Glycative Stress Research
Online edition : ISSN 2188-3610
Print edition : ISSN 2188-3602
Received : December 6, 2020
Accepted : February 13, 2021
Published online : March 31, 2021
doi:10.24659/gsr.8.1_20

Original Paper

Water quality improvement effect from the installation of special-glaze-applied
ceramics: Benten Pond, Ichikawa, Chiba, Japan
Yoshikazu Yonei 1), Kyle Haasbroek 1), Masayuki Yagi 1), Shinichi Sugiura 2),
Department of Parks and Green Spaces, Ichikawa City 3)1) Anti-Aging Medical Research Center and Glycative Stress Research Center, Faculty of Life and Medical Sciences,
Doshisha University, Kyoto, Japan
2) Faculty of Pharmaceutical Sciences, Doshisha Women's College of Liberal Arts, Kyoto, Japan
3) Department of Parks and Green Spaces, Ichikawa City, Chiba, Japan

Abstract

Objective : The special-glaze-applied ceramic pieces used in this study are bisque fired ceramics manufactured by applying
a special glaze. It has been suggested that cyanobacteria, which are oxygen-producing photosynthetic bacteria, may proliferate
when ceramic pieces are placed in soil or water. In this study, we installed ceramic pieces in the Benten Pond (Ichikawa,
Chiba, Japan) and verified the effect of the pieces on water quality.
Method : Benten Pond is a closed water system with a little flow from upstream where a water inlet pipe is located, todownstream where a drainage channel is located. We placed three sandbags filled with approximately 6 kg of ceramic pieces
in the water. We observed reddish mud and oil film around the water inlet pipe that were determined to be iron oxide biomats
produced by iron bacteria, and ceramic pieces of 1 kg were scattered only on the west side of the pipe.
Result : The values of Biochemical Oxygen Demand (BOD)/Chemical Oxygen Demand (COD), which are indicatorsof water quality, were 1.8 /4.2 mg/L when the ceramic pieces were placed (November 21, 2019), the values temporarily
increased during summer and decreased to 1.2/3.5 mg/L after one year. An improvement was observed in suspended
solids, which dropped from 17 mg/L to 12 mg/L. The previous value of total nitrogen was 14 mg/L, which was well above
the standard value. Total nitrogen decreased during the summer and then approached the previous value. Although total
phosphorus increased temporarily during summer from the previous value of 0.034 mg/L, the value was 0.030 mg/L after one
year. The iron oxide biomats almost disappeared in the area where the ceramic pieces were placed, and the biomats remained
unchanged in the area where the pieces were not placed. Adverse events associated with the installation of ceramic pieces
were not observed.
Conclusion : The installation of ceramic pieces improved the water quality and reduced iron oxide biomats. Further
studies regarding the involvement of cyanobacteria are required.

KEY WORDS: Special ceramic pieces, water quality improvement, cyanobacteria, iron oxide biomats, iron bacteria

Introduction

The special-glaze-applied ceramic pieces (referred to as"ceramic pieces") introduced in this paper were developedin 2000 by Shuichi Sugita ( Noah Co., Ltd., Oita, Japan).
Water treated with the ceramic pieces has been confirmed
to have odor reduction and bactericidal effects 1). Although
the mechanism for the effects was unknown, studies haveContact Address: Professor Yoshikazu Yonei, MD, PhD
Anti-Aging Medical Research Center,
Graduate School of Life and Medical Sciences, Doshisha University
1- 3 Tatara Miyakodani, Kyotanabe, Kyoto, 610- 0394 Japan
TEL & FAX: +81-774-65-6394 e-mail: yyonei@mail.doshisha.ac. jp
Co-authors: Haasbroek K, cygd2001@mail.doshisha.ac.jp;
Yagi M, myagi@mail.doshisha.ac.jp; Sugiura S, ssugiura@dwc.doshisha.ac.jp;
Department of Parks and Green Space., koenryokuchi@city.ichikawa.lg.jp_ 20 _

suggested that this could be due to the proliferation of
cyanobacteria. Cyanobacteria are oxygen-producing
photosynthetic bacteria and have existed for morethan 2 billion years on Earth. A simple explanation for
the improvement effects is that the dissolved oxygen
concentration increases due to the oxygen produced.
The resulting oxidation accounts for the odor reduction,

