Combined ultrasound-ozone treatment for reutilization of primary effluent—a preliminary study

Abstract

The present work is a preliminary study on the potential of low-frequency ultrasound irradiation coupled with O 3 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-O 3 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 pretreatment, 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.

A simple system for ozone application in domestic sewage for agricultural reuse

“…Nitrogen showed a trend similar to that of carbon in ozonated sewage samples, i.e., a slight variation and no significant difference between doses. Rossi et al (2021) also observed a similar result when studying the effect of ozone and ultrasound on the agricultural reuse of primary effluents. On the other hand, these authors reported that a slight increase in TN would probably be related to a release of nitrogen material from particulate organic matter.…”

Effect of Hydraulic Retention Time on the Performance of a Compact Moving Bed Biofilm Reactor for Effluent Polishing of Treated Sewage

“…Elwakeel et al [6] pointed out that magnetic thiourea-formaldehyde polymer loaded with silver ion provides a promising disinfectant activity against microbial pathogens in the water and wastewater samples with high magnetic-separation ability. Additionally, since there are many modern technologies available, appropriate polishing treatment for water reuse can be selected based on a "fit-for -purpose" approach [7].…”

Efficiency of Natural Clay Mineral Adsorbent Filtration Systems in Wastewater Treatment for Potential Irrigation Purposes

“…There are numerous chemical techniques which have been employed in wastewater treatment, such as chemical coagulation [1], Fenton reaction [2], ion exchange [3], precipitation [4], combined ultrasound-ozone [5], ultra-filtration [6], electrochemical techniques [7], adsorption [8][9][10], and packed columns in water treatment applications [11,12] to eliminate trace and heavy elements, micropollutants and other hazardous materials (i.e., biochemical oxygen demand (BOD), chemical oxygen demand (COD), paint, phenol, oil and grease, total suspended solids (TSS), and coliform bacteria) from industrial, municipal and drainage wastewaters, and aqueous media [1]. Among all of the above-mentioned techniques, adsorption in clay minerals is viewed as an especially powerful procedure, particularly regarding the use of low-cost, biodegradable, and environmentally-friendly materials for the removal of pollutants from wastewaters and aqueous solutions [13].…”