养猪场废水外文翻译原文.doc

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Water Research 38 (2004) 3340-3348

Integrated real-time control strategy for nitrogen removal in
swine wastewater treatment using sequencing batch reactors
Ju-Hyun Kima,*, Meixue Chenb, Naohiro Kishidac, Ryuichi Sudoa
a Center for Environmental Science in Saitama, 914, Kamitanadare, Kisai, Saitama 347-0115, Japan
b State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences,
Chinese Academy of Sciences, Beijing 100085, P.O. Box 2871, China
c Department of Environmental Resources Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 1698555, Japan
Received 7 May 2003; received in revised form 29 March 2004; accepted 11 May 2004

Abstract

A new integrated real-time control system was designed and operated with fluctuating influent loads for swine wastewater treatment. The system was operated with automatic addition control of an external carbon source, using real-time control technology, which utilized the oxidation-reduction potential (ORP) and the pH as parameters to control the anoxic phase and oxic phase, respectively. The fluctuations in swine wastewater concentration are extreme; an influent with a low C=N ratio is deficient in organic carbon, and a low carbon source level can limit the overall biological denitrification process. Consequently, a sufficient organic source must be provided for proper denitrification. The feasibility of using swine waste as an external carbon source for enhanced biological nitrogen removal was investigated. The real-time control made it possible to optimize the quantity of swine waste added as the load fluctuated from cycle to cycle. The average removal efficiencies achieved for TOC and nitrogen were over 94% and 96%, respectively, using the integrated real-time control strategy.
r 2004 Elsevier Ltd. All rights reserved.

Keywords: Denitrification; External carbon source; ORP Real-time control; SBR; Swine wastewater

1. Introduction

Swine wastewater has previously been considered as
one of the major sources of nitrogen pollution dis-
charged into the environment. Traditional biological
removal of nitrogen was achieved by a sequence of
nitrification and denitrification processes. Since the
fluctuations in swine wastewater concentration are
extreme due to the varying practices of manure manage-
ment, in recent years, the real-time control process using
oxidation-reduction potential (ORP) and/or pH as
parameters (Lo et al., 1994; Plisson-Saune et al., 1996;

*Corresponding author. Tel.: [phone]; fax: +81-
480-70-2031.
E-mail address: [e-mail] (J.-H. Kim).


Chapentier et al., 1998; Fuerhacker et al., 2000) to
control the oxic and anoxic cycles of a system has
received much attention for swine wastewater treatment
(Ra et al., 1998, 1999; Tilche et al., 2001) in sequencing
batch reactors (SBRs). Compared to the traditional
process, real-time control strategy for a batch treatment
process using ORP and/or pH was self-adjusted to
various treatment conditions such as influent strength
and treatment status. This resulted in flexible hydraulic
retention time (HRT) from cycle to cycle (Ra et al.,
2000). The high and stable removal rate of nitrogen was
also achieved (Ra et al., 1998; Cheng et al., 2000).
Although real-time control strategy based on ORP
and/or pH has been applied to many swine wastewater
treatment systems, until now, the success of the systems
has not been convincing because much effort in the

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studies has dealt primary with the typical ORP and/or
pH profiles of a complete nitrification and denitrification
cycle and focused on aeration control (Ra et al., 1998;
Cheng et al., 2000). In fact, the control set-points on the
ORP or pH profiles would not have appeared in the
acclimated nitrate sludge (Kim and Hao, 2001; Kishida
et al., 2003).
Biological denitrification is known to occur by the
action of heterotrophic bacteria using available carbon
sources (John and Robert, 1985; Lee et al., 1995, 1997).
Because the influent with a low C=N ratio is deficient in
organic carbon and the low carbon source level can limit
the overall biological denitrification process, sufficient
organic source must be provided for proper denitrifica-
tion. Using the fermented swine waste (Lee et al., 1997)
or activated sludge (Ra et al., 2000) as an electron donor
for denitrification in SBRs has been suggested by several
authors, and such external carbon sources are viable
choices for enhancing SBR performance. However, any
excess external carbon added over the amount required
for the process appears in the effluent, and results in
increased cost of operation. Therefore, the addition of
the external carbon source should be optimized with the
fluctuation of wastewater.
The specific objective of this study was to establish an
integrated swine wastewater treatment system and
operating strategies suitable for the fluctuations of
influent loads. Particularly, under low C=N load cycles,
the system can optimize the addition of the external
carbon source to enhance nitrogen removal, as well as to

Relay box (On/ Off)

efficiently remove the pollutants from wastewater. For
this purpose, swine waste as external carbon source for
denitrification of nitrate was examined, and a pulsed
pattern of addition was determined. In addition, ORP
and pH as practical real-time control parameters were
evaluated. The SBR with an integrated strategy of real-
time control and a pulsed input control of swine waste
were designed and continuously operated for swine
wastewater treatment.