Glycative Stress Research 2021; 8 (1) : 20-28(c) Society for Glycative Stress ResearchGlycative Stress Researchbactericidal action and water purification effects. Studies
to clarify the mechanism responsible for the special effects
produced in the ceramic treated water will become more
important. In this study, we placed ceramic pieces in Benten
Pond (Ichikawa, Chiba, Japan) and verified the effect of thepieces on water quality.

MethodMaterials and Methods
The ceramic pieces are bisque fired ceramics
manufactured by the application of a special glaze. The
glaze does not contain any harmful chemicals or chemical
products. It is manufactured by mixing multiple plant
embryo buds and sprouts found in Japan and fermented using
special enzymes over a long period of time. The speciallyprocessed glaze (containing iron oxide) is then applied tothe surface of the ceramic pieces (spherical and ellipsoid
fine particles), the pieces are dried and subject to heattreatment at a high temperature (1,300 °C for 1 hour) 1). The
ceramic pieces are spherical in shape, approximately 2.5 cm
in diameter and weigh about 15 g each.
Three sandbags (48 cm x 62 cm, manufactured frompolyethylene) filled with approximately 6 kg of ceramicpieces were prepared. The ceramic pieces were purchasedfrom Noah Co., Ltd. The pieces were installed in Benten
Pond located at Benten Pond Park, Ichikawa, Chiba, Japan.
Figure 1 shows the installation locations (three places). The
area around Benten Pond is now a residential locality. There
are no agricultural fields in the neighboring area. One water
inlet pipe is present on the north side of the pond, whicha)receives rainwater after rainfall, but the flow rate during clear
weather is low and is less than 4 L/min. A part of the water
inlet pipe goes through the soil. There is no contamination
by domestic wastewater. There is an outflow channel to thesouth, and the flow rate here is also low.
Reddish mud and a filmy substance were observed on
the water surface in the area around the water inlet pipe,
which were determined to be iron oxide microbial mats(biomat) 2, 3). This is also known as "red water", "red sludge"
or "red mud". However, "red mud" can sometimes refer toindustrial waste, which should be differentiated.
The industrial waste "red mud" is produced whenbauxite is refined into alumina (aluminum oxide) with theBayer process 4, 5). In this process, bauxite is crushed anddissolved in sodium hydroxide to obtain sodium aluminate
solution, from which aluminum hydroxide is precipitated,
and aluminum is recovered. The dissolved residue is thesludge that is discharged during the process. This red mud
contains mostly of the impurities in bauxite, and the redcolor originates from the primary component, hydrated ironoxide Fe (III). The primary component is iron oxide Fe (III)(Fe 2 O 3) at about 40 %, the next highest are aluminum oxide(Al 2 O 3) and silicon dioxide (SiO 2) at about 10%, and othercomponents include calcium oxide (CaO), titanium dioxide(TiO 2) and sodium oxide (Na 2 O). The dumping of red mud
into the ocean is a reality in Japan, with environmental
consequences. Initiatives are being implemented to reduce
the amount of waste dumped into the ocean.
Ceramic pieces (about 1 kg) were scattered on the soil
(over an area of about 2 m in diameter) to the right (west) of
the water inlet pipe to verify the effect of ceramic pieces on
the iron oxide biomats. The water depth in this area ranged
from 0 to 5 cm, and most of the ceramic pieces were almost

b)

A

A B

↓ 流入管
↓ 流入管

B
C

C

A A

B B

C C

★ ★

1. Aerial Photo of Benten Pond.
Fig.Fig.
1 Fig.
1a) a)b) b)

a) Panoramic view. b) Magnified image Ceramic pieces are placed at locations A, B and C in the water. Sandbags (approximately

6 kg) are filled with ceramic pieces. About 1 kg of ceramic pieces were spread inside the red circle (an area of around 1 m indiameter). Water quality measurement site. Source: Google Aerial Photograph.

