Mitsubishi Heavy Industries Technical Review Vol. 51 No. 3 (Sep. 2014)
14Development of Advanced Wastewater Treatment
and Reclamation System

TAKESHI TERAZAKI

KOSUKE SHIGIISHI*1*2

HIROSHI NAKASHOJI

HOZUMI OTOZAIHIDEO SUZUKI*4*2*3

HIROYUKI KAWAMOTO*5

Recycling and the reuse of industrial wastewater has always been an important need forwater-scarce regions such as Singapore. This will also be beneficial to emerging countries such asIndia, China, the Middle East, etc., as it will not only provide water to meet increasing population
growth, but also reduce environmental pollution. With that goal in mind, a demonstration plant totest industrial wastewater treatment processes was set up in Singapore in 2013. This test plant issituated at the Jurong Water Reclamation Plant (JWRP), where wastewater from the Jurong
Industrial Estate will be treated. In this test, Mitsubishi Heavy Industries Mechatronics Systems,Ltd. (MHI-MS) has demonstrated the stability of the treatment process, where the treated water
has a constant CODCr level of 100 mg/l or less. In addition, high water recovery ratios of 60%
using a reverse osmosis (RO) membrane system and 75% using a capacitive deionization systemwere obtained in spite of the highly variable qualities of the incoming industrial wastewater. This
report presents the results of this demonstration test, as well as future plans for testing.

|1. Introduction
As city functions develop in emerging countries such as India, China, Singapore, as well as
those in the Middle East and Africa, environmental pollution resulting from the discharge ofuntreated urban wastewater has become a serious issue, giving rise to the necessity for wastewater
treatment in urban areas. Emerging countries also face environmental pollution resulting from thedischarge of untreated wastewater, giving rise to the necessity for wastewater treatment. In order tomeet such needs, it is necessary to combine advanced water reclamation treatment technologies
with existing wastewater treatment technologies.
Cooperating with Mitsubishi Heavy Industries, Ltd. (MHI) and Mitsubishi Heavy Industries
Engineering & Services Private Ltd. (MIES), MHI-MS Installed a demonstration test plant with athroughput of 48 m3/d to process untreated industrial wastewater at the Jurong Water Reclamation
Plant (JWRP) owned by the Public Utilities Board (PUB) of Singapore. The demonstration testcommenced in September 2013.

|2. Overview and processes of demonstration test of wastewater
treatment at industrial park
Figure 1 is a flow diagram of the wastewater treatment system. Despite the highly variable
qualities of the incoming industrial wastewater, the system can operate steadily and even at a highwater recovery ratio (i.e., the quantitative ratio of the obtained desalinated water to the wastewater). It*1

Manager, Water Treatment System Engineering Section, Environmental Plant Department, Plant Facilities Division,
Mitsubishi Heavy Industries Mechatronics Systems, Ltd. (MHI-MS)*2

Water Treatment System Engineering Section, Environmental Plant Department, Plant Facilities Division,
Mitsubishi Heavy Industries Mechatronics Systems, Ltd.

*3

Chief Staff Manager, Major Infrastructure & Water Solution Project Management Department,
Chemical Plant & Infrastructure Division, Energy & Environment*4

Chief Staff Manager, Major Infrastructure & Water Solution Project Management Department,*5

Water Solution Business Unit, MITSUBISHI HEAVY INDUSTRIES ENGINEERING & SERVICES PRIVATE LTD. (MIES)Mitsubishi Heavy Industries Technical Review Vol. 51 No. 3 (Sep. 2014)15

consists of two main processes: wastewater treatment and desalination. In order to maintain thestable operation of the desalination treatment process, it is necessary to maintain the stable operationof the upstream wastewater treatment process. This in turn will ensure a constant supply ofindustrial water and NEWater (a brand name that collectively denotes reclaimed water of highquality, produced by purification treatment using advanced desalination technology). Below is an
overview of the treatment processes.

Figure 1

2.1

Flow diagram of wastewater treatment system at industrial park

Wastewater treatment process

Wastewater treatment is mainly comprised of two processes; the pre-treatment systemprocess and the biological treatment process.
(1) Pre-treatment system process
The main purpose of the pre-treatment system process is the removal of inhibitors prior
to biological treatment. The methods used for removal/treatment are chosen appropriately
depending on the target substances. In order to prevent the disruption of the subsequentbiological treatment, floatable components (e.g., oils and solvents) are separated through aprocess of floatation using oil separators, while heavy metals (e.g., Cu, Zn and Ni) andsuspended solids (SS) are removed by sedimentation techniques. The high-speed sedimentation
system used in this process (Figure 2) is a proprietary technology of MHI-MS. It is highly
compact and exhibits excellent capacity for SS removal compared with conventional
sedimentation systems.

