This document provides a literature review on factors affecting dissolved oxygen (DO) and oxygen uptake rate (OUR) profiles in activated sludge models. It discusses that the International Water Association's Activated Sludge Model No. 1 (ASM1) is commonly used to model microbial kinetics in wastewater treatment and includes DO and OUR. Parameters in ASM1 are typically based on local influent/effluent quality and operational conditions. Studies analyze DO and OUR profiles in detail to improve oxygen control systems for energy savings and effluent quality. The document also reviews guidelines for wastewater treatment in Malaysia and concludes that ASM1 simulations can provide input for aeration control systems to meet these guidelines.

1. Journal of Multidisciplinary Approaches in Science 9, Issue 1 (2019) 1-8
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Journal of Multidisciplinary Approaches
in Science (JMAS)
Journal homepage: https://jmas.biz/index.php
ISSN: 2652-144X
Evaluation on Affecting Factors on Dissolve Oxygen and
Oxygen uptake Rate Profiles by Activated Sludge Model
Simulation – A Review
Siti Aishah Binti Mokhtar*,1 & Masafumi Goto1
1 Malaysia-JapanInternationalInstituteofTechnology,UniversitiTeknologi Malaysia,81310,Johor Malayia
ARTICLE INFO ABSTRACT
Article history:
Received19May 2019
Receivedin revisedform 5 September 2019
Accepted 11 September 2019
Availableonline 18September2019
A literature surveyregardingthe dynamic mathematical modelof the activatedsludge
process based on IWA's ASM1 (International Water Association; Activated Sludge
Model No 1) has been established. It has been discussed that the microbial kinetics
model is basedon the ASM1 structure, modifiedto include dissolve oxygen (DO)and
oxygen uptake rate (OUR). It hasbeenshown throughliterature that parameter values
are based on the typical influent and effluent water quality indices, and operational
conditions in Malaysia. OUR and DO profiles are analyzed in various literatures in
detail, for the efficacy of DO control system in terms of energy savings and effluent
qualities.
Keywords:
ASM, OUR, STELLA, DO Copyright © 2019 JMAS - All rights reserved
1. Introduction
71% of the earth surface is covered by water and the remaining is land, in which water is the major
and most important component of the environment that sustains the lives and ecosystem on the
earth. Under the current circumstances of rapidly increasing world population, and industrialization
and urbanization, maintaining both qualities and quantities of safe water resources for a sustainable
world is an urgent issue to be addressed globally.
Wastewater by definition means water that has been contaminated by inorganic and organic matters
from the sources including industries, commercial facilities,houses and any other socialactivities [1]–
[5]. A wastewater, or known as effluent from a point source and non-point source, can overload
environment if released to the receiving body of waters without proper treatment.
Corresponding author.
E-mail address: Siti Aishah Binti Mokhtar (saishah9518@gmail.com)
Open
Access

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List of Abbreviations
Aside from toxic materials, major concern on wastewater is its organic contaminants, which are
commonly measured and expressed by biochemical oxygen demand (BOD) and chemical oxygen
demand (COD). Therefore, the essential function of wastewater treatment is to reduce the BOD and
COD in the raw wastewater. The strategies of new approaches to estimate the BOD5 and their
required analysis durations are shown in Figure 1.
Figure 1. (A) The strategies of new approaches to estimate the BOD5 and (B) their required analysis
durations [6]

