Prospects and Limitations of Surface Runoff Quality Management in the Republic of Serbia - Page 02

 

 

Quality of Surface Runoff

Difficulties in establishing storm water runoff pollution loads are due to the random character of precipitation events and large spatial and temporal variations of rainfall intensity, runoff rates and contaminant concentrations. Establishment of hydraulic and pollution loads requires measurements of rainfall, flow rate (runoff) and analyses of pollutant concentrations in water samples. The collected data is analysed and represented in the form of storm hydrographs and storm pollutographs or load-graphs.

Research of runoff quality in urban and suburban watersheds indicates the presence of the following contaminants:

  • Organic pollution, expressed as a 5-day biochemical oxygen demand (BOD5), is present in rather low concentrations in runoff from impervious surfaces (roads, pavements, roofs), but concentrations can be elevated in runoff from gardens, parks or agricultural areas;
  • Suspended solids (SS) are the most pronounced pollutant present in urban surface runoff, and its concentrations depend on land use, storm intensity and duration;
  • Heavy metals, such as copper, lead, cadmium, nickel, chromium and zinc, are also present in urban surface runoff. Concentration levels of these pollutants exhibit good correlations with concentrations of suspended solids, and they vary in a wide range depending on land use and motor traffic intensity patterns in the catchment area. High concentrations of heavy metals generally correspond with high motor traffic intensity patterns.
  • Oils and fats are temporarily present in surface runoff and their presence is an indication of accidental pollution (oil and fuel leaks from motor vehicles, rinsing of oil from surfaces in industrial plants where accidental oil spillage occured, etc.);
  • Nitrogen and phosphorus are present in higher concentrations in runoff from gardens, parks or agricultural areas;
  • Other specific contaminants occurring in surface water runoff vary based upon land use, soil composition, air quality and other factors.

Proper results analysis and interpretation requires knowledge of runoff quality parameters of the drainage basin (land use, soil types, etc.) as well as spatial variability. The presence of high pollutant levels can be explained by the presence of industrial facilities in the area where measurements are carried out, the use of road antifreeze agents during the winter months, and numerous other factors. The quality of the storm water runoff from various types of land use areas are given in Tables 2 and 3 below.

 

Table 2: Typical Urban Areas and Pollutant Yields (Burton and Pitt, 2002)

Pollutant

Land Use (lb/acre/year)a

Commercial

Parking Lot

Residential - Density

Highways

Industry

Parks

Shopping Center

High Medium Lowb

Total Solids

2100 1300 670 450 65 1700 670 NAc 720
SS 1000 400 420 250 10 880 500 3 440
CI 420 300 54 30 9 470 25 NA 36
TP 1.5 0.7 1 0.3 0 0.9 1.3 0.03 0.5
TKN 6.7 5.1 4.2 2.5 0.3 7.9 3.4 NA 3.1
NH3 1.9 2 0.8 0.5 0 1.5 0.2 NA 0.5
NO3 + NO2 3.1 2.9 2 1.4 0.1 4.2 1.3

NA

0.5
BOD5 62 47 27 13 1 NA NA

NA

NA
COD 420 270 170 50 7 NA 200

NA

NA
Pb 2.7 0.8 0.8 0.1 0 4.5 0.2

0

1.1
Zn 2.1 0.8 0.7 0.1 0 2.1 0.4

NA

0.6
Cr 0.15 NA NA 0 0 0.09 0.6

NA

0.04
Cd 0.03 0.01 0 0 0 0.02 0

NA

0.01
As 0.02 NA NA 0 0 0.02 0

NA

0.02

a   The difference between lb/acre/year and kg/ha/yr is less than 15%, and the accuracy of the values shown in this table cannot differentiate between such close values
b   The monitored low-density residential areas were drained by grass swales
c   NA = Not available

 

Table 3: Range of pollution concentration in urban runoff (Metcalf & Eddy, 2002)

Parameter

Concentration

Suspended Solids (mg/l)

67 – 101

BOD5 (mg/l)

8 – 10

COD (mg/l)

40 – 73

Coliforms (number/100 ml)

10000 – 100000

TKN (mg N/l)

0,43 – 1,00

NO3 (mg N/l)

0,48 – 0,91

Total P (mg P/l)

0,67 – 1,66

Cu (mg/l)

0,027 – 0,033

Pb (mg/l)

0,030 – 0,144

Zn (mg/l)

0,135 - 0,226