Application of Ozone to Municipal Sewage

International Conference Ozone and UV, April 3rd 2006

Wasser Berlin 2006 3

Application of Ozone to Municipal Sewage Treatment Hirofumi Takahara1, Shigeki Nakayama2 and Hiroshi Tsuno3 1, 2 Japan Ozone Association 1-3-9 Akasaka, Minato-ku, Tokyo 107-0052JAPAN 3 Graduate School of Engineering, Kyoto University Yoshida-honmachi, Sakyo-ku, Kyoto-city 6068501 JAPAN Key-word: Ozonation, Sewage treatment, Water reuse, Advance wastewater Treatment, Disinfection Abstract

In more than 60 sewage treatment plants in Japan, ozonation has been adopted to polish

effluents for the purposes of decolorization, removal of odor, disinfection, removal of organics, decomposition of micropollutants and so on. In this paper ,the state of arts in ozone application to municipal sewage treatment to polish effluents is discussed from the viewpoints of the application purposes , design and operation. In addition, typical examples ozone application are introduced. Introduction

The population covered with sewage treatment is 86,360,000 out of the total population of

126,687,000 in 2004. The coverage ratio of sewage treatment system is 68% in population, while adoption ratio of advanced treatment, including biological nutrient removal process, coagulation and sedimentation, sand filtration, and/or ozonation, is still only 13.2%. Comparison of coverage ratios of sewage treatment system among countries are shown in Figure1. Coverage ratios are shown to be comparable among these countries shown in the figure.

Amount of 13,200,000,000 m³/year has been discharged to rivers, lakes and coastal seas from sewage treatment plants. The effluent is now considered to be one of the important and stable water resources, especially in urban areas. The reuse of the effluent after advanced treatment has been attracting attention more and more. Ozonation is a promised and key technology for the advanced treatment for reuse.

In this paper, the state of the arts in ozone application to municipal treatment to polish effluent is discussed from the viewpoints of application purposes, design and operation. In addition, typical examples of ozone application are introduced.


4 Wasser Berlin 2006

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JAPAN SWEDEN HOLLAND GERMANY CANADA USA ENGLAND

Advanced Treatment

Sewage treatment

Figure 1 Comparison of coverage ratio of sewage treatment system among countries 1)

Overview of ozone application to sewage treatment in Japan

Effluent from advanced treatment process with ozonation has been mostly used for toilet flush, cooling, landscape, amenity and facilities-washing. In 1988, the first ozonation plant for polishing sewage effluent was constructed in Oita Treatment Plant to supply the water for the castle’s moat water in Japan. Then the number of ozonation plants constructed for sewage treatment has been increased year by year and reached to more than 60 in 2004 as shown in Figure2.

The application points of ozonation are mainly after coagulation and sedimentation, sand filtration and/or biofiltration of secondary effluent. And the most popular and important parameter for design and operation is ozone dosage, amount of ozone dosed per unit volume of treated water. The dosage ratio of ozonation in sewage treatment in Japan is shown in Figure 3. The ozone dosage ratio is 5-20 mg per litter of water, typically 10-15 mg ozone per litter of water.

Figure 2 Trend of numbers of installed ozonation plants 2)

0

2

4

6

8

10

12

5mg/l 5-10mg/l 10-15mg/l 15-20mg/l 20mg

Figure 3 Ozone dosage 3)

0

10

20

30

40

50

60

70

1988 1990 1992 1992 1994 1996 1998 2000 2002 2004



Examples of ozone application to sewage treatment 1) Tamagawa Joryu Plant, Tokyo

Recently, there have been gradually increased voices calling for water amenity improvement among local citizens. In response to this, Tokyo Metropolitan Government has been trying to revitalize streams with aim of improving water-side environment and creating a green network. For this purpose, the effluent from Tamagawa Joryu Plant supplied to Nobidome Stream firstly with water after sand filtration. However claim about odor and color problems occurred from the local citizens. So the ozonation process was introduced after sand filtration to solve these problems and resulted in success. The outline of the ozonation process and supplied water quality are shown in Table 1 and Table2, respectively. Ozonation also offers better contribution to security against pathogenic organisms.

Table 1 Outline of Tamagawa Joryu ozonation process 4)

Item Specification Capacity 43,200m3/day

flow Secondary effluent +Sand filtration +PAC + ozonation PAC injection PAC dosage 10-15mg Tank Volume 14m3 2 tanks

Ozonation Ozone dosage 5-10mg/l Ozone generator 10kg/h ,diffuser Ozone

decomposition Activated Carbon Volume 4320kg

PAC Ozone generator Ozone decomposer Second effluent Treated Water

Sand filtration Ozonation Ozonation

Figure 4 Ozonation Plant Flow 4)

Table 2 Water quality of treated sewage (Tamagawa Joryu Treatment Plant) 4)

Odor Color(CU) phosphorus SS COD C-BOD PH Turbidity Raw water 40 20 1.72 3 15 4 7.0 2

Sand filtration 22 12 0.35 1 10 1 7.0 Below 1

ozonation 18 8 0.41 1 10 2 7.2 Below1



2) Kisshoin Treatment Plant ,Kyoto Kisshoin sewage treatment plant receives a large amount of wastewater from dyestuff industries and suffered from color and COD problems. Then ozonation process was introduced after oxygen activated sludge process for removal of color and reduction of COD concentration as well as disinfection. The outline of the ozonation process and water quality of the effluent is shown in Table 3 and Table 4, respectively. Ozone treated water quality clears the guideline of discharged water quality.