2. Methods

2.1. Sequencing batch reactor and operating strategies

The SBR was operated as shown in Fig. 1. The water
temperature was maintained at 2372 C. The reactor
was constructed using Plexiglas and had a working
volume of 9 L. A mechanical agitator was installed in it
for complete mixing. Air (2.4 L/min) for the reactor was
provided by an aerator through an air stone placed at
the bottom of the reactor. The reactor had five
sequences: influent feeding, anoxic phase, oxic phase,
sludge settling, and effluent transfer. The anoxic and
oxic times were automatically controlled by the compu-
ter depending on the variable process, while the times of
influent feeding, sludge settling and effluent decanting
were fixed at 5, 55 and 5 min, respectively. For every
cycle, 0.3 L of the influent wastewater was fed into the
reactor.

PC
I/O PC Card
Monitoring the time
variations of ORP
and pH

Effluent

Influent
Swine waste

ORP probe
pH probe
DO probe

Air


SBR Effluent bucket
Aerator Air stone
Fig. 1. Schematic diagram of a single batch sequencing reactor with real-time control strategy.

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3342 J.-H. Kim et al. / Water Research 38 (2004) 3340-3348

The ORP, pH and DO probes were inserted into the SBR. The output signal was directed to a computer. The influent pump, effluent pump, aerator, agitator and swine waste pump were controlled by a relay box connected by electrical cable.
Our experiment was started with high C=N ratio load
(TOC/TN>1.5) influent, which was collected after
screening treatment. After one week of operation, the
fluctuating influent was continuously used for 8 months
in our experiment. Swine waste as an external carbon
source was added into the SBR for complete denitrifica-
tion after a time determined by our experiment if there
was insufficient carbon source in the influent.
For the purpose of easy automatic control, a pulsed
input pattern of swine waste was used to compensate for
the external carbon source. During low C=N load
influent cycles, the diluted swine waste was pumped into
the SBR by a pulse-metering pump with a pulse of 1 g/
cycle, and the time interval between additions was
designed to be 10 min. If the quantity of swine waste
added was deficient for complete denitrification, the next
addition cycle was started, and when the nitrate knee
point, which indicates the end of denitrification,
appeared on the ORP profile, the addition of swine
waste was stopped. Therefore, the quantity of swine
waste added adapted to fluctuations in the wastewater,
and the optimization was easily achieved by the pulsed
input pattern.

2.2. Influent swine wastewater, waste and seed sludge

The swine wastewater used in this study was obtained
from a local farm in Saitama, Japan. The practical swine
wastewater with high C=N ratio (TOC/TN ratio: more
than 1.2) and low C=N ratio (TOC/TN ratio: less than
0.8), which was obtained before and after coagulation
treatment, respectively, was used alternately in the
experiment. The C=N ratio of the raw wastewater was
markedly changed by the separation of feces and urine.
The TOC/TN ratio in the wastewater was varied in the
range of 0.45-1.53. The swine wastewater was stored at
4 Cuntil required.
The swine waste was obtained from the same farm.
Prior to use, the waste was screened using a sieve with
0.5 mm mesh openings to remove large solids, diluted with tap water, and then used as an external carbon source in low C=N ratio load periods for complete denitrification. The characteristics of the diluted swine waste are listed in Table 1.
The average concentration of mixed liquor suspended solids (MLSS) in the system was maintained at approximately 7000 mg L 1. When the concentration of MLSS in the reactor was more than 8000 mg L 1, sludge was drawn out. During the experiment period, the average SRT was 32 days.

