Water, Sewage & Effluent May-June 2018 | Page 42

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A matter of taste

Much has been mooted around reusing toilet water , but there has been some resistance to this innovation and the question often revolves around taste : Is there a difference in taste between toilet water and tap water ? By Kim Kemp

In March 2018 , Cooperative Governance and Traditional Affairs Minister Zweli Mkhize declared the prevailing water crisis affecting multiple South African provinces a state of national disaster . As the water crisis continues , recycling wastewater was suggested as the answer to augmenting municipal water scarcity , in combination with water from desalinisation plants and groundwater , via boreholes .

The picky consumers , however , have been quick to pick up on the ‘ recycled ’ aspect , even calling the technology ‘ toilet to tap ’ — or worse . ( I ’ ll just leave that there and let the poet in you work it out .)
The truth is , it is difficult to taste the difference between fresh and recycled water , and results of a blind taste test suggest that it is unlikely .
Historically , research has centred mostly around the safety of water , with wastewater being treated using reverse osmosis . A preferred technology is called indirect potable reuse , or IDR , which reintroduces treated wastewater into groundwater supplies , where it is mixed into the drinking water system .
The research
The University of California , Riverside ( UCR ), included 143 people in a study to compare IDR-treated tap water with conventional tap water and commercially bottled water . The waters were offered in similar , unlabelled cups , making the participants ‘ blind ’ to the source of the fluid . The theory was that all three would score similarly , but interestingly , tap water was the least popular among the tasters , while recycled water and bottled water scored about the same . After tasting the water , participants ranked the samples ’ taste from one to five , then also in categories including texture , temperature , smell , and colour . Factors that influence taste perception were weighted by the researchers .
One such factor is genetic , which determines differences in taste sensitivity . This degree of sensitivity was gauged using a tried-and-true measure : paper strips coated with the chemical phenylthiocarbomide , or PTC . Those who find the strip ’ s taste bitter are considered to have elevated taste sensitivity .
Researchers also considered two personality traits that help determine water preference . These traits are referred to as ‘ openness to experience ’ and ‘ neuroticism .’ The former is gauged by how receptive people are to novel and diverse experiences , while neuroticism refers to anxiety and insecurity .
While from the outset , researchers assumed the three waters would score equally , one in fact , emerged the least preferred .
“ The groundwater-based water was not as well liked as IDR or bottled water ,” says Mary Gauvain , a professor of psychology at UC Riverside and co-author of the study . “ We think that happened because IDR and bottled water go through remarkably similar treatment processes , so they have low levels of the types of tastes people tend to dislike .”
The more nervous , anxious people in the study expressed the preference for IDR and bottled water , while also expressing more negativity about the more mineral-rich tap water . While people more open to new experiences found all three samples to be almost on a par . Another surprise was that twice as
many women were likely to prefer bottled water as men .
The researchers ’ best guess : Women register higher ‘ disgust reactions ’ than men , which means their reactions to tastes they dislike are more extreme . ( These disgust reactions will form the subject of the team ’ s next research paper .)
In its conclusion , researchers suggest that favourable comparisons between reverse osmosis and bottled water may make consumers more open to drinking recycled wastewater . u
Aside from Harmon and Gauvain , researchers in the study include Isaac Arthur , who recently completed his undergraduate studies at UC Riverside ; Drew Story , a graduate student at UC Riverside ; and Z Reisz , who received his PhD at UC Riverside and is now at Santa Barbara City College . The research was supported by an Integrative Graduate Education and Research Traineeship , or IGERT , award from the National Science Foundation .
Source : www . health24 . com : Lifestyle / Environmental-health / News / couldyou-taste-the-difference-betweentoilet-water-and-tap-water-20180403
Most people are disgusted at the thought of drinking water from waste .
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