Advanced treatment of domestic wastewaterusing a combination of Johkasou and simple BGF ditch- Examination of production and safetyof vegetables and fruits -11th August, 1996

Dr. Yasuo Ozaki
Professor Emeritus, Akita Prefectural University

１．Purpose of the Research
The presenters developed a BGF ditch (Biogeofilter ditch) that combines usefulplants and natural mineral filter media in order to recycle fertilizer components
in Johkasou effluent. We have conducted research on combination of usefulplants etc., to obtain stable treated domestic wastewater quality throughout theyear.1)After retiring, I installed a simple BGF ditch at my home in Tsukuba City inNovember 2016 using materials that could be purchased at DIY store in order tospread the utilization of BGF ditch, and conducting advanced treatment tests forJohkasou effluent using vegetables, fruits, flowers, etc. We are considering forvegetables and fruits that are suitable for this system, and considering annual
cultivation management methods.2),3)
I investigated the results of surveys of 2018 and 2023, the safety of harvested
vegetables and fruits by referring to the International Organization forStandardization's Guidelines for Irrigation Use of Treated Wastewater4） (ISOGuidelines). In this presentation, I will report the summary of the results.

２．The prototype of BGF ditch and its feature
Picture. 1

Water
OutletW；59cm, L；5.46m, H；31.5cm
Water
Inlet

Prototype simple BGF ditch①Prototype simple BGF ditch： Create a ditchusing waterproof plywood and rubber sheet.
Filled with pumice to a height of 28 cm.
Picture. 2

Water
Inlet

② Effluent inlet； The waterway was filledwith pumice to a height of 28 cm. （upperpart； Particle size 2～6m, bottom part；
Particle size 6～11mm)④Feature： The inflowing effluent from a Johkasou
flows down through the pumice stone and flows fromthe outlet through the PVC pipe into the biotope pond.
Therefore, effluent does not rise to the surface layer ofthe ditch.
Picture. 3
WaterOutlet③Water outlet： The water depth was set to 17cm.
Runoff water passes through PVC pipes and flows into
the biotope pond.

３．Method of the research
Ditch B

☆ Advanced treatment type Johkasou(CENeco-5 type) installed in October 2016.

OutletBiotopepond ①Ditch A

Control panel
JohkasouEffluent

OutletFlowmeter
Disinfection tank

JohkasouEffluent
storage tank(570 L)
DrainagechannelFigure. 1 An advanced treatment system for domestic wastewater that combinesa Johkasou, a simple BGF ditch, and a biotope pond.
• Simple BGF ditch：W；59 cm, L；5.46 m, H；31.5 cm, water depth 17 cm,capacity of retention water: approx. 302 Ｌ• Pumice filling height ： 28 cm. Fill 450 L of small grains (2 to 6 mm) on top of450 L of medium grains (6 to 11 mm).
• Biotope pond water capacity: approx. 570 L, water area: approx. 2.5 m2

〇 Operation and Maintenance of Johkasou and simple BGF ditch
A fixed amount of Johkasou effluent (see Table 1) is supplied to two lines of simple BGF
ditch by a submersible pump every day under timer control (e.g., supplied for 10 minutes,stopped for 50 minutes).

Table. 1 Johkasou operation management method in 2018 and average supply
amount of Johkasou effluent (L/day)survey period

Ditch A（Flowers/Conifer）

Ditch B(vegetables/fruits)

Johkasou operation management method

9 April to 17 April

161

160

5-June：Reduce circulating water volume (6.5Ｑ→2.5Ｑ)

18 April to 17 July

258

268

17-July：Continuous aeration → changed to intermittent
aeration
12-September： Intermittent aeration → return tocontinuous aeration
2-October：Increase circulating water volume (2.5Ｑ→6.5Ｑ)

18 July to 27
238
343
September
28 September to236
238
18 March
survey period ：9-April, 2018 to 18-March, 2019,〇 Water sampling and Analyzing

Q: Inlet water of Johkasou (L/day)• Water sampling was conducted at six points: the treated water storage tank, the midpoint
and outlet of both A&B ditches, and biotope pond ②.
• Sampling was conducted 2-3 times a month. Analysis items include COD, SS, nitrogen, andphosphorus. Water sampling will be postponed if rainfall exceeds 10 mm in the three days
before water sampling.