_ 21 _

Water Quality Improvement Effect from Special-glaze-applied Ceramics

completely submerged. Also, a clay-like material (about 10kg) made by pulverizing the ceramic pieces was spread on
the periphery.

Water Quality Survey
A water quality survey was conducted at a fixed location
every three months. The items measured were hydrogen ion
concentration, temperature, biochemical oxygen demand(BOD), chemical oxygen demand (COD), suspended solids(SS), total nitrogen and total phosphorus. The water quality
was tested by Chugai Technos Corporation (Hiroshima,
Japan). The location for the measurement is shown in Fig. 1.
The measurement location is located near the outflow
channel on the south side of Benten Pond.

Results

Changes in Appearance
The appearance of the water in Benten Pond is mostlytransparent and odorless, and the pond is inhabited by carp,
crucian carp, and Japanese pond turtles, with ducks and othermigratory birds flying in and various insects living aroundthe pond. One water inlet pipe is located to the north of thepond, and some of the rainwater after rainfall causes thewater inflow volume to increase, but the average volume ofwater flowing into the pond is less than 5 L/min. The soil(radius of about 2 m) around the water inlet pipe (depth ofwater about 0 to 5 cm) had a reddish tinge, and an oil-likefilm was present in some areas of the water surface. These
areas were also odorless. The films are iron oxide biomats
formed from the proliferation of iron bacteria.
The appearance three months after the installation
was the same as when the ceramic pieces were installed, areddish tinge was observed in the soil, and a reddish film hadformed on the water surface ( Fig. 2 ).
The situation one year after installation is shown in
Fig. 3. A difference in the color tone of the soil and water
surfaces in the left and right sides of the water inlet pipe wasobserved. The area on the left (east) was unchanged from 1
year ago: it had iron oxide biomats and a reddish tinge in thesoil and film formation on the water surface was observed.
On the other hand, the soil on the right (west) of the water
inlet pipe where the ceramic pieces were placed was darkbrown, and film formation on the water surface could not be
observed. The iron oxide biomats had disappeared.
Offensive odor, abnormality or death of native organisms,
pest outbreaks, red tide or blue-green algal blooms were notobserved during the installation period.

Fig. 2. Iron oxide biomat in the periphery of the inlet pipe
(after three months).

The soil in the periphery of the inlet pipe has a reddish tinge, andfilm-like structures are observed on the water surface. There is no
significant difference in soil color on the left and right sides of thedrainage pipe. Rainwater flows into the inlet pipe, and the inflow
is temporary after rainfall. The left side of the pipe is untreated.
Ceramic pieces are placed on the right side. The condition has
not changed three months after the placement of ceramic pieces.
Photographed on February 21, 2020.

Fig. 2

a)

b)

Fig.
Fig.
a)a) oxide biomat in the periphery of the inletb)b) pipe (after one year).
Fig.
3.33Irona) In the periphery of the inlet pipe, the soil on the left side was reddish, while the soil on the right, where theceramic pieces were spread, was dark brown. b) On the left side of the pipe, reddish mud and oil film-likestructures are observed, unchanged from a year ago. Photographed on November 20, 2021.

