse bacteria decreases
and floc increases crawling ciliates out compete free-swimming ciliates because they can find food within
the floc and the free-swimming ciliates cannot.

34. STALKED CILIATES
Stalked ciliates compete with free living ciliates for
food. They form colonies by attachment to the
substrate. In mature sludge the number of heads on
a stalked ciliated indicates that degree of maturity
of the sludge.

35. ROTIFERS
Rotifers are an indicator of toxicity of the effluent
or sludge. They are susceptible to toxins and are the
first to die out in the event that the effluent
contains toxins.

36. METAZOANS
Metazoans are an indication that the sludge has
aged.
1. Tardigrades: sensitive to ammonia.
2. Nematodes.
3. Annelids.

37. TACKLING NUTRIENT DEFICIENCY
Often in industrial treatment systems and sometimes in municipal systems nutrient deficiency may occur.
This occurs when influent wastewater is deficient in nitrogen or phosphorus. Bacteria generally require 10
mg/L of nitrogen and 1 mg/L of phosphorus for every 100 mg/L of BOD that it consumes; a nutrient
ratio 100:10:1 (BOD: N: P). Slime bulking can result when there is a lack of sufficient nutrients for the
bacteria. Bacteria will also produce an excess amount of slime in the presence of significant amounts of
organic acids. These organic acids, usually produced under anaerobic conditions, can be recycled into the
plant when anaerobic digester supernatant is slug dosed into the recycle stream. If this is the case,
supernatant should be introduced into the system in smaller doses over a longer period of time. In some
cases, when sludge is held too long in the primary clarifier, organic acids produced in the sludge can enter
the aeration basin through the primary effluent.

38. MALAYSIAN REGULATIONS

39. HTTP://WWW.DOE.GOV.MY/EIA/WP-CONTENT/UPLOADS/2012/03/A-GUIDE-FOR-INVESTORS1.PDF

40. CONCLUSION
 Sewage treatment involves chemical, physical and biological processes.
 The biochemical process involves both aerobic and anaerobic processes.
 Anaerobic processes can be capitalized for the generation of energy via methanogenesis.
 A bioprocess engineer must be cognizant of the biological elements in an effluent treatment
plant.
 The Malaysian regulations govern the criteria for release of sewage in water bodies.

41. REFERENCES
 http://www.water-treatment.com.cn/resources/discharge-standards/malaysia_sewage-industrial-
effluent-quality-mal2509.pdf

42. THANK YOU
 For more information: kennethr@ums.edu.my