Ditch B ( vegetable )OutletWater convolvulus (4Asparagus bean (5 plants)
plants)Molokheiya (4 plants)
Leaf lettuce
Taro
Water convolvulus (4Tomato (3 plants)
plants)

B4B3

Leaf lettuce

Passion fruit (2 plants)

Inlet

Basil (3plants)Tomato (1 plant)

Basil (5 plants)

Tomato (3 plants)

Melon (2 plants)
Edible chrysanthemum

B2

B1Ditch A (Flowers/Conifer)
OutletZinnia (2 plants)

Torenia (1 plant)

Petunia (4 plant)

Zinnia (2 plants)

Sunpatience (1 plant)

Gazania (2 plants)

Kochia (3 plants)

Lobelia (4 plants)

Bidens (1 plant)

Marigold (6 plants)

Dwarf sunflower (6plants)

Bidens (1 plant)

A4A3A2

A1

Inlet

Figure. 2 An example of planting vegetables and flowers in Ditch A and B(mid-June to September 2018)
Conifer planting location : AI; Red star, A2; Gold crest, A3,A4; Elegante sima

☆After harvesting the vegetables and flowers planted in each plot, thenext vegetables and flowers were immediately transplanted.

４．Research Results in FY 2018
〇 Growth status and harvested melons on July 9th

Ditch A

Leaf lettuce, Tomato(section B3)

Ditch B

Melon (section B1)

Asparagus bean, Water
convolvulus (Section B3 and B4)

〇 Growth status and harvested
passion fruit on September 12th

Ditch A

Passion fruit and Basil (Section B1)

Ditch B

Harvested passion fruit （section B1）

Water convolvulus, Taro,Asparagus bean (section B3, B4)

〇 Growth status as of January 17,
2019 and harvested bok choy andsunny lettuce

Broccoli, strawberry(Section B1)

Ditch B

Ditch A

Garland chrysanthemum, Bok choy,
Sunny lettuce (section B2, B3)
Bok choy

Water dropwort, Snap pea(section B4)

Sunny lettuce

Sunny lettuce (section B3)

〇 Growth status of Flowers/Conifer (Ditch A)

24-May, 2018

9-July, 2018

12-September, 201817-January, 2019 ( view fromthe back side of the Ditch)

343 L/day

268 L/day

T-N Load

3.0Ditch B

238 L/day

20

2.5
2.0

15

1.5

10

1.050.500.0
AprilMayJune

July

AugustSeptember OctoberNovember December

January

February

MarchApril

30

3.0

T-N （mg/L）

25236 L/day

238 L/day

258 L/day

2.5

Ditch A

20

2.0

15

1.5

10

1.0

5

0.5

00.0
April

MayFigure 3.

June

July

AugustSeptember OctoberNovember December

January

February

March

April

Changes in nitrogen removal function of Ditch B and Ditch A(April 2018 to March 2019)

T-N Load （g/m2/day）

T-N （mg/L）

25

Outlet T-N

T-N Load （g/m2/day）

Inlet T-N

30

Table. 2 Nitrogen removal results of simple BGF Ditch (April 9, 2018 to March 18, 2019)
Ditch

survey period

Spring(9-April to22-May)
Early summer (5June to 10-July)
Summer (25-July to13-September)
Vegetables/Autumn (18Fruits
Septemberto 13(Ditch B)
November)
Winter (28November to 19February)
Early spring (6March to 18-MarchSpring(9-April to22-May)
Early summer (5June to 10-July)
Summer (25-July to13-September)
Flowers/Autumn (18Conifer
Septemberto 13(Ditch A)
November)
Winter (28November to 19February)
Early spring (6March to 18-March

Average T-N
Average T-N
Average nitrogen Removal
Average nitrogenconcentrationofconcentration
ofrate2load (g/m ･day) Inlet water (mg/L) Outlet water (mg/L) removal
ratio (%)
(g/m2・day)