_ 22 _Glycative Stress Research

Changes in Water Quality
Results of the water quality measurements are given in
Table 1. The temperature of the samples was kept constant(25 ~ 26°C ) when conducting the water quality tests.
Hydrogen-ion concentration was almost constant (pH 7.2),
except for June when pH was 7. 5.
Water quality at the start of the study was COD
standard B (5.0 mg/L or less), which corresponds to Fishery
Class 3 (for aquatic products such as carp and crucian carp
inhabiting eutrophic lake-type waters), Industrial Water
Class 1 (regular purification operation such as sedimentationis performed) and Agricultural Water, and the SS standard
was C (15.0 mg/L or more), which corresponds to Industrial
Water Class 2 (advanced water purification is performed byinjecting chemicals or special water purification operations).
The standard for total phosphorus was IV (0.05 ml/L orless), which corresponds to Fishery Class 2, while the valueof total nitrogen was outside the standard (1 mg/L or more).
SOD was 1.8 mg/L when the ceramic pieces wereplaced (November 21) and increased on May 12 (2.0 mg/L)
and August 17 (3.1 mg/L) when the temperature increased
but was 1.2 mg/L one year later (November 20). Overall,
SOD had improved from the previous year.
COD was 1.8 mg/L when the ceramic pieces wereplaced and increased on May 12 (4.5 mg/L) and August 17( 7.5 mg/L) when the temperature increased but was 3. 5 mg/L
one year later (November 20). Overall, COD had improved
from the previous year.
SS improved to 12 mg/L after one year compared to 17
mg/L when the ceramic pieces were placed. The previous
value of total nitrogen was 14 mg/L, which was significantly
above the standard value. Total nitrogen decreased during
summer and then approached the previous value. There wereno findings of worsening conditions.
Total phosphorus was 0.034 mg/L when the ceramicpieces were placed and increased temporarily only on August
17 (0.057 mg/L), and the value was 0.030 mg/L after one
year.
One year after the special ceramic pieces had been
installed, COD standard was B (5.0 mg/L or less), whichcorresponds to Fishery Class 3, Industrial Water Class 1 andAgricultural Water, and SS standard was C (15 mg/L or more),
which corresponds to Industrial Water Class 2, and there wasno change in the category. The standard for total phosphorus
improved to category III (0.03 ml/L or less) corresponding to
Water Supply Class 3 (Water treated by advanced cleaning
operations including pretreatment ("special type" meanswater treatment by special cleaning operation that canremove substances with a smell.)). The value of total
nitrogen was outside the standard (1 mg/L or more) andremained unchanged.

Discussion
We installed ceramic pieces for this study in Benten
Pond, a closed water system, and changes in water quality
were examined over a year. The pond is small in size, andspecific environmental water quality standards have notbeen established. Compared with the environmental quality
standards for lakes (reservoir capacity of 10 million m 3 ormore), the water quality of Benten Pond was characterized
by the total nitrogen amount, which significantly exceeding
the standard value. An improvement in BOD and COD was
observed one year after the special ceramic pieces had been
installed. The iron oxide biomats formed due to the ironbacteria found in the periphery of the inlet pipe were almost
completely eliminated in the area where the ceramic pieces
were installed.
The COD standard at the start was B (5.0 mg/L or less),which corresponds to Fishery Class 3, Industrial Water Class 1
and Agricultural Water, and the SS standard was C (15.0
mg/L or more), which corresponds to Industrial Water Class
2. The standard for total phosphorus was IV (0.05 mg/Lor less), which corresponds to Fishery Class 2. The value of
total nitrogen was outside the standard (1 mg/L or more).
One year after the ceramic pieces had been placed,
COD standard was B (5.0 mg/L or less), which corresponds
to Fishery Class 3, Industrial Water Class 1 and Agricultural
Water, and SS standard was C (15 mg/L or more), whichcorresponds to Industrial Water Class 2, and there was nochange in the category. The standard for total phosphorus

Table 1. Results of water quality test.
Date(Time course)pH

Measurement
limit

Temperature

Nov 21, 2019(0)

Feb 21, 2020
( 3 months)

May 12, 2020 Aug 17, 2020 Nov 20, 2020
(6 months)(9 months)(1 year)

7. 2

7.2

7. 5

7. 2

7.2

℃

25

26

25

25

26

Unit

Biochemical oxygen
demand (BOD)

0.5

mg/L

1.8

0.6

2.0

3.1

1. 2

Chemical oxygen
demand (COD)

