Hello folks!
Unfortunately I did not submit my application for this challenge before the deadline, but I would like anyway to share a project for greywater recycling. In the last few years, climatic changes have severely affected my region, with long dry periods followed by violent storms. These events increased my awareness about the use (and, too many times, misuse) of water in my everyday life. Since I already have rainwater tanks, I tried to think about new ways to save water, and my attention has fallen on greywater and its possible reuse for gardening.
I hope this blogs series may inspire awareness in as many people as possible about what a precious and scarce resource water is.
Posts in this project
AquaFlow - Blog #1 - Introduction
AquaFlow - Blog #2 - The coarse filter
AquaFlow - Blog #3 - The sedimentation tank
AquaFlow - Blog #4 - The reed bed
AquaFlow - Blog #5 - The storage tank
AquaFlow - Blog #6 - Conclusions
1. What is greywater
Greywater is wastewater from non-toilet plumbing systems such as hand basins, washing machines, showers and baths. When handled properly, greywater can be safely reused for the garden.
Greywater is an abundant resource. According to some studies, the average household use of water is partitioned as follow:
- bathroom – 50 per cent
- laundry – 22 per cent
- garden – 19 per cent
- kitchen – 8 per cent.
As you can see, showers use the most water, followed by washing machines.
The majority still use clean drinking water for most household uses. Some of this precious resource could be conserved by recycling water.
1.1 Benefits of using greywater for gardening
Saving water is just one of the advantages of recycling greywater. Other benefits are
- Improves plant growth. Greywater can contain nutrients that can help plants to grow better.
- Reduces pollution. Greywater that is reused for gardening does not have to be treated to the same standards as wastewater that is discharged into the environment.
- Reduces workload on the water treatment plants
1.2 Risks correlated to greywater
On the other hand, there are some health risks that must be taken into account while designing a grey water treatment system.
First of all, it’s important to focus on the behaviors that may pose risks to your health.
- Never use water that has come in contact with the toilet or any other toileting fixture such as a bidet or urinal.
- Don’t use water that has been used to wash soiled nappies – this is also considered blackwater.
- Don’t reuse the water when you wash domestic pets, because of the high level of bacterial contamination.
- Don’t use greywater from the kitchen sink or dishwasher, as this can be contaminated with grease, bacteria and chemicals.
Also, it’s important to note that greywater include the following contaminants:
- Salts
- Food materials
- Household detergents, soaps and chemicals
- Bacteria and other disease-causing microbes.
1.3 How can greywater be used for gardening?
Because the contaminants in greywater can not be completely eliminated by a domestic treatment system, some precautions should be followed when greywater is used for gardening.
- Use greywater to water plants that are not edible. This includes trees, shrubs, flowers, and ornamental plants.
- Apply greywater to the soil around the plants, not directly to the leaves. This will help to prevent the spread of any contaminants that may be present in the greywater.
- Do not use greywater on plants that are sensitive to salts. These include citrus fruits, avocados, and tomatoes.
- Avoid using greywater that contains hair, grease, or other debris. Beside clogging irrigation systems, they also damage plants. Use a coarse filter to reduce the amounts of solids in your greywater to prevent your plants from suffering because of clogged soil
- Store only for a short time – don’t store untreated greywater for any longer than 24 hours, as microbes will thrive. Your surge tank shouldn’t exceed 80 litres. Make sure you have an overflow drain connected to your surge tank that directs excess greywater straight to the sewer. You may want to get advice from a plumber on installing a settling tank to capture grease.
- Regularly water your garden with fresh water to help prevent the build-up of salts in your soil.
2. Greywater treatment system
There are literally millions of resources on the web about how to build a greywater treatment system, but in general the rules to follow are
- A coarse filter
- A first sedimentation tank
- A reed bed
- A storage tank
I tried to follow these rules and create a small experimental setup for the treatment system. Here is a diagram of the system I am going to build
