Energy Consuming Comparison of Wastewater Treatment Technologies through Life
Cycle Assessment
A Case Study of Sequencing Batch Biofilm Reactor
筑波大学生命環境研究科 孫 爽

1.

氷鉋揚四郎

Introduction

In the summer of 2010, it is reported that the power shortage of China is about 15% of whole electricity
production, and this trend is believed to be more serious in the coming future due to coal supplement
shortage and global price growth. In 1996, the centralized processing rate of municipal wastewater in China
was only 11.4%, and will reach to 40% in 2010, and over 1,000municipal wastewater treatment plans(MWWTP) will be constructed in future and most of them will be small and mid-scale ones (Wei, 2000).
For a general wastewater treatment plan, energy, usually is electricity, takes 60%-70% of total maintenancecost (Tan, 2011).
From the view of life cycle, from construction stage to the final demolishment stage, the energy
consumption is a key factor which could influence the resource, environment, and sometimes it also could
lead social impacts. However, the traditional method has been unable to reflect the whole process of energy
utilization due to its limited boundary. The traditional method usually is based on the economic andtechnology aspects, it could provide the view from production stage but not big one.
Life Cycle Analysis (LCA) is a new system of environmental impact assessment techniques and methods,
which uses the technology facilities as the main line to collect, identify, quantify, analyze and assessresources consumption and the data and information of environmental impact of products throughout thelife cycle, provides an environmental assessment tool of comprehensive, accuracy information
This paper try to identifies and analyzes quantificational the whole energy consumption process fromdesignation, exploitation and manufacturing of raw material, construction, handling, running,reconstruction and expansion of wastewater plant, abandoning and back out of Life Cycle Assessment(LCA). Meanwhile this study tries to compares this technique to traditional activated sludge process(TASP), which aims to bring out new technical economy and environmental assessment method.
2.

Objective and Scope

In this paper, two indicators have been analyzed and compared based on the energy consumption of thewastewater treatment under different technology: (1) The energy consuming of wastewater treatment isconverted into electric energy (KWh) or heat energy (KJ), and the consumed energy for treating per unit
polluted water capacity(m3) or energy consumption ratio; (2) The whole energy consuming every year ofdifferent wastewater treatment technology has been calculated in terms of the same scale and similar water
quality condition.
In this study, Sheng Jian wastewater treatment plant is taken as the study object. The capacity of Sheng Jian

wastewater treatment plant is 10,000m3/d, a sequencing batch biofilm reactor with intelligent control
system (ICSBBR) is adopted. The logical treatment process of this plant is as shown in Figure 1. Maintechnology parameters of ICSBBR as following: total hydraulic retention time (HRT) is 7 hr. The
characteristics of designed raw domestic sewage were (average value): pH (5.9-7.5), COD (200-250mg/L),
BOD5 (100-150 mg/L), suspended solids SS (100-150mg/L), (NH3-N (25-35 mg/L), and TP (4-6 mg/L).
The reactor was seeded with activated sludge collected from Qing He Municipal Wastewater Treatment
Plant, Beijing, China, which had a mixed liquor suspended solids (MLSS) and SS content of 1638 mg L−1
and 3562 mg L−1, respectively.
2.1. Intelligent Controlled Sequencing Batch Biofilm Reactor
ICSBBR is a more advanced technology which could reach higher energy utilization rate by theinformation system. System will adjust aeration time based on the data of oxygen utilization rate collectedby sensors automatically. Well-designed software will guarantee the dissolved oxygen (DO) maintains in
the required level. Therefore, treatment and energy consumption rate could be improved respectively.
According to the previous study, a stable performance of ICSBBR under hydraulic retention time (HRT) of
7 h, at which point the removal efficiencies of NH3-N, TP and COD reached 99%, 100% and 96%,
respectively (Ding 2011). When compared with conventional SBBRs, the SBBR controlled by the ICS
reduced the HRT and total aeration time by 56% and 50% (Ding 2010), respectively, and achieved better
performance at removing the COD.
When carbon nitrogen （C/N）ratio is 12.5, an experiment scale ICSBBR could reach the best performanceand COD, TN, NH3-N removal efficiency is 94.8%, 87.4% and 90.1% respectively (Ding, 2011).
2.2. The unit of LCA appraised function
According to the general urban planning, most of the city’s wastewater treatment plants need to be rebuilt
and updated to some extent with the increase of wastewater quantity and the increase of the discharge
standard. For Sheng Jian wastewater treatment plant, the energy consumption problem should beconsidered in a 20 years’ runtime.
It is well known that the consumptions and functions of a wastewater treatment plant’s facilities have scaleeffects. The capacity of Sheng Jian wastewater treatment plant is 10,000m3/d, which is a typical wastewater
treatment plant for small or middle town. This article uses such scale as the function unit for LCA analysis
to compute the input and output of the wastewater treatment system. The traditional activated sludge
process (TASP), which is used as a contrast, also applies this scale as the function unit, in order to makethem comparable.
3.

The detailed analysis list of energy consumption

3.1. The input-output of wastewater treatment facilityDuring the life cycle of wastewater treatment facility, the energy, resource and the processing object input

by environment and the contamination output to environment and their influence, are shown in Figure.2 .
The resources input by the environment include the various raw materials as well as natural resources formaterial production, such as water, air, natural ore etc; raw wastewater is the research object. The energy
sources include coal, petroleum and the electric energy etc., which are converted into Joule conformably.
Materials and energy may be used in the whole life cycle is shown in table 1.