0.5

mg/L

4. 2

2.0

4. 5

7.5

3. 5

Suspended solids (SS)

1

mg/L

17

4

10

10

12

0.05

mg/L

14

14

12

11

13

0.003

mg/L

0. 0340.013

0.0 28

0.057

0.030

Total nitrogen
Total phosphorus_ 23 _

Water Quality Improvement Effect from Special-glaze-applied Ceramics

improved to category III (0.03 ml/L or less) corresponding to
Water Supply Class 3. The value of total nitrogen was outside
the standard (1 mg/L or more) and remained unchanged.
From the results obtained, it was determined that theplacement of ceramic pieces improved the water quality of
Benten Pond.

Inferred Action Mechanism of
the Special Ceramic Pieces
Cyanobacteria breeding on the surface are presumed
to play an important role in the action mechanism of theceramic pieces 1). Cyanobacteria can produce oxygen throughfixation of nitrogen and carbon, which are present in waterand soil, using the reaction of photo-amplifying enzymes.
This reaction is significantly different from photosynthesisin common plants that use CO 2 and chlorophyll, andcyanobacteria can produce oxygen even under no-light or
low light environments 6). The nitrogen that is taken up has
cyanophycin granules, which are non-ribosomal peptides
made of arginine and aspartic acid, and is used as a nitrogen
reserve 7). Part of it is used as aminolevulinic acid (ALA) 8).
ALA is a basic substance that is essential for developing manylife forms and is found in mitochondria and chloroplasts. It isa source of hemoglobin in animals and chlorophyll in plants.
While the mechanisms of cyanobacteria proliferation
caused by the special ceramics are still under investigation,
the release of trace elements may play a role. Certain traceelements, while toxic in high concentrations, are neverthelessnecessary for metabolism. Safe amounts of metals containedin the special ceramics may be available for utilization bycyanobacteria and assist in their proliferation. Cyanobacteria
require of a variety of metals as cofactors for electrontransfer and other uses 9, 10) : metals utilized by cyanobacteria
include iron, zinc, nickel, copper, cobalt, manganese andmolybdenum. While they are present in small amounts, thespecial ceramics contain Fe 2 O 3, ZnO, CuO and MnO in
addition to their primary components 1).
BOD and COD values in Benten Pond improved, andthe contribution of oxygen produced by cyanobacteria isconsidered to be the reason. The qualitative improvements inwater quality and soil and the decrease in SS are presumed
to be a result of these actions. Oxygen in water acts as abactericidal agent against anaerobic bacteria and promotes
the growth of aerobic bacteria. As a result, the ceramicpieces are presumed to have contributed to improving thewater quality environment.

Potential of Cyanobacteria
Cyanobacteria breed extensively in the oceans, fresh
water and soil. The taxonomy and scientific names of
cyanobacteria have not been yet been definitively organized.
Two genera of cyanobacteria, Synechocystis 11, 12) andCyanothece 13), are major targets for study and contain
important model species. Cyanobacteria is the only taxon ofbacteria that performs oxygen-producing photosynthesis.
They are prokaryotic organisms that do not have a nucleus
enclosing the DNA inside the cells and are categorized as
eubacteria. Cyanobacteria are also said to be the ancestor ofchloroplasts that are present in higher plants. They can adapt
to environments requiring salt tolerance 14) or a wide diurnal

variation 15), and convert atmospheric CO 2 into sugar andcellulose.
The mechanisms of oxygen-producing photosynthesis
in cyanobacteria are extremely diverse. Cyanobacteria use
several types of chlorophyll and rhodopsin for various
purposes and have shown a high degree of adaptability tobreed even in harsh natural environments. As a result of
their photosynthetic metabolism, they require more metals
compared to other bacteria 16) and produce high amounts ofreactive oxygen species, necessitating strong DNA repair
mechanisms 17). Although there are many unansweredquestions about cyanobacteria, they have a unique hidden
potential. In the environmental field, oxygen photosynthetic
bacteria have been used for manure treatment and anti-odor
measures at pig farms and wastewater treatment at foodprocessing plants 18). ALA is synthesized in the cyanobacteria
cells. It is reported that the use of photosynthetic bacteria asa fertilizer in agriculture increased the yield and improved
quality 19). On the other hand, some species of cyanobacteria
can cause red tide and blue-green algal blooms 20, 21). There
have been no cases of red tide or blue-green algal blooms inareas where ceramic pieces have been used.