0.73
0.99
2.35

9.9
11.6
22.0

6.0
6.1
9.6

0.28
0.47
1.31

38.4
47.5
55.7

0.66

8.9

3.2

0.42

63.6

0.58

7.9

5.4

0.19

32.8

0.69
0.71
0.95
1.63

9.1
9.9
11.6
22.0

5.3
6.6
6.5
12.10.29
0.24
0.42
0.73

42.0
33.8
44.2
44.8

0.65

8.9

5.5

0.24

36.9

0.58

7.9

6.6

0.10

17.2

0.68

9.1

6.8

0.17

25.0

Water sampling and analysis were conducted 2 to 3 times a month, 28 samples in total.

Table. 3 Average concentration and removal ratio of COD, SS, nitrogen,phosphorus, etc. in inlet and outlet water during the survey period

Items

Inlet water(Johkasou
effluent,mg/L)

CODMn
SS
T-N
NO3-N
T-P
PO4-P
KCa
Mg

10.2
0.5
11.7
10.3
4.8
4.8
13.9
12.3
6.3

Outlet water (mg/L)
Vegetables/
Flowers/
FruitsConifer(Ditch B)(Ditch A)
6.3 （38.2）
5.9 （42.2）
0.0 （100）
0.0 （100）
6.0 （48.7）
7.5 （35.9）
5.5 （46.6）
6.9 （33.0）
3.7 （22.9）
3.9 （18.8）
3.7 （22.9）
3.9 （18.8）
10.1 （27.3）
11.0 （10.6）
5.8 （7.9）

12.2 (12.2)
11.7 （4.9）
6.1 （3.2）⚫ Survey period: April 9, 2018 to March 18, 2019, average value of 28 samples in total⚫ () is the annual average removal ratio

5．Research Results in FY 2023
〇 Growth status and harvested sunnylettuce on June 5thTomato and Passion fruit(section A1)

Ditch A

forward

Ditch B

Calla and Manchurian wild rice(biotope pond)

backward

The grass is taller towards theforward of the ditch.
Corn (section A2 & A3)

Kidney bean and sunny lettuce(section B3)

Harvested sunny lettuce(234 g, section B3)

〇Growth status on July 25th and harvested
Molokheiya, Asparagus bean, and tomatoes

Tomato (section A1)

Ditch A

Ditch B

Molokheiya ：181 ｇ
Asparagus bean ：625 ｇ

Backward of Ditch A（Water convolvulus ）Backward of Ditch B(Asparagus bean)

Tomato （Ａ1：3150 ｇ, Ｂ1：580 g)

６. Safety consideration based on ISO guidelines
Table 4. Water quality of treated wastewater and crops that can be used as
irrigation water (ISO guidelines)
category(Quality of effluent)A(Very high quality)
B（High quality）
C（Good quality）
D(Medium quality)

BOD(mg/L)Ave.
Max.

SS（mg/L）
Ave.
Max.

fecal coliform bacteria(N/100mL)
95% ile.
Max.
≦10 or below the100detection limit

≦510

≦510

≦1020

≦1025≦200

1,000

processed food crops

≦2035

≦3050

≦1000

10,000non-food crops≦60100≦90140--available crops
vagetables consumed raw

industrial and seeded crops

Excerpt from ISO 16075-2, Table 1 (2020)

Table 5. Water quality classification of treated wastewater and number of barrier
points required for irrigation of each crop
Crop type
Vegetables consumed raw
Processing crops, pasture
fruit trees, garden crops
seeded crops, feed crops

A00
00

Excerpt from ISO 16075-2, Table 3 (2020)

Category of treated wastewater
BCD13
Prohibit to use02Prohibit to use
013001

Table 6. Barriers that help improve safety and their scores (example)
Type of barriers(1) Drip irrigation using a protective sheet to prevent irrigation waterfrom adhering to crops(2) Cleaning crops with potable water before sale(3) Irrigation cessation or interruption before harvest(4) Underground drip irrigation at a depth where irrigation water does
not rise to the ground surface due to capillary action