Figure 2

High-speed sedimentation equipment

Mitsubishi Heavy Industries Technical Review Vol. 51 No. 3 (Sep. 2014)16(2) Biological treatment process
The biological treatment process is performed mainly to remove organics (based on thechemical oxygen demand (COD), biochemical oxygen demand (BOD), etc.) contained in thepre-treated water (inhibitors have been removed prior to the biological process).
In this process, two types of biological treatment methods are used: bio-film reactor (BFR)
and membrane bioreactor (MBR). These treatment systems are illustrated in Figure 3. BFR is a
fixed bio-film process in which organics are aerobically treated through the use of oxygen andnutrients by microorganisms attaching to the packing surface of the fixed bed in the tank, i.e., thedecomposition of organics. Because of this attachment to the packing surface, the bacterial flora
is unlikely to change and a certain number of bacteria can be maintained. Thus, BFR is atreatment method that has the capability to adhere to the change in load. On the other hand,
MBR is an aerobic treatment process in which biological flocs, i.e., activated sludge, are used todecompose the organics. This treatment retains the sludge, i.e., mixed liquor suspended solids(MLSS) at levels higher than the standard biological treatment, i.e., activated sludge treatment, byadopting microfiltration (MF) instead of sedimentation separation. This makes it possible tooperate the system under high organic volumetric loading, which results in the reduced size of thebioreactor.
This process is designed to ensure the stable treatment of the highly variable qualities ofincoming industrial wastewater by combining BFR, which has the capability to adhere to thechange in load, with MBR, which can operate under high-load conditions.

Figure 32.2

Biological treatment processes (BFR and MBR)

Desalination process

In the desalination process, two treatment methods have been adopted: the RO membrane
system and the capacitive deionization system.
(1) RO membrane system
The RO membrane system is a method that is technically established. An RO membrane
is a semi-permeable membrane with a porous diameter of less than 1 nm. Water molecules willpass through the RO membrane through the application of pressure greater than the osmoticpressure, allowing pure water through while holding back the majority of contaminants such asions, salts and low-molecular organic compounds (Figure 4).
(2) Capacitive deionization technology
Capacitive deionization technology is known as a next-generation desalination
technology that is still under development. It uses a pair of electrodes with large specificsurface areas to create a small electrical field to deionize the water. The area between theelectrodes is filled with the water to be desalinated and anions are adsorbed onto the anode andcations are adsorbed onto the cathode (Figure 5).

Mitsubishi Heavy Industries Technical Review Vol. 51 No. 3 (Sep. 2014)
17Figure 4 RO membrane desalinationequipment

Figure 5 Capacitive deionizationequipmentThis process is designed to obtain the stable operation of the desalination system anddetermine the maximum ratio of water recovery using treated water with certain qualities that has
undergone the aforementioned wastewater treatment process.

|3. Demonstration test results of wastewater treatment at industrial
park
Shown below are the test results of the demonstration wastewater treatment plant.

3.1

Wastewater treatment process(1) Evaluation of high-speed sedimentation system performance
The SS levels in the industrial park wastewater fluctuate significantly, while the designed
level is 300 mg/l. In spite of the severe test conditions with a continuous inflow of wastewaterthat substantially exceeds the designed SS level of 300mg/l, an SS removal rate of more than
80% has been demonstrated under the influence of chemical dosing. The injection rate for theflocculant, FeCl3 is 100 mg/l and that of the polymer coagulation aid is 2 mg/l (Figure 6).
The linear flow velocity (LV) of the high-speed sedimentation system compared with aconventional sedimentation tank is approximately 8-fold, and therefore the installation area ofthe sedimentation tank can be expected to decrease to nearly one-eighth.

Figure 6

SS removal performance of high-speed sedimentation system(2) Evaluation of BFR Performance
Although the CODCr (dichromate chemical oxygen demand test used to measure theorganic matter in the water) levels in the pre-treated water fluctuate considerably, they are equal
to or below the designed level (1,000 mg/l). This occurred when BFR operates below thedesigned load condition of 1.5 kg-CODCr/m3.d (volumetric loading per biofilm).
As shown in Figures 7 and 8, BFR is able to produce treated water with a CODCr level of
300 mg/l or less within a load fluctuation range of 0 to 1.5 kg-CODCr/m3.d, thus demonstrating
its extensive removal capability over a wide range of volumetric loading.

Mitsubishi Heavy Industries Technical Review Vol. 51 No. 3 (Sep. 2014)18

Figure 7 Relationship between CODCr space loading and quality oftreated water (BFR)

Figure 8 Relationship between CODCr space loading and removed
CODCr quantity (BFR)(3) Evaluation of MBR Performance
Similar to BFR, under an operating condition of the designed load (space loading pertank capacity) of 2.4 kg-CODCr/m3.d, MBR has demonstrated the capability to remove CODCr.
Treated water produced by MBR has a CODCr level of 100 mg/l or less (which is the minimum
specification for COD level for reclaimed water in Singapore) (Figure 9).