Water Quality of Benten Pond
The total nitrogen concentration in water is set as animportant factor for the conservation of the living
environment. An environmental standard of 0.1 to 1.0 mg/L
has been established for lakes and seas by type. The water
quality of Benten Pond was characterized by a high total
nitrogen concentration. There are no farmlands, orchards
or pig farms around the pond at present. The area has
an established sewage system and mixing of domestic
wastewater is unlikely. A pear orchard was once present inthis area, and the soil may still be affected by fertilizers
used in the past. The possibility of nitrogen present in thesoil having permeated underground and flowed into thepond cannot be denied.
Total nitrogen includes nitrate-nitrogen, nitrite-nitrogen,ammonia nitrogen and organic nitrogen. Daily life andagricultural activities often cause nitrate and nitrite nitrogencontamination. Untreated domestic wastewater can cause
organic contamination and eutrophication. The degree ofcontamination varies depending on the treatment method
used for domestic sewage, farming style, soil environment
and weather conditions in the area. The area around Benten
Pond is a residential locality, and there are no farmlands
around the pond at present. Ammonia nitrogen is derived
from ammonia formed by the hydrolysis of proteinsdischarged from kitchens and urea discharged from domestic
wastewater. Judging from the residential environment around
Benten Pond, with an established sewage system, a large
amount of ammonia nitrogen is unlikely to be produced norenter the pondwater. Although microorganisms decompose
the nitrogen compounds, they also consume oxygen andcause BOD to increase.
Next, we will compare the water quality of Kasumigaura(Ibaraki, Japan) and Benten Pond. Kasumigaura (area 220.0
km 2) is the second largest lake in Japan after Lake Biwa
(Shiga, Japan), and information on its water quality isreadily available 22). Since the 1970s, the Ministry of Land,
Infrastructure, Transport and Tourism has been implementing_ 24 _Glycative Stress Researchwater purification measures to counter large outbreaks ofblue-green algae, offensive smells, and mass mortality offreshwater clams and cultivated carp, mainly in summer.
The COD (average of all water bodies) value in
Kasumigaura reached a record high of 11.0 mg/L in 1979
but has decreased since 2010, reaching 6.9 mg/L in 2019.
Since organic matter is produced by phytoplankton throughphotosynthesis in lakes, COD is higher than the inflowing
rivers. Seasonal variation has also been observed, with
COD increasing in summer and decreasing in winter. The
variation is associated with the growth of phytoplankton.
Total nitrogen varies depending on the inflowing river.
A higher value ( > 6.0 mg/L) is observed in the inflow of theKitaura river compared to the inflow of the Nishiura river(2.7 to 3.1 mg/L, Fig. 4 ). The reason is considered to be thenitrogen content of fertilizers (compost) used in farmlands
flowing into the rivers through groundwater over time. The
reason for a lower total nitrogen concentration in the lake (1.1
mg/L in 2019) than in the inflowing rivers is because when
nitrate ions, one of the components of nitrogen present inriver water, enters the lake, they are converted into gaseous
nitrogen by the action of denitrifying bacteria and released
into the atmosphere (denitrification). Although nitrogen at thelake center shows little seasonal variation, a decrease in thesummer and an increase in the winter are observed in somewater bodies. The reason is that dissolved nitrogen increases
when the water temperature is low.
The total phosphorus concentration indicates an upward
trend until 2008, but has declined to 0.094 mg/L in 2019.
In recent years, phosphorus concentration in the lake tends
to be higher than that of the inflowing rivers. The reason
is believed to be due to the seepage (elution) of phosphorus
from the mud (bottom mud) that accumulates at the lake's
bottom. Seasonal variation of total phosphorus indicates thatit tends to increase in summer and decrease in winter. The
elution of phosphorus from the bottom mud is believed tooccur when the dissolved oxygen concentration at the lake's