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BOD is the measure of the biochemically oxidizable material present in the wastewater, which is
expressed by the term of the amount of oxygen needed to oxidize microbiologically. It also can be
expressed as the amount of oxygen needed to oxidize the organic carbon present in a wastewater by
the microbial activities called as respiration [7], [8]. Meanwhile, COD is another standard method of
evaluating the amount of oxygen depletion as a result of chemical reaction. The COD test uses a
strong oxidizing chemical (potassium dichromate or potassium permanganate) to chemically oxidize
the organic material in wastewater, which determines the amount of total organic material in the
wastewater. The COD is normally 1.3 to 1.5 times greater than the BOD of the same sample [9]–[11].
1.0 ASWTP
Activated sludge wastewater treatment plant (ASWTP) has been used for about a century as one of
the treatments for wastewater. There are several considerations which are needed to design ASWTP
and its mathematical microbial kinetic model for a better performance and efficientenergy utilization
sewage treatment plant, which is the Activated Sludge Models no 1 (ASM1) from IWA, DO, OUR and
CFSTR.
1.1 ASM1
IWA, which was founded in 1999 from the previous International Water Supply Association,
established in 1947, and the International Association on Water Quality, established in 1965, has
formed task groups to develop practical mathematical models of activated sludge processes for
applications in design and operation of sewage treatment plants, (STPs). The first and the most
fundamental model that was finalized and released in 1987 is the ASM1 [12], [13].
The objectives of the ASM1 task group were as below;
a. To review the existing mathematical models then available.
b. To reach a consensus concerning the simplest mathematical model with a capability
of realistically predicting the performance of single sludge systems carrying bi-
substrate model of carbonaceous substances.
ASM1 is a dynamic model system of wastewater treatment and it has the simplest mathematical
expressions with a capability of realistically predicting the performance of single sludge system
carrying out the substrate model to describe ASM1 effectively, several steps are taken into
considerations [14]–[16]. These steps are summarized as follows.
(a) Characteristics of the effluent
(b) Hydraulics of each tank
(c) Organisms growth and decay
(d) Hydrolysis of different substrates of the influent
(e) Carbonaceous, nitrogenous and phosphorus removal mechanisms
(f) Sludge clarification and thickening mechanisms

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1.2 DO
DO is a free, non- compound oxygen (oxygen that is not bonded to any other element) present in the
water and it is an important parameter to conduct an assessment for the water quality. This is due
to its ability to influence the organisms living in the water for respiration. Furthermore, microbes
such as bacteria and fungi required the DO to decompose organic material at the bottom of the water
body and it was called as nutrient recycling. However, the oxygen at lower levels will be used at a
quicker rate when there is an excess of decaying organic material resulting from dying of algae and
other organisms, in a body of water of no turnover which is also known as stratification.
Dissolved oxygen change for every species of organisms that live in that aquatic habitat. Canadian
habitats can hold up to 5.6 mg/l oxygen requirement and as low as 0 mg/l oxygen requirement for a
period of time. The mean requisite for dissolved oxygen by ostracods falls within a very narrow
margin of 7.3–9.5 mg/l [17]–[19].
Oxygen have low solubility in the water and it decrease as temperature and salinity increase. A
tropical freshwater fishpond at sea level will be in 100 percent saturated by oxygen at 35°C with the
DO 6.949 mg/l. Furthermore, for every 1,000 m of altitude, the maximum saturation concentration
of DO must be reduced by 12 percent. Oxygen diffusion to the surface water from atmosphere at the
rates of 1 to 5 mg/l. The photosynthesis of organism is the main source of oxygen which range to
about 5 to 20 mg/l daily and a fluctuation of DO are seen day-night observation with the minimal at
sunrise [20].
1.3 OUR
ASM1 is an aerobic process in which oxygen must be continuously supplied in order to achieve high
productivity. Oxygen is a vital component in the growth and metabolism of microorganisms, the OUR
from the surrounding air into the system(water) have to be properly understood. The main function
of a properly designed activated sludge system is to provide a controlled environment and a
concentration of nutrients. When there is higher stirrer speed, the coefficient of oxygen consumption
and yield of oxygen will decrease as the cell is damage from hydrodynamic conditions [21]–[26].
In the study of oxygen transfer and uptake rates during xanthan gum production, the DO
concentration should be maintained higher than 10% of saturation value. This is to ensure that the
microorganisms are not going to be damaged due to lack of oxygen in a stirred bio-tank reactor.
Measurement of different stage of biomass with the parameters of OUR and oxygen transfer rate
(OTR) at the microorganism growth-lag exponential and stationary stages gives an increase of OUR
result on growth phase and a constant decrease afterwards which confirm with the theory of death
of microorganism [27]–[30].
1.4 CFSTR
CFSTR is a reactor model in which the feed is stirred uniformly causing an assumption of no variation
or concentration gradients exist within the vessel. Theoretically, the output taken from the overflow
of the reactor will be identical with any output taken from inside the vessel. There is a continuous in-
flow of nutrient and continuous equal out-flow of nutrient, with the addition of microbial waste

