URBAN STORMWATER QUALITY AND LOAD ESTIMATION FROM URBAN RESIDENTIAL AREA IN

SKUDAI, JOHOR, MALAYSIA

Siti Nazahiyah Bte Rahmat

Faculty of Civil and Environmental Engineering Universiti Tun Hussein Onn Malaysia (UTHM)

INTRODUCTION

Two main impacts of urbanization.

First the hydrology is modified causing more rapid flow

path;

Second, increase of human activities that adds

pollutants.

NPS - need to estimate NPS loads to the receiving watercourses

Crucial for sustainable water resource management

OBJECTIVES

Specifically the study will:-

i. Quantify loadings of pollution from the residential catchment

ii. Determine the first flush phenomenon

METHODS

I. Measurement of rainfall, streamflow and water quality

II. Analysis of samples for BOD5, COD, SS, Nutrients (NO3-N, NO2-N, NH3-N, P).

STUDY SITE

Taman Universiti

N

TAMAN UNIVERSITI – JALAN PERTANIAN

Study catchment

LegendResidential area Rain gaugePervious area Catchment boundaryPavement roads Drainage network

Monsoon drain Scale 1 : 4,200

Catchment outletN = 1º 32’ 24”E = 103º 37’ 6”

Figure 1: Residential catchment

Physiographical conditions of sub catchment

Land useLow cost residential area: high density single-storey

houses

Area (ha) 3.34

Elevation (mas1) 45.5 - 66

Slope (%) 2.53

Drain gradient (%) 1.08

Drainage density (km/km2) 78.3

Outlet for the residential catchment

Sampling point

ANALYSIS AND RESULTS

Rainfall characteristics of monitored storms

Event measuredRainfall (mm)

Intensity (mm/hr)

Days since last storm (hr)

* 8-Nov-03* 11-Nov-0311-Jan-042-Mar-044-Mar-046-Mar-04

12-July-048-Sept-044-Nov-0427-Dec-04

--

1.521.5218.82.8196.8658

--

3.52.5169.3168.8279.6

--

12023 45

46.4245021-

Note:* rain gauge was not installed yet

EVENT MEAN CONCENTRATION (EMC)

EMC – total constituent mass discharged, during an event, divided by the total runoff volume of the event.

EMC = M = QiCi / Qi (1) V

Qi is the time - variable flow and

Ci is the time - variable concentration

Event Means Concentration (EMC)

Site Events BOD5

(mg/l)

COD(mg/l)

SS(mg/l)

NO3-N

(mg/l)

NO2-N

(mg/l)

NH3-N

(mg/l)

P(mg/l)

Residential 8-Nov-03 73 238 274 0.69 0.02 0.66 1.11

11-Nov-03 54 136 259 0.07 0.03 0.73 0.6

11-Jan-04 85 296 1024 0.91 0.13 8.7 7.3

2-Mar-04 190 675 742 3.9 0.06 7 7.8

4-Mar-04 123 316 259 3.3 0.07 9.12 1.24

6-Mar-04 156 728 374 1.7 0.82 3.6 3.44

12-July-04 68 181 85 6 - 0.37 0.93

8-Sept-04 39 98 152 0.17 - 0.37 4.52

4-Nov-04 47 118 21 3.7 - 0.8 0.01

27-Dec-04 113 320 405 3.1 - 3.7 1.6

SMC 95 311 364 2.4 0.1 3.5 3

Pollutographs and hydrographs in the residential catchment

0

2

4

0.0 0.5 1.0Storm Duration (hr)

Con

cent

ratio

n (m

g/L)

0

20

40

Flo

w (

l/s)

NO3-N

Flow

Residential - 6 March 2004

0

0.5

1 Rai

nfal

l (m

m)

0

100

200

0.0 0.4 0.8Storm Duration (hr)

Con

cent

ratio

n (m

g/L)

0

75

150

Flow

(l/s

)

