**4.3. Impact of seasonality on wastewater**

Careful analysis of rainfall and pollution loading rates (BOD & COD) were following reverse interaction throughout the study period. The rainfall recorded in Satrameel field station located in the study area has shown an increasing pattern during monsoon months from July to September (Figure 5). The lowest values for both BOD and COD were observed during the wet period of monsoon when increased surface runoff diluted the pollutions (least in Septem‐ ber), while higher concentrations were recorded during dry periods (highest during March) when after monsoon even base flows started decreasing (Figure 6). Although higher rainfalls during June to September 2011 had caused a lot of surface runoff that resulted in lowering of the pollution levels, nitrate and nitrite increased in amount due to the washing out of human, poultry, and animal wastes.

**Figure 5.** Monthly rainfall pattern during study period.

**Wastewater Parameters Permissible Limits**

Biochemical Oxygen Demand 50 mgl-1 Chemical Oxygen Demand 100 mgl-1 Electrical Conductivity 1,000 μScm-1 pH 6.0–8.0 Nitrate 20 mgl-1 Nitrite 2 mgl-1 Total Phosphates 10 mgl-1 Total Dissolved Solids 1,200 mgl-1

**Table 4.** Permissible limits of wastewater parameters as per NEQ standards.

**Table 5.** Estimated loading rates of BOD, COD, TP, Nitrate, Nitrite, and TDS.

**4.3. Impact of seasonality on wastewater**

poultry, and animal wastes.

The values of all these parameters were lowest in the Shahdara catchment.

**BOD (kg.day-1)**

**COD (kg.day-1)**

Hathala catchment 547 1052 16 50 7.25 6,649 Kiani road catchment 940 1513 22 49 1.29 8,225

Total 2,296 3,875 53 141 4.73 19,653

Shahdara catchment (before bridge) 98 158 3 6 0.17 963 Col. Amanullah Road catchment 680 1117 11 30 0.29 2,961

Shahdara catchment (after bridge) 31 35 1 6 1.73 855

Pollution parameters such as BOD, COD, phosphates, and TDS were being discharged in large quantities (940, 1513, 22, and 8,225 kg.day**-1** respectively) from Kiani road catchment, while nitrate (50 kg.day**-1**) and nitrite were being added (7.25 kg.day**-1**) from the Hathala catchment.

Careful analysis of rainfall and pollution loading rates (BOD & COD) were following reverse interaction throughout the study period. The rainfall recorded in Satrameel field station located in the study area has shown an increasing pattern during monsoon months from July to September (Figure 5). The lowest values for both BOD and COD were observed during the wet period of monsoon when increased surface runoff diluted the pollutions (least in Septem‐ ber), while higher concentrations were recorded during dry periods (highest during March) when after monsoon even base flows started decreasing (Figure 6). Although higher rainfalls during June to September 2011 had caused a lot of surface runoff that resulted in lowering of the pollution levels, nitrate and nitrite increased in amount due to the washing out of human,

**TP (kg.day-1)**

**Nitrate (kg.day-1)**

**Nitrite (kg.day-1)**

**TDS (kg.day-1)**

**Locations**

190 Wastewater Treatment Engineering

Figure 5. Monthly rainfall pattern during study period.

Figure 6. Temporal behavior of BOD, COD, TP, nitrite, and nitrate in the study area. **Figure 6.** Temporal behavior of BOD, COD, TP, nitrite, and nitrate in the study area.

Seasonality has indicated a clear impact on both selected parameters during study during wet period of Monsoon increased freshwater surface runoff in natural streams caused significant dilution and consequently reduced concentrations of BOD and COD were observed for all locations. While in contrary, during non‐ monsoon periods, the corresponding values were much higher for respective catchments. Similarly, the other pollution parameters were also analyzed in context of seasonality (Table 6). A close insight of both tables revealed that generally pH increased with rains (monsoon) mainly because runoff waters brought large quantities of wastes, while phosphorus and nitrate increased at some catchments during monsoon due to increased transport of nutrients with runoff waters. EC, on the other hand, decreased during the monsoon period due to dilution impact. To trace seasonality, further analysis was carried out and outcome of BOD and COD is shown in Figure 7. Seasonality has indicated a clear impact on both selected parameters during study during wet period of Monsoon increased freshwater surface runoff in natural streams caused significant dilution and consequently reduced concentrations of BOD and COD were observed for all locations. While in contrary, during non-monsoon periods, the corresponding values were much higher for respective catchments. Similarly, the other pollution parameters were also analyzed in context of seasonality (Table 6). A close insight of both tables revealed that generally pH increased with rains (monsoon) mainly because runoff waters brought large quantities of wastes, while phosphorus and nitrate increased at some catchments during monsoon due to increased transport of nutrients with runoff water. EC, on the other hand, decreased during the monsoon period due to dilution impact.

To trace seasonality, further analysis was carried out and outcome of BOD and COD is shown in Figure 7.