Figure 9 Relationship between CODCr space loading and quality oftreated water (MBR)Mitsubishi Heavy Industries Technical Review Vol. 51 No. 3 (Sep. 2014)19

The removal of CODCr tends to increase as the volumetric loading rises under theoperating condition of a space loading range of 0 to 2.4 kg-CODCr/m3.d. This indicates its
removal capability to produce treated water of satisfactory quality even under high loads(Figure 10).

Figure 10 Relationship between CODCr space loading and removed
CODCr quantity (MBR)

Therefore, it has been demonstrated that by combining BFR and MBR (i.e., excellent load
following capability and operability under high loads, respectively), stable biological treatment
operation is possible. Furthermore, MBR can produce good quality treated water to be fed
continuously to the downstream desalination process.

3.2

Desalination process(1) Evaluation of RO membrane system performance
Although it is not easy to realize it, the recovery ratio can be increased to 60% as
described in Section 3.1 where the upstream wastewater treatment process can be maintained
under continuous stable operation. As shown in Table 1, the quality of RO permeated watersatisfies the stringent criteria of NEWater in Singapore, which indicates the satisfactory
performance of the RO system.
Table 1
ItempH
Ca2+
Mg2+
NH4+
M-Alk
ClPO43FTDS
Conductivity
BOD5

Quality of RO permeated water and NEWater quality control criteria

Unit－mg/Lmg/Lmg/L as Nmg/L as
CaCO3mg/L
mg/L
mg/L
mg/L
μS/cm
mg/L

Water recovery ratio

60％

RO feed water
7-830-55
30-40≤5RO permeate water
6.5-7.5
≤1
≤0.5
≤0.4

NEWater quality criteria
7.0-8.5(Total Hardness)＜5mg/L as CaCO3＜0.5100-280

5-10＜50 *1600-800≤615-35
1 700-2 300
2 800-3 400
0-25

≤17
≤1.5
≤0.4
40-80
70-140≤3＜20 *2－＜0.5＜90 *3＜150 *4－*1 : Total Alkalinity*2 : Applicable when 350 < Cl- in RO feed water ≤550
*3 : Applicable when 1,000 < TDS in RO feed water ≤ 1,330*4 : Applicable when 1,580 < RO feed water Conductivity ≤ 2,100(2) Evaluation of capacitive deionization system performance
Continuous stable operation of the upstream wastewater treatment process has allowed
the capacitive deionization system to achieve a water recovery ratio of 75%. Although thetreated water of the capacitive deionization system is unable to meet the NEWater quality
criteria, it is able to meet the industrial water quality criteria (Table 2).

Mitsubishi Heavy Industries Technical Review Vol. 51 No. 3 (Sep. 2014)20

Table 2

Quality criteria of capacitive deionization water and industrial water

Item

UnitpH
Ca2+
Mg2+
NH4+－mg/Lmg/Lmg/L as N
mg/L asCaCO3mg/L
mg/L
mg/L
mg/L
μS/cm
mg/L

M-Alk-Cl
PO43FTDS
Conductivity
BOD5

Water recovery ratio

Feed water ofcapacitive deionization
7-830-55
30-40≤5Capacitivedeionization water
6.5-8
≤10
≤10
≤1

Industrial water quality
criteria
6.5-7.2(Total Hardness)
100-250mg/L as CaCO3＜5100-280

75

30-80

600-800≤615-35
1 700-2 300
2 800-3 400
0-25100-350≤45-20600-900
750-1 050
≤5100-500
1-4－350-1 300
600-1 600
1-575％|4. Future test schedule
The future test plans are summarized below.
(1) Cost reduction for operation and facilities
Cost reduction for the operation and facilities of the system will be carried out by a few
methods such as optimizing the chemical consumption of the high-speed sedimentation systemand examining the influence of an increase in flux (the amount of permeated water per unit
membrane area) on the performance of the biological treatment process (MBR).
(2) Determining the optimum operating condition of desalination system
The stable operation of an RO membrane system with a water recovery ratio of 60% has
been demonstrated. We will optimize the chemical consumption for the RO system. The
maximum water recovery ratio in the capacitive deionization system will be determined bychanging the operating parameters while maintaining stable operation.

|5. Conclusion
At the Jurong Water Reclamation Plant, a demonstration system with a throughput of 48
m /d used to process untreated industrial wastewater has been installed. The demonstration testcommenced in September 2013 to treat wastewater from the Jurong Industrial Estate. The purpose ofthis plant is to demonstrate the viability of advanced water treatment/recycling technology. In thisdemonstration test, despite the highly variable quality of the industrial wastewater, the system wasable to operate stably. In addition, a higher water recovery ratio was achieved. For future testing,
we will study the maximum water recovery ratio of the capacitive deionization system, and at thesame time attempt to further reduce operational and facility costs to make the technology practicalfor commercial purposes.
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