Table 1 Materials and energy consumption in
MWWTP
Stage

Raw material

EnergyConstruction

Steel, iron,cement, sand,water, PVC,copper,clay, bitumen,
epoxide resin
etc.

Transportation,construct,mechanical
DissipationsOperation

Medicament etc.

Powerconsumption, fuel,equipment
dissipation

Demolishment

Topsoil, fillingmaterial etc.

mechanicaldissipations, fuel, etc.

3.2.
The energy
construction phaseconsumption

intheTable 2 material and energy of construction stage(106 Kwh)
ICSBBR
Total energy of
raw material
Total energy oftransportation

1.63

1.74

0.160.10

0.323

0.51

2.113

2.35

construction
Total energy
consumption

According to quantities analysis and concerned
standards, the building materials quantity of
ICSBBR can be calculated and the productionenergy consumption can also be quantified basedon its material quantity and energy consumption
for production. The construction energy
consumption can be counted according to theconstruction area, and the construction energy
consumption per unit area; the energy consumption
for transportation building material can be counted
according to the consumption amount of building
material, transportation mileage, and energy
consumption for transportation per unit.
3.3.
stageEnergy consumption

in operation

TASP

Total energy
consumption for

The energy consumption during the construction
phase includes raw material production,construction and transportation. The total energy ofsome kind of material is consisted of its natural
calorific value and the energy consumption forproduction. Unified energy unit is adopted toquantify the different energy.

The material consumption during running phase oftreatment facilities is much low. The medicament
consumption is the main portion. The energy
consumption in this phase includes the power for
wastewater treatment, the fuel and equipment loss
for transportation, etc. Among them, the power
consumption for wastewater treatment always
occupy the total energy consumption more than85%; in which, the electricity consumption of
aeration systems is over 88.5% (Tan 2011).
ICSBBR
could
reduce40%
electricity

consumption rather than the traditional SBBR
system due to its energy reduction design.
3.4. The
energydemolishment stage

consumptionoftheThe energy consumption in the demolishment
phase is related with the machine equipment fordemolishment mostly, normally, which includes
two parts: demolishment and transportation. The
Table 3: The list of main electrical equipment andenergy consumption of process
Stage orprocess

ActualEquipment

Powerenergy consumption of demolishment is 90% of
the energy consumption of construction according
to concerned documents (Yang, 2000). The energy
consumption of transportation for soil and fillingmaterial is calculated by construction area, theaverage density of soil and filling material (2.0kg/m3) and average transportation mileage (20 km).

Table 4: total energy consumption and materialconsumption of ICSBBR and TASP from LCA(106 Kwh)power
consumption

StagePrimary
Treatment

Construction

First Lifting

Lifting pump

1.5 Kw

1.5 Kw

GridGrid machine

1.5 Kw

1.5 Kw

Lifting pump

0.75 Kw

0.75Kw

SecondLifting

Operation

Secondary
Treatment
Stir

Stir pump

2.2 Kw *4

8.8 Kw

Aeration

Ventilators

4 Kw * 28 Kw

Demolishment

Advancedtreatment
Inverse flow
FilterPump
Filter Pump

5 Kw * 2
2.2 Kw *2

10 Kw

treatment

pumping
Sludgetransportation

Sludge Pump

0.75 Kw

0.75 Kw

1.1 Kw

1.1 Kw

Beltdewatering

Total

3.5 Final result

TASP

Material
consumption

2.31

2.25

Energyconsumption

2.113

2.35

Material
consumption

2.34

4.09

Energyconsumption

5.56

17.11

0.01

0.01

0.441

0.46

12.653

19.92

Material
consumption
Energyconsumption

4.4 Kw

SludgeSludgeTotal energy
consumption

ICSBBR

machine36.8 Kw

It can be concluded from the Table 4, both of theconstruction consumption and energy consumptionof operation stage are lower than the TASP becauseof the intrinsic property of ICSBBR. As far as
energy consumption, energy utilization andenvironmental impacts caused by the energy
produced process; the environmentalism ofICSBBR is superior clearly to the TASP. The totalenergy consumption and material consumption isshown in table 4.

4.

Conclusion

During the life cycle of wastewater treatment plants, energy consumption is a key factor of cost. To reduceor utilize energy efficiently is very important, which could also reduce other environmental impacts. Basedon ideas of LCA, from the very beginning of construction stage to the final demolishment stage, several
methods are put forward to improve energy efficiency. This paper, applied the thought of LCA, recognizes
and quantizes the ICSBBR in Sheng Jian wastewater treatment plant in Yun Nan province, China, from thestage of design, exploitation and machining of raw material to wastewater plant construction, running,reconstruction or extension, and demolishment, which had been compared with the TASP. The results show,
the energy consumption of ICSBBR during each stage is lower than ordinary means of active sludge; andwith intelligent mode is applied to the operation stage, the energy consumption is much lower than theTASP and even than traditional SBBR (Ding 2011). The results show that the ICSBBR, because of its small
land occupation, simple maintenance, little foul smell, and environmentalism, is superior clearly to theTASP.
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Appendix

Figure 1 ICSBBR process flow

Figure 2 The input output flow of ICSBBR wastewater
treatment