Welcome to the environmental science blog of the Whanganui City College Science department
Grey water - Should we be recycling our grey water in Whanganui?
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A 2007 Kapiti Coast study found that of all the water consumed in the home , 50-60% was used for washing in the laundry and bathroom. This equates to 106,000 litres of water per year in a typical home. Recycling grey water for garden irrigation could reduce both the demands for mains water and waste water treatment. Grey water is the name given to the waste water that we generate when we bathe, shower or do the laundry.This is very different from black water or sewage that flows from our toilets. For a time all waste water in Whanganui was discharged directly into the Awa. Now, after separation of the storm water, the waste water generated in the city is processed through the Airport Road waste treatment plant (or soon will be again) and discharged into the ocean, 1.8km offshore
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One of the things that struck us as a learning group was why do we mix our toilet waste with our bath water and increase the amount of black waste water that has to be processed? Grey water might not be the highest quality water but what if it can be cleaned enough to use it again for other purposes like watering gardens or even recycling it to flush the toilets? This is what our Y10 STEM (Science, Technology, Engineering and Mathematics) students will be investigating over the course of 2018-19.
The current policy of the Whanganui District Council is 'if there is a reticulated sewer system for the property to connect to, they are required to connect to it and are not permitted to treat grey water on site'. This effectively rules out grey water systems within the city boundaries but not outside of this boundary. However, the times they are a changing, to borrow a line from Bob Dylan and we will be looking at how well this water can be cleaned up so that it might be possible to recycle it at home.
Summer time Rotokawau-Virginia lake, viewed from the northern edge. The southern boardwalk where water sampling took place is to the top right of the lake. Whanganui City College Science department completed a year long campaign to monitor the chemical and microbial content of the surface waters at Rotokawau-Virginia lake in September 2019. Getting out of school during the day is always difficult for a teacher and even more so accompanied by a student or two but amazingly Rotokawau-Virginia lake was visited every week, bar one, for an entire year! The purpose of this project was to try and better understand the processes that occur in a eutrophic lake. The Science programme at Whanganui City College is place-based and this means students learn about science in their own back yard. No one has spent this long studying our iconic lake so feel free to peruse the data and our observations, and understand that every one of us is capable of making science. I
The trees and shrubs three months after the experiment (From left) 4. Wharangi, 1. Kohekohe, 3. Five finger, 2. Kokomuka There was no discernible difference in the growth rates of the trees and shrubs under any of the watering conditions used in the experiment except for Kohekohe whose growth rate remained static for all water types. This probably says more about the Kohekohe specimens used or the unsuitability of the growing conditions rather than the effect of the watering.
First collect your water sample Google maps Rotokawau / Virginia lake was accessed on its southern end adjacent to the Great North Road. Here it was possible to submerge a stoppered one litre glass bottle 300mm below the surface in water at least one metre deep in accordance with sampling protocols. This was far enough away from the duck feeding areas for sampling not to be directly impeded by faecal contamination. We started testing on 20th September, 2018 and this has been repeated on a weekly basis at roughly the same time of the day, ever since. It is our stated aim to monitor Rotokawau / Virginia lake for a whole year. The water samples are tested on site and back in the school laboratory. A Vernier Logger Pro data logger is used as an interface to run an assortment of ion selective electrodes and probes and we also have a Thermofisher pH probe and conductivity meter. The full set of measurements made each week at Rotokawau / Virginia lake is as foll
A 2007 Kapiti Coast study found that of all the water consumed in the home , 50-60% was used for washing in the laundry and bathroom. This equates to 106,000 litres of water per year in a typical home. Recycling grey water for garden irrigation could reduce both the demands for mains water and waste water treatment. Grey water is the name given to the waste water that we generate when we bathe, shower or do the laundry. This is very different from black water or sewage that flows from our toilets. For a time all waste water in Whanganui was discharged directly into the Awa. Now, after separation of the storm water, the waste water generated in the city is processed through the Airport Road waste treatment plant (or soon will be again) and discharged into the ocean, 1.8km offshore
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