Wastewater characterization and its impacts
to the performance of wastewater treatment
plant in Hanoi City, Vietnam

T. T. V. Nga1) , V. D. Canh1) and P. A Zuber 2)
1- National University of Civil Engineering, Vietnam
2- Biwater International Ltd, United Kingdom

1

ContentIntroductionObjectives of the study

Methodology and scope of the studyResults and discussions

2

Urban sewerage systems






Among existing systems, the proportion of wastewater flow being
conveyed by the combined sewerage systems (CSS) is 92%,representing a total treated volume of ~6000,000 m3/day.
By 2013, there were 17 municipal Wastewater Treatment Plants(WWTP) and at least 31 WWTPs under construction, design andoperation.
Many of the recently installed WWTPs in Vietnam were designed
based on typical wastewater characteristics for Combined Sewage
Systems and include parameter values such as BOD5: 150-250
mg/l, COD: 250-350 mg/l, and NH4-N: 15-35 mg/l.
It is reported that in operation they receive significantly different
influent loads.

3

Urban drainage system

A combined system collecting industrial ,domestic wastewaters as well as themanagement of storm water and surface
water run-off.
Most urban house have a flush toilet witha connection to the septic tankEffluent (septic) is discharged into sewerlines and semi-open drainage canals thenrivers.
Wastewater quality and quantity areseasonal fluctuatedAn understanding of the nature ofwastewater is essential in the design andoperation of collection, treatment, anddisposal facilities.

Urban sewage system – Combined drainage system

Catch ment
basin A

Streetsewers

Urban canal,
riversMaintrunksPSRIVER

Equalizationlake

Catchment
basin B5Hanoi sewage treatment system
Vietnamese discharge
Wastewater
standard QCVN40/2011- BTNMTParameters(designvalue) (mg/L)
Class AClass BCOD

225-350

50100

BOD

150-250

3050TSS

180-250

50100

T-N

25-40

2040

NH4-N

15-35

5

10

T-P

64

6Current applied technologies:
AO/AAO processes.

SBR

This study therefore was conducted tocharacterize wastewater quality in
Hanoi City, Vietnam.

Objectives and ScopeThis study investigate the influent to Hanoi’s first large scale wastewater
treatment facility (Yen So WWTP).
This WWTP collects influent sewage from the Kim Nguu open channelsewer (11 km in length) feeding to the 200,000 m³/d WWTP.
Catchment basin is a densely-populated area of ~596 ha.
The results will be reviewed in relation to the achievement of therequired consent and the potential impact the nature of the influent will
have on the WWTP design requirements.

7

Yen So WWTP
Return Liquors

PTW

SBRs

(PreliminaryTreatment Works)(Sequencing BatchReactors)

Set River
IntakeChemicalDosing Plant

WASMIPS(Main Inlet PumpingStation)

Yen So Park
Sewer(Waste Activated Sludge)

Kim NguuRiver Intake

Discharge to
Kim Nguu River

Odour Control

Discharge toYen So LakeUV Treatment(Ultra Violet)

ChemicalDosing Plant

UF Membrane
Plant(Ultra Filtration)

Sludge Line

Odour Control

Odour Control
Polymer
MakeupWAS Storage(Waste ActivatedSludge)

Service Water

Odour Control

Polymer
Makeup

Biogas System
GasFlareSludge
Thickening

Thickened
SludgeStorageCapacity: 200,000 m3/day

Activated Sludge Process (SBR)

Digested
SludgeStorage

Anaerobic
Digestion

8Sludge
Dewatering

DewateredSludge
Storage

Filtrate SBR

ChemicalDosing PlantMethodologyThe sampling of the Kim Nguu inlet to Yen So WwTP

Grab samples were collected along the Kim Nguu canalSamples of the WwTP performance (dailycomposite samples).
9Influent water quality
Parameter
BOD
COD
TSS
TKN
NH4-N
Total Phosphorous
Relationships:
COD:BODTSS:BOD
NH4-N of TKN
BOD:NH4-N

Kim Nguu at WWTP Intake
Average
5%ile
95%ile
mg/l
mg/l
mg/l
45
2278
115
74
167
46
29
79
39
21
59
36
1756
8.8
4.3
11.8
2.9
1.3
90%
1.4

1.5
0.4
96%
0.5

5.1
2.579%
2.6

Typical Design Data
LowerUppermg/l
mg/l
120
350
250
600
100
450206512454122.1
0.8
60%
7.8

3.4
1.369%
10Low BOD (45 mg/l), low TSS (46 mg/l), a relatively high nitrogen (TKN
40 mg/l; NH4-N 36 mg/l), and a high proportion of NH4-N (90%).
COD:BOD ratio: 1.5 - 5.1 (average 2.9)
BOD:NH4-N ratio of 1.4  A significant impact on the design andperformance of a wastewater treatment plant
10Influent water quality
A 250
consistent relationship BOD vs TSS, and low BOD,200TSScontent confirm TSS is largely independent of the150
BOD
and associated with fine colloidal material that is100slow
to settle
250

TSS (mg/l)

COD (mg/l)