Number of barriers
11
1 to 2
3

Excerpt from ISO 16075-2, Table 2 (2020)In the BGF Ditch, pumice is filled to a height of 28 cm and the water level is maintained at
17 cm, so the effluent from the Johkasou (inlet water) does not rise to the surface of thepumice. For this reason, BGF Ditches are considered to correspond to the 3 points of thebarrier similar to underground drip irrigation in the ISO guidelines. Therefore, it issuggested that even vegetables produced in the BGF Ditch into which Category C treatedwastewater flows can be used for raw consumption.
At my house, an advanced treatment type Johkasou has been installed so that keeps theBDD and SS concentrations of effluent below than 10 mg/L (performance evaluationvalue). For this reason, it is thought that effluent with a quality close to Category B isbeing supplied to the simple BGF Ditch, which is presumed to bring safer.
In addition, in order to safely eat the vegetables and fruits we harvest, our family isreviewing our lifestyle, including refraining from using chemical substances that may havea negative impact on the environment.2) For this reason, food poisoning caused byharvested raw vegetables such as sunny lettuce, tomatoes, and strawberries has neveroccurred.

７．Summary
1.

By supplying Johkasou effluent to the simple BGF Ditch, it was able toproduce a wide variety of vegetables and fruits, including sunny lettuce,
tomatoes, Asparagus bean , passion fruit, and strawberries.

2.

The nitrogen removal rate from Ditch B (Vegetables/Fruits) during thesummer when biomass is actively growing was 1.31 g/m 2/day,approximately 1.8 times higher than that of Ditch A (flower/conifer).

3.

According to the ISO guidelines, it was suggested that raw vegetables andfruits such as sunny lettuce, tomatoes, and strawberries produced using
simple BGF Ditch can be safely consumed.

4.

This purification system is an energy‐saving and resource‐recycling
purification system for domestic wastewater that complies with the SDGs,
so we would like you to plant crops that suit the characteristics of eachregion and use it to conserve the water environment and resource
recycling.

5.

In order to safely eat harvested vegetables and fruits, it is important toreview our lifestyles, such as refraining from using chemical substancesthat may have a negative impact on the environment.

Acknowledgment

I received the cooperation of Ms. Akiko Nagaoka, Dr. Tsuyoshi
Ichinari, Dr. Masashi Goto, and many others from FujiClean Co.,Ltd for the installation of the Johkasou and water quality analysis.
I sincerely thank you for your long‐term cooperation.

References
1) Y. Ozaki: Japan Agricultural Research Quarterly, 33(4), 243–249 (1999)
2) Yasuo Ozaki: Journal of Johkasou, October 2019 issue, No. 522, 32-38
3) Yasuo Ozaki: Johkaasou Research, 32 (1), 1-8 (2022)
4) International Standard, ISO 16075-2(2020-11)

Thank you foryour attention ！
passion fruit

strawberryAnimals and plants that live in the biotope pond(August 24, 2017)
Potamogeton malaianus,
Myriophyllum spicatum

American bullfrog, blackspotted pond frog

Japanese killfish, Tadpole

Cybister japonicus

dragonfly larva

〇 Growth status and harvested corn on
July 9, 2023

Transplanted Asparagus bean
(section A2 & A3)

Ditch A

Ditch B
Transplanted Corn (section B3)

Ditch A (Tomato, Passion
fruit, etc.)Ditch B (Tomato, Passion
fruit, etc.)

Corn (A2: 1,500 g, A3: 1,170 g)

Growth status of tomatoes, passion fruits, etc. (7/17)
Examples of vegetables and fruits harvested using a simple
BGF Ditch (FY 2021, Tsukuba City, Ibaraki Prefecture)

Growth status of sunny lettuce, kidneybeans, etc. (May 28)

Snap peas （7-April）

Strawberry （23-April)

Leaf lettuce (18-May）

Garlandchrysanthemum(18-May）

Sunny lettuce (20-May)

Kidney bean (19-June)

Tomato and Asparagus
bean (24-July)

Passion fruit(18-August）