Chemical aspects of peracetic acid based wastewater disinfection

T Luukkonen,J Teeriniemi,H Prokkola,U Lassi,J Rämö

doi:10.4314/wsa.v40i1.9

Abstract

Peracetic acid (PAA) has been studied for wastewater disinfection applications for some 30 years and has been shown to be an effective disinfectant against many indicator microbes, including bacteria, viruses, and protozoa. One of the key advantages compared to, e.g., chlorine is the lack of harmful disinfection by-products. In this paper a pilot-scale study of PAA-based disinfection is presented. Indicator microbes (E. coli, total coliforms and coliphage viruses) as well as chemical parameters (pH, oxidation-reduction potential (ORP), chemical and biochemical oxygen demand (COD and BOD), and residual PAA and hydrogen peroxide) were studied. The main aim of this investigation was to study how these selected chemical parameters change during PAA treatment. Based on the results, disinfection was efficient at C·t values of 15 to 30 (mg·min)/l which equals to a PAA dose of 1.5 to 2 mg/l and a contact time of 10 to 15 min. In this concentration area changes in pH, COD and BOD were negligible. However, hydrogen peroxide residues may interfere with COD measurements and apparent COD can be higher than the calculated theoretical oxygen demand (ThOD). Additionally PAA or hydrogen peroxide residues interfere with the BOD test resulting in BOD values that are too low. Residual PAA and ORP were found to correlate with remaining amounts of bacteria. Keywords : tertiary wastewater disinfection, peracetic acid, total coliform, E. coli , coliphages

Highlights

Wastewater treatment has traditionally focused on the removal of solids, organic material and nutrients
Bergendahl and Stevens (2005) showed that when oxidation–reduction potential (ORP) is greater than 650 mV, it ensures bacterial inactivation against E. coli, Salmonella or Pseudomonas, which is in agreement with WHO guidelines for keeping ORP at 700 mV during the disinfection of drinking water (Goncharuk et al, 2010)
We conducted a similar test with peracetic acid (PAA) and our results (Fig. 3) showed that a linear correlation between residual PAA and total coliform bacteria (TCB) or E. coli values is slightly better than for ORP and total coliform amounts

Summary

Introduction

Wastewater treatment has traditionally focused on the removal of solids, organic material and nutrients (phosphorus and more recently nitrogen). Remaining pathogens are often thought to diminish via dilution in natural waters or to be inactivated by stress factors such as pH, temperature, salinity, nutrient availability, and oxidative stress (Rozen and Belkin, 2001). This is not always sufficient if there are activities taking place which involve the receiving water body, such as bathing, fishing or fish farming for example. Chlorine is still globally the most common disinfectant due to its low cost, the awareness of harmful by-products and the formation of chlorination-resistant bacteria strains causes wastewater plants to consider other options. Performic acid (PFA) has been proposed as a wastewater disinfectant but additional research is necessary as there are currently no published results about, e.g., by-product formation and toxicity effects (Gehr et al, 2009)

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Conclusion