The Effect of Seasonal Variation on the Treatment Efficiency of DEWATS: A Case Study of Wazir Bagh Peshawar

Abstract

Seasonal variation significantly influences the performance of anaerobic wastewater treatment processes. Higher temperatures, typically observed during the summer months, enhance bacterial activity, thereby improving the breakdown of organic matter in wastewater. This case study, conducted at the DEWATS facility in Wazir Bagh, Peshawar, demonstrates a clear relationship between seasonal temperature changes and treatment efficiency. The findings indicate that treatment efficiency was notably higher during the summer, while a decrease in performance was observed during the winter months due to lower temperatures. Specifically, the average BOD removal efficiency was recorded at 77% in winter and 74% in summer. While temperature is a key factor, other variables such as organic loading rate and hydraulic loading rate also contribute to seasonal performance variations. This study highlights the need to consider multiple operational and environmental factors when assessing and optimizing DEWATS efficiency under varying climatic conditions.

Introduction

Decentralized Wastewater Treatment Systems (DEWATS) offer a low-maintenance, sustainable solution for treating domestic and small-scale industrial wastewater, especially in developing areas. However, their efficiency is sensitive to seasonal environmental variations, particularly temperature, which affects the microbial activity central to anaerobic digestion.

Study Focus:

The research analyzes how seasonal temperature fluctuations impact the Biological Oxygen Demand (BOD) removal efficiency of a DEWATS facility in Wazir Bagh, Peshawar over a one-year period (covering both summer and winter seasons).

Methodology:

• Sample Collection: Regular wastewater samples were collected from the system’s influent and effluent throughout the year.

• Parameters Measured: Focused on BOD reduction, using APHA standard methods.

• Analysis: Seasonal trends were identified, and the influence of other factors like Organic Loading Rate (OLR) and Hydraulic Loading Rate (HLR) was also evaluated.

Key Findings:

A. BOD Removal Efficiency

• Winter: 77% average BOD removal

• Summer: 74% average BOD removal
  → Despite higher microbial activity in summer, increased organic loading may lead to reduced efficiency if unmanaged.

B. Seasonal Influences

• Temperature is a major factor, but not the sole determinant of performance.

• System performance can remain stable in cold conditions if microbial communities are acclimated and loading is consistent.

• Variations in flow rates (from household water use or rainfall) also affect outcomes.

C. Design & Operational Implications

• DEWATS are generally robust across seasons but require adaptive management:

  • Monitor loading rates

  • Adjust operations seasonally

  • Use design features like thermal insulation for cold climates

Conclusion

This study evaluated the effect of seasonal variation on the treatment efficiency of a DEWATS facility located in Wazir Bagh, Peshawar. By monitoring key parameters such as BOD throughout the year, it was observed that the system maintained relatively stable performance across both summer and winter seasons, with average BOD removal efficiencies of 74% and 77%, respectively. Although microbial activity is typically enhanced at higher temperatures, the results indicate that treatment efficiency can slightly decline during summer months due to possible fluctuations in hydraulic and organic loading rates. Temperature, while a critical factor, is not the sole determinant of treatment efficiency. Operational factors such as flow rate, organic load, and retention time also contribute to seasonal performance variations. These findings highlight the resilience of DEWATS in coping with environmental changes, as well as the importance of continuous monitoring and adaptive operational practices. Overall, the study confirms that DEWATS can function effectively in regions with distinct seasonal climates, provided that appropriate design considerations and management strategies are in place. The insights gained from this research can inform the development and optimization of decentralized wastewater treatment systems in similar urban and peri-urban settings.

References

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Copyright

Copyright © 2025 Moheez Latif, Fayaz Ahmed Khan, Afed Ullah Khan. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.