**9**

due to dilution impact.

To trace seasonality, further analysis was carried out and outcome of BOD and COD is shown in Figure 7. Seasonality has indicated a clear impact on both selected parameters during study during wet period of Monsoon increased freshwater surface runoff in natural streams caused significant dilution and consequently reduced concentrations of BOD and COD were observed for all locations. While in contrary, during non‐ monsoon periods, the corresponding values were much higher for respective catchments. Similarly, the other pollution parameters were also analyzed in context of seasonality (Table 6). A close insight of both tables

quantities of wastes, while phosphorus and nitrate increased at some catchments during monsoon due to increased transport of nutrients with runoff waters. EC, on the other hand, decreased during the monsoon period

to September 2011 had caused a lot of surface runoff that resulted in lowering of the pollution levels, nitrate and

Figure 5. Monthly rainfall pattern during study period.

nitrite increased in amount due to the washing out of human, poultry, and animal wastes.

**9 Figure 7.** Spatial variability of BOD and COD during monsoon and non-monsoon periods.

Figure 6. Temporal behavior of BOD, COD, TP, nitrite, and nitrate in the study area.


**Table 6.** Impact of seasonality on EC, TP, nitrate, and nitrite.

Statistical analysis of One-Way ANOVA technique was employed to determine significance of seasonality for various parameters. BOD indicated higher values of P (>0.1) and coefficient of variance (CV=105.3) for temporal scale and lowest values (P<0.05 & CV=73.2) for spatial scale exhibiting more variability with space than time. Similar trends were also found for COD and other major parameters. However, pH varied both spatially and temporally while Nitrites were neither temporally not spatially varied.

## **4.4. Water quality response to land use change scenarios**

There have been occurred extensive land use changes in the watershed during the last two decades resulting from deforestation and high growth in the urbanization [14]. The responses of sediment yield and water quality parameters, e.g., soluble N and P and nitrate contribution to reach, to changes in the land use were studied. The land use/land cover extent estimated in Rawal watershed during base year and under various scenarios is shown in Table 7. These scenarios are intended to be prospective and informative rather than projective or prescriptive of the future [36]. Scenario-1 is related to deforestation case in which all the scrub forest is assumed to be converted into rangeland (the rangeland increases to 75.5%). The natural forests in the country have been subjected to deforestation for growing agricultural crops, grazing domestic animals, and obtaining fuel wood and timber for the last many years [37]. The extensive grazing and cutting of wood have deformed the plants into bushes [21]. Scenario-2 represents the case of increase in agricultural development and growth in cropping activities. All the rangeland of base year is assumed to be converted into agriculture land (the agriculture land increases to 44.1%) in this scenario. Non-point sources particularly from agriculture are generally the major causes of nutrient pollution [38]. Scenario-3 is related to case of growth in urbanization under which all the rangeland of base year is assumed to be converted into builtup land, i.e., it increases to 45.6% in the watershed.

In scenario-1, the surface runoff has shown an average increase of about 0.9%, while sediment yield increases by about 26% from that of the base year 2010. The organic N and P exhibit more or less same positive change of about 23% in this scenario. The contribution of nitrate to stream flow increases slightly (about 1%) due to degradation of the scrub forest.

**9**

**Non-**

catchment 1,410 1,793 1.7 2.25 10.5 6.59 4.69 0.39

catchment 1,226 1,468 2.71 2.39 4.75 5.46 0.6 0.05

Statistical analysis of One-Way ANOVA technique was employed to determine significance of seasonality for various parameters. BOD indicated higher values of P (>0.1) and coefficient of variance (CV=105.3) for temporal scale and lowest values (P<0.05 & CV=73.2) for spatial scale exhibiting more variability with space than time. Similar trends were also found for COD and other major parameters. However, pH varied both spatially and temporally while Nitrites

There have been occurred extensive land use changes in the watershed during the last two decades resulting from deforestation and high growth in the urbanization [14]. The responses of sediment yield and water quality parameters, e.g., soluble N and P and nitrate contribution

**EC (µScm-1) TP (ppm) Nitrate (ppm) Nitrite (ppm)**

**Non-**

**monsoon Monsoon**

**Nonmonsoon**

**monsoon Monsoon**

762 926 1.1 1.61 3.5 3.6 0.03 0.11

1,303 1,343 3.25 2.6 5 8.73 0.06 0.08

580 595 0.75 0.25 4.1 2.33 0.11 0.82

**Figure 7.** Spatial variability of BOD and COD during monsoon and non-monsoon periods.

**Non-**

**Table 6.** Impact of seasonality on EC, TP, nitrate, and nitrite.

were neither temporally not spatially varied.

