Combined ultrasound-ozone treatment for reutilization of primary effluent\u2014a preliminary study

Giada Rossi,Daniele Goi,Linda K Weavers,Matia Mainardis,Eleonora Aneggi

doi:10.1007/s11356-020-10467-y

Abstract

The present work is a preliminary study on the potential of low-frequency ultrasound irradiation coupled with O3 process for the disinfection of a primary effluent from a municipal wastewater treatment plant preserving nutrient levels (in particular nitrogen and phosphorous), for its possible reuse in civil, industrial, and agricultural sectors. The treated water could be reused, after appropriate dilution, contributing to the circular economy perspective and reducing the need for both chemical fertilizer addition and freshwater supply. The effect of different specific ultrasonic energies and ozone doses was assessed on a bench-top system, composed of an ultrasonic reactor and a semi-batch ozonation vessel. The results showed that the combined US-O3 process produces a good removal efficiency regarding soluble Chemical Oxygen Demand, sCOD (ca. 60%), anionic surfactants (ca. 50%), and formaldehyde (ca. 50%), and an optimal abatement for Methylene Blue Active Substances (MBAS, > 90%). The process also reached high disinfection performances, obtaining 4 logs for E. coli and 5 log abatement for Total Coliforms. The high removal efficiency is matched by an outstanding retention of nutrients (total nitrogen and orthophosphate) highlighting a high potential value for agricultural reuse of the treated primary effluent, with possible significant saving of chemical fertilizers. It was concluded that low-frequency ultrasound pre-treatment, combined with ozonation, could be a useful process for primary effluent recovery for several purposes. Further studies are expected to be planned and executed to evaluate system scale-up feasibility.

Highlights

Fresh water scarcity has become one of the most significant environmental challenges in the twenty-first century, mainly caused by an uneven distribution of water resources throughout the world (Jasim et al 2016)
It could be noted that the primary effluent was characterized by a moderate organic charge and a good nutrient concentration (TN up to 21.13 mg N/L and orthophosphate concentration of 5.80 mg P/L), while suspended solid material and turbidity were comparable with other WWTPs in the analyzed area
The present study focused on a new circular economy approach for the water cycle with special attention to water/ nutrients re-use by reduction of the current water consumption, contributing to the challenge of raw materials depletion

Summary

Introduction

Fresh water scarcity has become one of the most significant environmental challenges in the twenty-first century, mainly caused by an uneven distribution of water resources throughout the world (Jasim et al 2016). The agricultural sector accounts for about 70% of total water usage (Jasim et al 2016). It appears unavoidable to boost for treated wastewater reuse in this sector, as an essential component of an integrated and sustainable water resources management (Farhadkhani et al 2018). In response to the increasing agricultural demand for water, coupled with water shortages, countries such as Israel, Singapore, and Australia recently adopted water reclamation programs (Savchenko et al 2019). Reclaimed water contains valuable components, in particular nutrients (nitrogen and phosphorous), potentially reducing the need for nutrient addition to the agricultural lands, with a global positive environmental and economic impact

Methods

Results

Conclusion