TRACKING OUR LIVES AND OUR IMPACT ON THE ENVIRONMENT VIA OUR WASTE

By Dr Paul Whitehead

The availability of more and more sensitive multi-component analytical techniques has raised the possibility of monitoring human (and other) activities by analysis of collective waste. A topical example is the potential detection of COVID-19 antibodies in waste as a means of early warning of an increase in cases in a locality. Other substances sought include illicit drugs and caffeine, nicotine, flame retardants and plasticisers. A more general application is illustrated by the recent work by Kadokami and colleagues who studied the levels of 484 chemicals, including 162 pharmaceuticals and personal care products (PPCPs) in daily use.

Chemicals that are used domestically and in commercial and business properties are eventually discharged to the sewerage system and reach municipal wastewater treatment plants (WWTPs). Thus, the local release of such chemicals can be determined by examining their concentrations in the inflows and outflows of WWTPs (an approach known as wastewater-based epidemiology (WBE)). They are sampled at eight waste treatment plants across Japan to obtain data on levels of these chemicals produced by various communities and any seasonal variations, to identify markers of sewage contamination and to assess the efficiencies of their removal during sewage treatment with a view of protecting the aquatic environment. The table summarises the range of materials sought and found

24-hour composite samples were collected at points before and after treatment from all eight sites four times over a year. Samples were stored cold and extracted the same day. The solid-phase extracts were washed with ultrapure water, dried by nitrogen, and eluted with methanol and dichloromethane. Mixed internal and matrix standards were added, and chemical concentrations were determined using LCQTOF-MS (quadrupole time-of-flight mass spectrometry). For 85% of the chemicals, it was found that the method detection limits were below 8 and 2 ng/L for inflow and outflow, respectively. The target compounds were identified using the mass accuracies of a precursor and product ions, their ratios and retention times. Quantification of the identified target substance used six internal standards. An ELGA PURELAB Chorus 1 provided the ultrapure water used.

87 out of the 484 daily-use chemicals sought were detected in the inputs to the WWTPs with an average total concentration of 0.1 mg/L. Pharmaceuticals made up 50% of the total. The individual substances found at the highest concentrations were the pharmaceuticals metformin, theophylline and theobromine, the sweetener sucralose, the brightening agent distyrylbiphenyl disulfonate (FB351) and the surfactant N, N-Dimethyldodecylamine N-oxide. Removal efficiencies in the WWTPs were low, at only 29% for pharmaceuticals and 20% for pesticides. Seasonal variations could be detected, with the levels of sucralose, UV-filters and insecticides higher in the summer, while ibuprofen and chlorpheniramine were higher in the winter. 22 substances were identified that could serve as markers for sewage contamination.

24-hour composite samples were collected at points before and after treatment from all eight sites

LABOTEC (PTY) LTD

JHB: (011) 315 5434 CPT: (021) 531 7660 DBN: (031) 566 4870 Fax: (011) 315 5882 sales@labotec.co.za www.labotec.co.za