Table 1
Characteristics of the diluted swine waste
Parameters Mean Min-max Std. dev.
mg L 1 (n ¼ 15)
TOC 26,167 11,410-55,640 17,010
BOD5 90,280 46,370-172,200 31,850
TN 4529 2418-6882 1741
TP 2600 1500-3810 821
TSS 917 240-3950 43,720

2.3. Sampling and analytical methods

Parameters routinely assayed included TOC, BOD5,
total nitrogen (TN), NH4-N, NO3-N, NO2-N, total
phosphorous (TP), PO4-P, MLSS, mixed liquor volatile
suspended solids (MLVSS), and total suspended solids
(TSS). Track analysis that covered the entire cycle was
carried out at high and low C=N ratio load. Mixed-
liquor samples were taken during track analysis.
Analysis for NH4-N, NO3-N and NO2-N was carried
out for each track study. Analysis for BOD5, TSS,
MLSS and MLVSS was performed in accordance with
the standard method (APHA, 1995). The NH4-N, NO3-
N, NO2-N and PO4-P were analyzed with an ion
chromatograph (Yokogawa IC 7000). The TOC was
analyzed with a Shimadzu total organic carbon analyzer
(TOC 5000). TN and TP were analyzed with a total
nitrogen/phosphorous analyzer (TN-30, TP-30, Mitsu-
bishi Chemical Corp.)

3. Results and discussion

3.1. Real-time control point in high C/N ratio load cycles

In high C=N ratio load cycles, with real-time control
technology using ORP and pH as anoxic and oxic
control parameters, a treatment process can be operated
effectively without the addition of an external carbon
source to enhance the denitrification. During the initial
period with the high C=N ratio load influent relative
constant final effluents were obtained along with high
nutrient removal. The typical control set-points are
shown in Fig. 2. Point A is the feeding point, and after
5 min the anoxic phase was started. From the nutrient
profile, it can be seen that NO3-N is completely
denitrified to nitrogen gas through NO2-N within
75 min, using the influent organic materials as a carbon
source. Point B is known as the nitrate knee in the ORP
curve, which represents the complete removal of nitrate.
Reportedly, sulfate reduction that produces sulfides
starts just after denitrification is complete, and causes
this sudden decrease in the ORP (Plisson-Saune et al.,
1996). Point C signifies the beginning of the oxic phase.

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Influent
25

20

15

10

5

8.1

8.0
J.-H. Kim et al. / Water Research 38 (2004) 3340-3348

Anoxic phase Oxic phase
NH4-N
NO2-N
NO3-N

d
3343

150
100
50

7.9 A

7.8
B
7.7

7.6

7.5 pH
ORP
7.4

7.3
0 25 50 75 100 125 150
c

C

175 200 225
Time (min)


e

250 275 300 325

f

350
0
-50
-100
-150
-200
-250
-300
-350
375 400

Fig. 2. Real-time control points in high C=N ration load cycles (TOC/TN ratio of the influent: 1.4) A: Feeding, B: Nitrate knee point,

C and c: Beginning of the oxic phase, e: Ammonia valley point, f: End of the oxic phase.

The initial rise on the pH curve (from c point to d point)
is caused by carbon dioxide stripping from the system
and the rapid consumption of VFA that is produced
during the anoxic phase (Ra et al., 1998). Under oxic
condition, NH4-N decreases with time. Nitrate concen-
tration increases with time as ammonia is converted
through nitrification. The decrease in pH is caused by
the removal of ammonia from the system. Point e
represents the end of nitrification and it is known as the
ammonia valley. During nitrification, NH4-N is con-
verted into NO3-N, as shown in Eqs. (1) and (2) (EPA,
1975).
55NH4 þ 76O2 þ 109HCO3
-C5H7NO2 þ 54NO2 þ 57H2O þ 104H2CO3 ð1Þ

400NO2 þ NH4 þ 4H2CO3 þ HCO3 þ 195O2
-C5H7NO2 þ 3H2O þ 400NO3 ð2Þ

Alkalinity is required in the ammonia-nitrate oxida-
tion process (7.14 mg of alkalinity as CaCO3 to 1 mg of ammonia-N). The reduction of alkalinity and the acid production during nitrification decrease the pH. The complete removal of ammonia indicates the end of alkalinity consumption in the wastewater, hence the end of further pH decrease.

3.2. Real-time control point in low C/N ratio load cycles

The designation of a control point in low C=N ratio
load cycles was very important for integrated real-time
control strategy. The track analysis with low C=N load
influent is shown in Fig. 3. Point A is the beginning of
the anoxic phase. From the nutrient profile, it can be
seen that NO3-N that is produced from nitrification
during the previous oxic phase is slowly denitrified using
the carbon source provided by the feed. After 2 h,
complete denitrification was not reached due to insuffi-m
pH