Biofilm characterization and operation performance in a

single stage partial nitritation/anammox process with a function carrier

1Graduate School of Environmental Studies, Tohoku University, Miyagi 980 -8579, Japan.2Department of Civil and Environmental Engineering, Tohoku University, Miyagi 980 -8579, Japan

Yunzhi QIAN1, Yan GUO2, Junhao SHEN1 & Yu-You LI1,2*

The 8 th International Symposium on Water Environment Systems----- with Perspective of Global Safety (Nov. 13th ~ 14 th , 2020)

1. Introduction1.3 Objectives

Problem: Sludge washout and coexistence of AOB and anammox bacteria

Proposal: Adding carrier Double biofilm structure

High amount of biomass ＆ Avoid sludge washout

SPNA reactor Carrier

The objectives of this study are to:

1.2 Problem and proposal 1.3 Objectives

study the formation characterization of biofilms;

determine the high activity maintenance strategy of

biofilm under long-term operation.

The outcomes of this study promise to include valuable

insight into SPNA process operation, and serve to the

further expansion of SPNA process application in industrial

applications

2. Material & Methods

Figure 1 Photo of carriers.

Table 1 Characteristics of carrier

2.1. Carrier 2.2. Apparatus

Figure 2 Schematic diagram of ALR-SPNA: ① substrate tank; ②influent pump; ③ air lift single SPNA reactor; ④ air pump; ⑤heater; ⑥ carrier

2.3. Operation conditions

3. Results & Discussion

3.1 Long-termoperation performance 3.2. Sludge characteristics

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1.2

(d)

(c)

(b)

No sludge discharge Inregular

sludge discharge

Ⅷ

ML

SS

(g/L

)

MLSS-Suspended

MLSS-Biofilm

MLSS-Total Mechanical stirring

treatment

No sludge discharge

(a)

ML

VS

S (

g/L

)

MLVSS-Suspended

MLVSS-Biofilm

MLVSS-Total

ML

VS

S/M

LS

S r

atio

Ratio -Biofilm

Ratio -Suspended

Ratio -Total

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20

40

60

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100 SV30 SVI

Operation time (d)

SV

30

(%

)

Phase

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SV

I (m

L/g

)

Ⅰ Ⅱ Ⅲ Ⅳ Ⅴ Ⅵ Ⅶ

The SPNA process was successfully operated

under NLR of 0.9 gN/L/d and NRE of 84%.

△NO3--N/△Nr is 0.10±0.01 during thestable

operation of SPNA system.

In phase 1, with NiRR/NARR ratios above 0.65,

the anammox reaction was the rate-limiting step

of total nitrogen removal.

Figure 3 The long-term operation performance of SPNA

systemFigure 3 Sludge characteristics of ALR-SPNA system.

The MLVSS concentration of the biofilm

during stable operation of SPNA is 4±0.5g/L.

After mechanical stirring treatment in phase

7, MLVSS concentration in the biofilm

recovered to 4.0g/L within one month.

3. Results & Discussion

4. Conclusions

3.3. Biofilm characteristics

Figure 5 Photo of biofilm. (a) day 84; (b)day 156; (c) day 214; (d)day 310; (e) day 360.

The formation of biofilm can be divided into four stages: the biofilm formation period (a and b),

the biofilm mature period (c), the biofilm aging period (d) and the biofilm reactivation period (e).

The cavity formed by N2 accumulation is the main factor causing the decline of biofilm activity.

Figure 6 SEM observation of biofilm. (a) blank; (b)biofilm formation period ; (c) biofilm mature period; (d)biofilm aging

period .

The pores on the surface of carrier are

conducive to the adhesion of anammox and

the rapid formation of biofilm

Sludge in the mature period of the biofilm

is aggregated as granules.

Ca and P concentrations increased from

biofilm mature period to biofilm aging period

Figure 7 EDX analysis of the biofilm. (a)biofilm mature period; (b) biofilm aging period.

The biofilm in low activity has the lowest VSS/SS ratio and anammox bacterial activity.

Figure 8 Analysis of the biofilm. (a) biofilm in aging period; (b) MLSS and MLVSS; (c) EPS; (d) SAA

Higher SAA of biofilm in high activity than biofilm.

The cavities generated by nitrogen gas and the accumulation of inorganic substances are the

main reasons for the decrease in NRE.

The SPN/A process was successfully operated under NLR of 0.9 gN/L/d and NRE of 84%.

Mechanical stirring can maintain the high activity of the biofilm.

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SA

A (

gN

/gV

SS

/d)

SAA

Biofilm Suspended Biofilm in

high activity

Biofilm in

low activity0

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Biofilm in

low activity

Biofilm in

high activity

Suspended

EP

S (

mg/g

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S)

PS

PN

Biofilm0

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6

PN/PS

PN

/PS

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4

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10

12

ML

SS、

ML

VS

S (

g/L

)

MLVSS

MLSS

Biofilm Suspended Biofilm in

high activity

Biofilm in

low activity

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MLVSS/MLSS

ML

VS

S/M

LS

S

High activity

Low activity

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NH4+-Ninf

NH4+-Neff

NO2--Neff

NO3--Neff

N i

n i

nfl

uen

t (m

g/L

)

Phase Ⅷ

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500(a)

Ⅶ

N i

n e

fflu

ent

(mg

/L)

(b)

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100 NRE

NRR

NR

E (

%)

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1.0

(c)

NR

R (

gN

/L/d

)

(d)

NiR

R、

NaR

R、

NA

RR

(gN

/L/d

)

NiRR

NaRR

NARR

(e)

NiR

R/N

AR

R

NR

R/N

AR

R

NiRR/NARR

NRR/NARR

3-

0.11

3

0

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40

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100

(g)

(f)FA FNA FNA 10μg/L FA 5mg/L

FA

(m

g/L

)

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FN

A (

μg

/L)

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DO

AR

Operation time (Days)

DO

(mg

/L)

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2.5

AR

(L/m

in)