Wastewater Treatment

Chapter 5

Abstract

Başak Kiliç Taşeli

warming negatively.

1. Introduction

another unit.

83

Sustainability Assessment of

Wastewater Treatment Plants

It is thought that this chapter will make a significant contribution to the literature or at least will fill the space on the wastewater treatment plant's effect on climate change. It demonstrates the potential climate change impact of a sequential batch reactor (SBR) and constructed wetland on treating domestic wastewater by giving methods for calculation of their greenhouse gas emissions in terms of N2O and CH4. Are wastewater treatment plants sustainable? What aspects determine sustainability? Do tertiary wastewater treatment plants and constructed wetlands (CWs) have less global warming potential (CO2 emissions) and less energy use than conventional treatment? In accordance with the literature, greenhouse gas calculations of this study showed that CWs and SBR WWTPs do not contribute to global

Keywords: wastewater treatment, sequential batch reactor, greenhouse gas,

Wastewater treatment plants are generally capable of reaching hygienic and environmental standards; however, these were not designed for zero discharge principle in which nutrients, organic matter, and water are recycled and nutrient, organic and water cycles are closed. Are wastewater treatment plants (WWTPs) sustainable? What aspects determine sustainability? Do tertiary wastewater treatment plants and constructed wetlands (CWs) have less global warming potential (CO2 emissions) and less energy use than conventional treatment? Since sequential batch reactor (SBR) system sequentially removes carbon, nitrogen, and phosphorous in a single reactor by maintaining anoxic and aerobic stages, it recently has attracted a great deal of interest. High nitrogen and phosphorus removal are achieved by a series of steps, namely, fill, react, settle, draw, and idle steps, as shown in Figure 1. Denitrification occurs at the beginning of the fill step taking usually 25% of the total cycling time where raw wastewater is added to the reactor. The step taking up 35% of the total cycle time is called react step where the reactions were finalized. The main purpose of the third step (settle) is to allow solid separation and provide a supernatant ready to be discharged as effluent. The purpose of the fourth step (draw step) ranging from 5 to 30% of the total cycle time is to remove clarified treated water from the reactor. The purpose of last step, "idle," is to provide time for one reactor to complete its fill cycle before switching to

constructed wetlands, methane, nitrous oxide, sustainability
