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学生の研究活動報告−国内学会大会・国際会議参加記 25

Applicability of sewage heat
for improvement of nitrification
performance of a trickling filter

tics, Japan). The bottom end of the pipe was covered
with a plastic net with a 5-mm mesh, that held up thefilter media. As a sewage heat utilization system, a coiltube made of polytetrafluoroethylene with 4-mm in di-神田崚Ryo KANDA
環境ソリューション工学専攻修士課程

2年

ameter and 6.0-m in length was installed into the reactor A alone. The influent sewage flowed into the denitrification tank via the coil tube. The coil tube was notinstalled into the reactor B because the reactor B was a

1. Prefacecontrol. The exterior of both reactors was covered withI presented a poster entitled above at IWA Worldan insulation (Pipe Cover, Toray Pef Products, Japan).

Water Congress & Exhibition 2016 in Brisbane,

The denitrification tank consisted of an acrylic tank

Queensland, Australia from 9th to 13th October 2016.

with 125-mm in height, 70-mm in width and 320-mm
in depth and was filled with string-shaped and brush-

2. Summary and Presentation

like contact media (KC-30, Dainippon Plastics, Japan).

2.1 Introduction

Total length of the media was 1.8 m. Wastewater

The modified Ludzack-Ettinger process requires aflowed tortuously through the contact media. The effec-

high-energy input to operate blowers for aeration in ative volume of the tank was 2.15 L. Wastewater

nitrification tank. To solve this drawback we developed

pumped up from a sewage chamber in Ryukoku Uni-a new biological nitrification-denitrification process

versity, Japan was used for all the experiments. The op-with a trickling filter for nitrification and an anaerobic

erational conditions were shown in Table 1. In addition,biological filter for denitrification. However, low tem-to simulate actual sewage, the sedimentation tank wasperatures less than 15℃ critically affect the bioactivity

heated to around 20℃ with a ribbon heater (JH-128,of nitrifying bacteria, which play an important role inMisec, Nagoya). Consequently, the temperature of ef-oxidizing ammonia and nitrite. Accordingly, complete

fluent from sedimentation tank was fluctuated between

nitrification using a conventional trickling filter is difficult in winter. To prevent the inactivation of those bacteria, we focus on sewage heat. Sewage is warmer than
the air in winter. In this study, we discussed an availability of sewage heat for warming the trickling filter inwinter.
2.2 Material and Methods
Figure 1 illustrates the experimental set up. A pair ofreactors (reactor A and B) with the same configuration
was prepared for comparison. The trickling filter for nitrification consisted of an acrylic pipe with 80-mm indiameter and 1000-mm in height and 540-g of tubular
filter media made of polyethylene with 15-mm in diameter and 15-mm in length (LT-15, Dainippon Plas― S-75 ―Fig. 1

Experimental setup (reactor A)

Table 1Term

Operational conditions

HydraulicAir
Flow rate Circulation
loading temperature（L d−1） rate（％） 3 −2 −1（m m d ） （℃）

Ⅰ1 Oct.-26 Nov.

8.0

250

5.57

15.0-25.3

Ⅱ27 Nov.-25 Jan.

8.0

250

5.57

4.6-14.920.5±1.9℃ for all the experiments.
2.3 Results and Discussion
Figure 2 summarizes the changes in NH4-N, NO3-N,NO2-N, and dissolved organic nitrogen concentrations
over time. The averages of DN removal efficiency interm I (≥15℃) and term Ⅱ (＜15℃) were 65.9±17.3% and 71.2±11.6% for the reactor A, and 57.5±22.2% and 51.8±15.1% for the reactor B. Although there
was no significant difference in nitrogenous water
qualities in the effluent between two reactors in term I,
a significant difference (p＜0.05) was detected by the tFig. 2

test in term Ⅱ. The nitrification efficiency of the reac-Changes in DN components over time

tor A was tended to increase from 51.2±27.3% in term
I to 62.5±17.9% in term II in spite of air temperaturedrop to lower than 15℃ in term II, whereas that of thereactor B was tended to decrease from 39.2±25.6% interm I to 20.7±9.2% in term II. Accordingly, a further
improvement of heating system will be required for nitrification in such a severely cold season. Figure 3
shows the relationship between the flow rate of
temperature-regulated tap water and the temperature
difference in the filter bed between reactor A and B. As
the sewage heat utilization experiment was performedat the sewage influent flow rate of 8 L d−1, it was inferred that the temperature in the filter bed of reactor A
was maintained 1.3±0.2℃ higher than that of reactor
B and 2.5±0.6℃ higher than the air temperature. Con-Fig. 3 Relationship between the flow rate of tap
water regulated at 20°
C and the temperature difference in the filter bed between reactor A and B.
The error bar shows sample standard deviation.

3. Acknowledgement

sequently, the utilization of sewage heat for warming

We wish to express our appreciation to Prof. N.

the trickling filter was effective in enhancing the nitrifi-Kishimoto for his steadfast support and encouragement.

cation performance in winter.

It was excellent experience for me to share my researchworks with many international researchers.
― S-76 ―