bottom is low (becomes anaerobic).
Benten Pond has lower COD, BOD, SS, and total
phosphorus than Kasumigaura. It can be determined thatthe "water quality is not poor" for the pond except for total
nitrogen. The seasonal variation of COD, total nitrogenand total phosphorus in Benten Pond is similar to that of
Kasumigaura.

Iron Oxide Biomats
Iron bacteria are involved in the production of ironoxide biomats. Iron bacteria are widely present in soil andthrive in springs and soils that contain high levels of divalentiron (Fe (II)), as they use energy from the oxidation ofwater-soluble divalent iron ions ( Fe 2 + ). Iron bacteria oxidize
Fe (II) dissolved in water to form trivalent iron ( Fe (III)) asa water-insoluble hydroxide or oxide, which is deposited andcollected inside and outside the bacterial cells. A film ofiron oxide is formed from Fe (III), and when the bacteria die,reddish-brown sediment is created and a biomat (microbialfilm) is deposited. The iron oxide film resembles an oil film
in areas where there is no flow of water 23 -25). Iron bacteria
include genera Leptothrix 26, 27) and Gallionella 28, 29).
Iron oxide biomats have also been observed near water
inlets of paddy fields and leakage sites in concrete structures.
Although the appearance of the landscape is spoiled, bothbacteria and sediment are harmless at levels existing in nature.
Treatments such as aeration and coagulative sedimentation
are implemented to improve the visual appeal of thelandscape 30). Since these are methods used to remove
dissolved iron by turning it into a solid as iron oxide, thesolid must be regularly removed and disposed of as waste.
Therefore, these are not simple methods that are suitable foruse in springs, ponds, swamps and rivers.
In a typical river, most dissolved iron forms complexes
with humic substances (HS) and flows downstream 31). In
addition to HS, other organic ligands that form complexes

8.0

Total nitrogen (mg/L)

7.0
6.0

Kitaura inflow
Nishiura inflow
KitauraNishiura

5.0
4.0
3.0
2.0
1.0
0.0

S47 S49 S51 S53 S55 S57 S59 S61 S63 H2

H4H6

H8 H10 H12 H14 H16 H18 H20 H22 H24 H26

Time course (year)

Fig. 4. Water quality in Kasumigaura (Ibaraki Prefecture): Total nitrogen.

Total nitrogen concentration in the Kitaura inflow river is exceptionally high compared to the lake water. Cited
from reference 10).