BOD

Flow

Residential - 8 September 2004

0

2

4

Rai

nfal

l (m

m)

0

300

0.0 0.4 0.8Storm Duration (hr)

Con

cent

ratio

n (m

g/L)

0

75

150

Flo

w (

l/s)

SS

Flow

Residential - 8 September 2004

0

2

4

Rai

nfal

l (m

m)

0

300

600

0.0 0.4 0.8Storm Duration (hr)

Con

cent

ratio

n (m

g/L)

0

75

150

Flo

w (

l/s)

COD

Flow

Residential - 8 September 2004

0

2

4

Rai

nfal

l (m

m)

POLLUTANT LOADING

Calculated by the following equation:

L = V x EMC (2)

where, L is unit pollutant loading rate (kg/ha),

V, total volume of flow over entire event duration (m3)

EMC, event mean concentration (mg/l)

Event pollutant loadings for the residential catchment

Parameters Loading (kg/ha)

Range Mean

BOD5

COD

SS

NO3-N

NO2-N

NH3-N

P

0.5-16.5 4.9

1.2-27.5 9

2.2-22 7.5

0.001-1.5 0.35

0.0003-0.01 0.004

0.013-1.2 0.2

0.002-0.14 0.05

FIRST FLUSH PHENOMENON

L = m(t) / M (3)

F = v(t) / V (4)

where L is dimensionless cumulative pollutant mass; m(t) is pollutant mass transport up to time t (g); M is total mass of pollutant over the entire event duration (g); F is dimensionless cumulative runoff volume; v(t) is flow volume up to time t (m3) and V is total volume of flow over the entire event duration (m3).

LITERATURE REVIEW

Bertrand et al. (1998) defined first flush by the fact that at least 80% of the pollutant mass is transported in the first 30% of the volume.

Meanwhile, Wanielista and Yousef (1993) proposed that 50% of the pollutant mass is transported in the first 25% of the volume.

Mass Volume, M(V) ratios of BOD, COD, SS, NO3-N, NO2-N and NH3-N in the residential catchment

BOD - Residential

0.0

0.2

0.4

0.6

0.8

1.0

0.0 0.2 0.4 0.6 0.8 1.0

Dimensionless Cumulative Flow rate

COD - Residential

0.0

0.2

0.4

0.6

0.8

1.0

0.0 0.2 0.4 0.6 0.8 1.0

Dimensionless Cumulative Flow rate

SS - Residential

0.0

0.2

0.4

0.6

0.8

1.0

0.0 0.2 0.4 0.6 0.8 1.0

Dimensionless Cumulative Flow rate

NO3-N - Residential

0.0

0.2

0.4

0.6

0.8

1.0

0.0 0.2 0.4 0.6 0.8 1.0

Dimensionless Cumulative Flow rate

NO2-N - Residential

0.0

0.2

0.4

0.6

0.8

1.0

0.0 0.2 0.4 0.6 0.8 1.0

Dimensionless Cumulative Flow rate

NH3-N - Residential

0.0

0.2

0.4

0.6

0.8

1.0

0.0 0.2 0.4 0.6 0.8 1.0

Dimensionless Cumulative Flow rate

Cumulative load at 20-30% of the runoff volume in the residential catchment

BOD COD SS NO3-N NO2-N NH3-N P

MinMax

Mean

0.20.590.4

0.150.690.42

0.150.780.47

0.140.490.3

0.140.190.17

0.230.530.38

0.230.430.33

CONCLUSION

By comparison to the Interim National Water Quality Standards for Malaysia, the stormwater quality from the urban residential catchment was severely polluted with major parameters generally exceeded the acceptable limits for class V water;

EMC for all parameters were found to vary greatly between storms;

FF phenomena were detected in this study. The relative strength of the first flush was: SS> COD> BOD5> NH3-N> P> NO3-N> NO2-N.

A rain gauge installed on roof top in the residential catchment