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products and microbial cells. To describe CFSTR effectively, several parameters are in the
consideration [31]–[36];
(a) Flow rate
(b) Residence time
(c) Dilution time.
2.0 Guideline and Problem
The complete mathematical microbial kinetic model of ASM1 are modelled to produce a model
system that follow the guideline from Malaysia government. Therefore, the problem that is faced in
term of energy efficiency can be handled accurately while maintaining the result of effluent needed.
2.1 Electricity demands at sewage treatment plants
The process of wastewater treatment using the Activated Sludge model needed an aerobic condition
situation, in which, an aerator or a blower are needed for the microbial kinetics process to occur.
Table 1 shows that the electricity cost for aerator and blower was 32 % of the total operational cost
in 2013. Fraction of electricity cost in the total operational cost is expected to continue to increase
as more advanced treatment of sewage is demanded [37], [38].
Table 1. Indah Water Konsortium Environmental and Sustainability Cost Highlights [37]
Sustainability
Effort
Activities
Total Cost (RM million)
2011 2012 2013
Operation and
Maintenance
(O&M)
Operation Planning
313.41 347.0 397.90
Treatment Plant O&M
Sewer Maintenance
Desludging
Laboratory Services
Bio-solid treatment &
Disposal
Electricity (Aerator&
Blower)
168.3 179.3 187.44
2.2 Guideline from the Department of Environment (DOE) Malaysia
The Department of Environment (DOE) is the government authorities that will determined and
regulate the water treatment company to follow the guidelines needed for different type of stream
water. The requirement was regulated to about 20 mg/l for the discharge at the upstream and 50
mg/l for downstream water body flow. Therefore, a lot of different type of treatment was made to
reduce the amount of BOD and COD before being discharge to the environment in Malaysia as refer
to Table 2, the Environmental Quality (sewage and Industrial effluents) regulation 1979, parameter
limits of standard A and B [39], [40].

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Table 2. Parameter Limits of Standard A and B [39]
Parameter Unit
Standard
A B
Temperature oC 40 40
pH value - 6.0-9.0 5.5-9.0
BOD5 at 20oC mg/l 20 50
COD mg/l 50 100
Suspended Solid mg/l 50 100
Mercury mg/l 0.005 0.05
Cadmium mg/l 0.01 0.02
Chromium/ Hexavalent mg/l 0.05 0.05
Arsenic mg/l 0.05 0.10
Cyanide mg/l 0.05 0.10
Lead mg/l 0.10 0.50
Chromium/ Trivalent mg/l 0.20 1.00
Copper mg/l 0.20 1.00
Manganese mg/l 0.20 1.00
Nickel mg/l 0.20 1.00
Tin mg/l 0.20 1.00
Zinc mg/l 2.00 2.00
Boron mg/l 1.00 4.00
Iron (Fe) mg/l 1.00 5.00
Phenol mg/l 0.001 1.00
Free Chlorine mg/l 1.00 2.00
Sulphide mg/l 0.50 0.50
Oil and Grease mg/l undetectable 10.00
3.0 Conclusion
Sewage treatment is considered as the largest industry in terms of the raw material treated, which is
sewage. Modern control system relied heavily on adequate process model which includes the math
model based on the microbial kinetics (ASM 1). The model established can simulate the behaviours
of the DO and OUR under typical Malaysian conditions, which in turn can provide the input for
aeration control system of the activated sludge plant in Malaysia.
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