As part of the recent virtual BT Young Scientist event, Caolán Ó’Riordáin from Mohill Community College, Co Leitrim, focused his project on the effect of grey water on plant growth and the environment, by comparison to that of mains water.
The transition-year student’s investigation was inspired by his concern for the worldwide increase of water shortages and droughts.
To begin his trial, Caolán collected grey water from the family washing machine.
He then planted the seeds in a number of identical containers. To ensure a broad and fair experiment, each container held different ratios of mains water to grey water.
As part of his research, Caolán sent out detailed surveys on washing machine use to gain a better insight into people’s attitude towards grey water.
As a result, he concluded that most people would consider recycling grey water if they had a better understanding of its benefits.
I can conclude that using grey water on plants is a great way of reusing water and improving sustainability
He also voiced the health concerns of participants, who worry that the chemicals in grey water would affect the edibility of plants.
After gaining more insight, Caolán could conclude that most common fertilisers have far more chemical content than grey water.
By examining each group of seeds planted, Caolán found that the seed containers with a ratio of 3:2 and 2:3 of grey water:fresh water, showed the greatest amount of plant growth and germination.
“From this investigation, I can conclude that using grey water on plants is a great way of reusing water and improving sustainability. Grey water can act as a fertiliser, as the phosphates (nutrients) in grey water improve plant growth. I would recommend getting 50:50 grey water to fresh water to get the best effect on your plant’s growth.
“Collecting the water from the washing machine only took a matter of minutes and could be tried by anyone.”
The expert’s response
Stephen Robb – tillage and crops specialist with the Irish Farmers Journal
“While rainfall is abundant in Ireland, the frequency of extreme weather events has been increasing.
“Over the past three years, we have seen periods of extreme dryness in areas of the country, leading to the need for irrigation in certain crops, namely in the horticultural industry.
“Irrigating crops accounts for a significant volume of water usage in many parts of the world.
“According to the United Nations Educational, Scientific and Cultural Organisation (UNESCO), irrigated agriculture covers 275m hectares of land or around 20% of cultivated land. This accounts for 40% of global food production.
“In the US alone, irrigating agricultural crops accounts for 80% of the nation’s water consumption.
It is imperative that greater focus be given to resource efficiency which includes the recycling of waste streams
“With further increases in population trends, the requirement for water for human consumption and hygiene as well as crop production will also increase.
“Therefore, it is imperative that greater focus be given to resource efficiency which includes the recycling of waste streams.
“Caolán’s project on reusing grey water for agricultural purposes is a great example of this.
“Grey water, which would otherwise be released into drains and sewers, could potentially turn into an important resource if it can be mobilised and is safe for use.
“As alluded to in Caolán’s survey results, respondents were concerned at the potential for crop contamination by the chemicals used in the washing process.
“While these chemicals are released into the environment, the potential impacts of residues from applying the grey water in a highly concentrated form to growing crops would need further investigation.
“Using the water in this way wasn’t intended by the product manufacturers. Perhaps a cleaning and filtration step is required to strip the chemical residues from grey water before being applied to crops.”
With a homegrown grá for all things horticultural, Evie Ní Nuanáin from Colaiste An Phiarsaigh, Co Cork, directed her project towards the garden.
Seeking to configure real-life data on the mental health benefits of horticulture, Evie generated a short and concise online survey, which she sent out to 75 organisations.
Pleasantly surprised by the interest in her survey, Evie soon received hundreds of varied and informative responses.
So many people have had to give up pastimes because of these lockdowns and I think it is really important for people to consider gardening
The end data was undisputed and unified in claiming that horticulture has a positive effect on mental health.
Out of 365 responses received, 350 reported that gardening has a positive impact on their mood.
When asked how they would feel without gardening, over 340 people claimed that they would miss the pastime immensely.
Touching on the current 5km restrictions, Evie highlighted the relevance of her survey’s data.
“So many people have had to give up pastimes because of these lockdowns and I think it is really important for people to consider gardening.
“It is good to release stress and my survey also showed that people feel at peace when gardening, which is so important at the moment.
“Although my experiment was not extremely scientific, I think it really helped to reinforce and add to figures that already exist.”
The expert’s response
Deirdre Walsh – assistant principal in the Teagasc College of Amenity Horticulture at the National Botanic Gardens
“Evie’s excellent and timely research emphasises what we in the industry have known for a long time, the positive effects of working outdoors can have on our wellbeing.
“This has never been more evident than during the pandemic. With our new-found slower pace of life, we’ve had time to reconnect with nature and appreciate our green spaces or gardens a lot more.
Students learn about the benefits and impacts horticulture has for different groups of people
“The pandemic’s impact is reflected in the number of students who applied to complete horticultural courses across all our levels in our college, far exceeding recent years.
“Many of our students choose to study horticulture because they find working outdoors in green spaces positively affects their mental health.
“Students learn about the benefits and impacts horticulture has for different groups of people. Horticulture is an excellent career choice that will not only offer you a solid career, but the peace and tranquillity of working outdoors.”