_ 25 _

Water Quality Improvement Effect from Special-glaze-applied Ceramics

with Fe (II) and Fe (III) in the water environment include
siderophores 32, 33) produced by microorganisms such asbacteria and eumycetes, and exopolymeric substances (EPS)such as polysaccharides produced by bacteria and algae 34, 35).
Since soluble Fe (III ) complexes are created if thesesubstances are abundant, iron oxide biomats are less likely
to form.
What is the effect of cyanobacteria proliferation,
which performs oxygen-producing photosynthesis, in anenvironment with iron oxide biomats?
Iron oxidizing bacteria adapted to neutral pH
are microaerophilic chemotrophs. A small minimum
concentration of oxygen is necessary for oxidizing Fe (II)into Fe (III). However, under aerobic conditions at a neutral
pH, abiotic oxidation of iron occurs spontaneously andoutcompetes bacterial iron oxidation, which is a relatively
slow process. Thus, a mostly deoxygenated environmentis required for iron oxidizing bacteria to proliferate 36). In
natural environments they tend to exist at the boundary
between aerobic and anaerobic environments 37). As Benten
Pond maintains a neutral pH while iron bacteria are able
to proliferate, the oxygen concentration is likely low.
When the amount of dissolved oxygen is high, Fe(II) quickly oxidizes to Fe (III), and Fe (II) utilization byiron bacteria is expected to reduce. As a result, the growthof iron bacteria is similarly reduced. Many cyanobacteria
are reported to take in inorganic dissolved iron Fe 2+ andFe 3 + from water into the cells through transport proteinsin the cell membrane 38). Iron is vital to cyanobacteria
metabolism, and plays an important role in the processes ofphotosynthesis and nitrogen fixation 39, 40). The presence of
cyanobacteria will provide additional competition for ironas well as increase oxygenation, further suppressing ironbacteria. In a study of freshwater Lake Taihu in China 41),
areas of the lake that were dominated by cyanobacteria hadsignificantly lower abundance of iron bacteria compared
to typical environments. Dissolved iron was also decreasedin these areas compared to parts of the lake dominated byaquatic plants. Under aerobic conditions, in the presenceof a large quantity of dissolved oxygen, bacteria and algae
increase, as do corrosive substances and soluble complexes.
It also affects iron oxide Fe (III), which is alreadysedimented. Some of the iron oxides deposited at the bottomof the water body by coagulation and sedimentation are
reduced to Fe (II) in the anaerobic reduction layer and eluted
as Fe 2 + ions 42, 43). Fe 2+ released from the deposit directly
into the water is oxidized relatively quickly, but it forms
complexes such as organic complex Fe (III) on encounteringorganic macromolecule polymers (such as humic acid andsiderophore) and dissolves. The iron supplied directly fromthe bottom of the water body and dissolved as organic
complex iron forms an iron circulation system in water. Theseiron types are considered to be widely used by organisms
other than iron bacteria. Microorganisms particularly tend touse the siderophore complex Fe (III).

Safetydate. The safety of the material is sufficiently guaranteed.
Since the amount of each element produced by ceramictreatment is maintained at the optimum mixing ratio, ceramictreatment is assumed to have various beneficial effects
such as increased physiological activity. No adverse eventswere observed, such as abnormal changes in the vegetation
around the pond, an increase in the number of dead aquaticorganisms, or the breeding of pests.

Study Limitations
There was a high concentration of total nitrogenin Benten Pond. However, since only total nitrogen wasmeasured in this study, it was impossible to determine
whether nitrate-nitrogen, nitrite-nitrogen or ammonia
nitrogen was the cause. Since water from the pond was nottested for microbial composition, the presence and extent of
cyanobacteria proliferation could not be verified.

Conclusion
Verification results of water quality improvement effectwith the installation of ceramic pieces in Benten pond,
Ichikawa, Chiba, showed an improvement in BOD, COD
and a reduction in iron oxide biomat formation due to ironbacteria after one year, and no adverse events were observed.
Although the underlying mechanism is unknown, it is inferredthat the ceramic pieces have the effect of promoting theproliferation of oxygen-producing photosynthetic bacteria,
and the phenomenon is awaiting further study.

Financial disclosure
The authors declare they have nothing to disclose
regarding funding or conflicts of interest with respect to thismanuscript.

Acknowledgements
This study was supported by Department of Parks
and Green Spaces, Ichikawa City and by the “ Researchand Development Platform for the cultivation of functional
agricultural products and the circular agriculture whichaims for water quality improvement in the increased content
of anti-glycation substances ( http://www.yonei-labo.com/
pdf/ liaison_doc.pdf )” of “ Field for knowledge Integration
and Innovation, ” which is performed by The Ministry ofAgriculture, Forestry and Fisheries Platform (https://www.
knowledge.maff.go.jp/platform.html). The authors are
greatly indebted to Mr. Tsutomu Kaizu, Ichikawa City
council member, and Ms. Masako Kiyama, Secretary.

The amount of trace elements in ceramic and ceramictreated water is below the toxicity threshold level and is nontoxic. The ceramic pieces have been used for more than 25
years, and no side effects or hazards have been observed to_ 26 _Glycative Stress Research

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