**4.4. Water quality response to land use change scenarios**

**monsoon Monsoon**

To trace seasonality, further analysis was carried out and outcome of BOD and COD is shown in Figure 7. Seasonality has indicated a clear impact on both selected parameters during study during wet period of Monsoon increased freshwater surface runoff in natural streams caused significant dilution and consequently reduced concentrations of BOD and COD were observed for all locations. While in contrary, during non‐ monsoon periods, the corresponding values were much higher for respective catchments. Similarly, the other pollution parameters were also analyzed in context of seasonality (Table 6). A close insight of both tables revealed that generally pH increased with rains (monsoon) mainly because runoff waters brought large quantities of wastes, while phosphorus and nitrate increased at some catchments during monsoon due to increased transport of nutrients with runoff waters. EC, on the other hand, decreased during the monsoon period

to September 2011 had caused a lot of surface runoff that resulted in lowering of the pollution levels, nitrate and

Figure 5. Monthly rainfall pattern during study period.

Figure 6. Temporal behavior of BOD, COD, TP, nitrite, and nitrate in the study area.

due to dilution impact.

192 Wastewater Treatment Engineering

**Location**

Shahdara catchment (before bridge)

Col. Amanullah road catchment

Hathala

Kiani road

Shahdara catchment (after bridge) **Monsoon**

nitrite increased in amount due to the washing out of human, poultry, and animal wastes.

In scenario-2, the surface runoff indicates an increase ranging between 0–10.1%, while sediment yield increases on an average by about 21%. The organic N exhibits an average decrease of about 1.9%, while organic P increases by 3.6% due to growth in the agriculture developments. The contribution of nitrate to stream flow increases on an average by 2.4% in the watershed (Table 8).


**Table 7.** Percentage extent of land use/land cover in base year and under various land use scenarios.

The surface runoff has shown an increase of about 3.1% in scenario-3, likely due to expansion in the imperviousness. The upper sub-basins of the watershed indicate an increase in the surface runoff under scenarios -2 and -3, the runoff being higher in the later scenario due to urban development (Figure 8). There is a minor decrease in the sediment yield (about 4.1%) in scenario-3 that may be attributed to the decrease in the rangeland, e.g., grass/shrubs that is replaced by the built-up land. The increase in the sediment yield is prominent under scenarios -1 and -2 (the cases of deforestation and agriculture development) particularly in the upper sub-basins (Figure 9). In scenario-3, the contribution of nitrate to stream flows shows a slight increase from that of scenario-2, overall presenting an identical picture of distribution in different sub-basins of the watershed under these two scenarios (Figure 10).


SURQ = Surface runoff; SYLD = Sediment yield; ORGN = Organic-Nitrogen; ORGP = Organic Phosphorus; and NSURQ = Nitrate contribution to stream flow

**Table 8.** Percentage change in the water quality parameters from that of base year.

**Figure 8.** Surface runoff under various scenarios of land use change.

The changes in various parameters in the watershed under three scenarios are shown in Figures 8–12. The organic N and P indicate an average decrease of about 4% likely due to growth in urbanization in scenario-3. The results of organic N are similar to scenario-2 but differ from scenario-1 that indicates a positive change in the upper sub-basins of the watershed (Figure 11). The changes in organic P are diverse in various sub-basins under all three scenarios, being less significant under scenario-3 due to high growth in the urbanization (Figure 12).

**Figure 9.** Sediment yield under various scenarios of land use change.

in scenario-3 that may be attributed to the decrease in the rangeland, e.g., grass/shrubs that is replaced by the built-up land. The increase in the sediment yield is prominent under scenarios -1 and -2 (the cases of deforestation and agriculture development) particularly in the upper sub-basins (Figure 9). In scenario-3, the contribution of nitrate to stream flows shows a slight increase from that of scenario-2, overall presenting an identical picture of distribution in

**Scenario Parameter SURQ SYLD NSURQ ORGN ORGP**

Max 4.311 165.759 5.247 129.144 128.692 Min 0.000 0.000 0.000 0.000 0.000 Average 0.869 26.337 1.045 23.422 23.167

Max 10.086 112.104 11.485 0.000 20.659 Min 0.000 0.000 0.000 -16.218 0.000 Average 2.128 20.994 2.407 -1.919 3.609

Max 14.375 0.000 12.509 0.000 0.000 Min 0.000 -30.002 0.000 -27.725 -27.057 Average 3.111 -4.120 2.589 -4.322 -4.148

SURQ = Surface runoff; SYLD = Sediment yield; ORGN = Organic-Nitrogen; ORGP = Organic Phosphorus; and NSURQ

**Table 8.** Percentage change in the water quality parameters from that of base year.

**Figure 8.** Surface runoff under various scenarios of land use change.

different sub-basins of the watershed under these two scenarios (Figure 10).

1

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2

3

= Nitrate contribution to stream flow

**Figure 10.** Contribution of nitrate to reach in different sub-basins of the watershed.

**Figure 11.** Organic nitrate generated under various scenarios.

**Figure 12.** Organic phosphorous generated in different sub-basins under three scenarios.