Table 3 Outline of ozonation process (Kissoin Treatment Plant) 5)

Capacity 120,000 m3/day ( Line A 40,000 m3/day ,Line B 80,000m3/day Amount of ozone generation : 22.5kg/h 3 number Ozone concentration : :110g/Nm3, diffuser ,Contact time: 11.3 min Ozone dosage : Max 20mg/l

Ozonation

Power consumption : 0.1kw/ m3

Table 4 Water quality of treated sewage (Kisshoin Treatment Plant)5)

PH BOD C-BOD COD SS T-N NH4-N T-P Color Raw Water A 7.3 91 63 84 21 2.8 30 Raw Water B 7.6 230 190 204 21 4.0 77 SedimentaionA 7.2 60 49 43 19 12 1.6 31 SedimentaionB 7.3 64 57 52 21 13 1.8 37 Treated WaterA 7.1 3.1 2.0 8 2 5.1 0.3 0.33 16 Treated WaterB 6.5 5.1 2.3 11 3 13 2.6 0.7 20 Discharged 6.8 5.1 3.6 8.3 2 8.4 1.5 0.46 5.9 (2004)

3) Shibaura Water Reclamation Center, Tokyo Tokyo Metropolitan government has been trying to expand the use of the reclamation water. The new reclamation plant using microfiltration membrane(MF) together with ozone (see Figure5) was constructed at Shibaura Water Reclamation Center and began to operate in April, 2004. The treatment capacity is 4300 m³/day. The reclamation water is supplied to redeveloped area in Shinagawa, Shiodome and Osaki as toilet flashing water and water for environmental improvement. MF can keep high filtration flux as 5m³/(m² d) and stable operation without chemical cleaning by combination with ozonation. The water quality of treated sewage is shown in Table 5. The reclamation water obtained has a quality without color, odor and suspend matter. And it is excellent in security against pathogenic microorganisms.



Sewerage secondary effluent water ↓

Pre ozone process ↓

Bio filtration process ↓

Ozone oxidization process ↓

Micro filtration process ↓ �dosing disinfectants�

Reclamation water Figure 5 Flow sheet of the developed reclamation of reclamationsystem6)7)

. 4) Konantyubu Sewage Treatment Plant

Ultra advanced sewage treatment plant was constructed and has been operated from 2005 in Konantyubu Sewage Treatment Plant to preserve the quality of Lake Biwa.The treatment process is composed of biological nutrient removal with coagulation, sand filtration, ozonation and bio-activated carbon filtration. The treatment capacity is 6,500 m³/d. Water quality of effluent before and after of additional ozonation and bio-activated carbon is shown in Table 6.

Table 5 Water quality treated sewage6)7)

Treatment process Item

Raw water (Secondary

effluent) Bio-filtration Ozone MF membrane

Water quality standard values

for recreation reuse

T-BOD (mg/L)

16 4.4 2.3 2.1 <3

COD (mg/L)

11 8.2 5.9 5.7 �

Heterotrophes (CFU/mL)

4.4E+04 2.6E+03 0 0 �

E-Coli (CFU/100mL)

1.8E+05 1.5E+04 0 0 <50

Fecal coliform (CFU/100mL)

6.5E+04 1.2E+03 0 0 �

NH3-N (mg/L)

10.8 2.97 3.34 3.55 �

NO2-N (mg/L)

1.66 0.84 0.44 <0.03 <0.03

NO3-N (mg/L)

4.9 14.7 16.3 16.3 �

Color (C.U.)

31 17 8 1 <10

1) These numbers are the average value from 30 analytical tests (experiment durations�2000.4�2001.2)

2) Standard values are quoted from the manual of water quality management for landscape irrigation and



Table 6 Water quality of treated sewage (Konantyubu Sewage Treatment Plant)8)

Before After COD �� COD T-N T-P 6.0 6.0 0.05

3.0 3.0 0.02

Conclusion Up till now more than 60 ozonation plants have been constructed in Japan. The plants numbers in constriction and planning will be increased in the future, especially where sewage effluent is to be reused and higher water quality is required. References 1) Ministry of Land, Infrastructure and Transport, Current State of Sewerage Treatment in Japan,

2004 2) JOA, Ozone News in Japan Vol 3-Vol 56 3) Japan Ozone Association, The Study of artificial reuse water using ozonation 28-33, 1997 4) H. Akimoto, Ozone Application to municipal treatment in the case of Tamagawa Jyoryu treatment

plant, JOA 1st ozone technology seminar 123-143, 1991 5) Kyoto-city sewerage bureau, leaflet of Kisshoin Sewage Treatment Plant, 2004 6) K. Kitamura, Application of ozone and ozone resistance micro filtration membrane for the reuse of

secondary effluent, JOA 22nd Ozone technology seminar, 1-5, 2004 7) T.Onitsuka, S Takeda, Application of ozone and ozone resistance micro filtration membrane for the

reuse of secondary effluent, Ozone News Vol33No4, 21-24, 2005 8) H. Kano, Ozone application to municipal sewage treatment- Ultra advanced sewage treatment, the

joint seminar by Japan Ozone Association and Japan Society on water environment, Sep, 2005

Application of Ozone to Municipal Sewage

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