20050150
1005000020406080

100120014020406080

100120No clear relationshipbetween BOD and NBOD
compounds
BOD (mg/l)(mg/l)
80

NH4-N (mg/l)

80

TKN (mg/l)

14060
40

y = 1.0094x - 3.4754
R² = 0.979

60
40

A clear linear relationship between TKN vs NH4-N2020
nitrogen is largely soluble andreadily available.
00020406080

BOD (mg/l)

10012014002040

TKN (mg/l)

6080

Influenced by wet weather conditions
Kim Nguu Influent to Yen So WWTP
Wet Season (April - October)
Dry Season (November - March)
Average
5%ile
95%ileAverage
5%ile
95%ile
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
40
2169
47
2284
109
72
157
11876
179
45
3272
46
2884
31
1750
43
28
60
27
14
47
40
25
57
7.2
3.2
10.4
9.7
7.7
12.3

Parameter

BOD
COD
TSS
TKN
NH4-N
Total Phosphorous
Relationships:
COD:BODTSS:BOD
NH4-N of TKN

3.0
1.387%

1.50.674%

5.32.496%
7 day Ave. NH4-N (mg/l)

7 Day Ave BOD (mg/l)

1601401201008060
40
200050100

1502001.50.486%2.9
1.293%

4.8
2.696%

50
45
40
35
30
25201510500250

50

100

15020012

7 Day Totalised Rainfall (mm/d)

7 Day Totalised Rainfall (mm/d)

250

Influenced by wet weather conditions



Most parameters have lower concentrations during the wet season
due to freshwater ingress.
The exception is TSS, where there is no measurable difference inbetween the dry and wet seasons, suggesting that any dilution effectfrom the ingress is compensated for by additional scoured solids orrun-off solids. The solids reaching the intake of the works are largely
fine colloidal solids with low settling characteristics
In wet season, TKN and NH4-N levels are reduced on average by 12
and 13 mg/l respectively
On average 10 mm of rain will result in a 1.5 mg/l reduction of NH4-N,
and 2.4 mg/l reduction of BOD

Retention time in collection system
120

Average BOD and NH4-Nin Kim Nguu canal were 17and 10 mg/l respectively,
higher compared to its
tributaries
The trends for eachparameter followed similar
trends in concentration
throughout the year.

806040200

Kim Nguu

Tributaries

Kim Nguu

Tributaries

60NH4-N (mg/l)

BOD (mg/l)

100

50
4030
20
10014

Seasonal changes
100

Influent (mg/l)



80
60
40
200Dec Jan Feb Mar Apr May Jun

BOD

Jul Aug Sep Oct Nov Dec Jan



NH4-N

7Jan - Apr: the average BOD andNH4-N drop and COD:BOD ratio
increase. Low BOD and still
relative high NH4-N represents asignificant total nitrogen treatment
challenge
May-Aug: reduction of soluble
NH4-N. BOD increase for the first
2 months, and BOD dropping inJuly-Aug.

Influent (mg/l)

6543210Dec Jan Feb Mar Apr May Jun

COD:BOD

Sep-Dec: BOD and NH4-N
increase at a rate 1.8 and 1.3
mg/l-week. But BOD:N ratio isless than the theoretical ≥ 2.5-3.0
BOD:N ratio normally required tosustain denitrification.

Jul Aug Sep Oct Nov Dec Jan

BOD:NH4-N15Treatment performance

When COD:NH4-N ratio isreduced, and particularly < 4.0,effluent NO3-N increase when theinfluent ammonia levels are alsohigh (≥40 mg/l) insufficientorganic material in influent tosupport the required level ofdenitrification.
As influent COD:NH4-N reduced
further, NH4-N in effluent may
also not meet the requirements.

16

Effluent NO3-N (mg/l)

When high COD:NH4-N, there issufficient organic material to effectdenitrification to satisfy the TNrequirements.

14121086420
23Influent NH4-N (mg/l)

456710Influent COD:NH4-N
1020304050606050

Effluent TN (mg/l)

40

QCVN40, B class

302010QCVN40, A class

040909Jan1640969
Mar41030
41214 Dec
May 41091
July 41153
Sept Oct

Total Nitrogen
Lower Forecast

Upper Forecast
QCVN 40:2011

Conslusions






The nature of sewage in combined systems in Vietnam cities can be significantly
different to the norms specified for wastewater treatment . There is insufficientorganic material to sustain denitrification process, requiring supplemental BOD inorder to guarantee compliance.
Data shows the impact of an extended dry season on reducing the BOD:NH4-N
ratio and adding further risk to the nitrogen compliance.
Long retention times in collection channels can lead to the settlement anddegradation of organic materials. Additionally, with the preference and obligation
to utilise septic tanks, the organic load is further reduced and the release ofsoluble nitrogen could be enhanced
The challenge to the design and regulatory process is the imposed compliancestandards in Vietnam. It is difficult to achieve TN standard without thesupplement of external BOD.
For Vietnam there has been a gradual relaxation of the compliance requirements
for nitrogen management, but potentially this has not progressed far enough tomatch the current available sewage and treatment technologies.