Environmental impacts of greywater use for irrigation on home gardens
This study focuses on the feasibility and environmental impacts of using raw domestic greywater from laundry and bathroom after only primary treatment, e.g. coarse filtration for irrigating lawns and gardens. The use of greywater for landscape irrigation requires careful management, especially in...
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| 格式: | Thesis |
| 语言: | English |
| 出版: |
2011
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| 主题: | |
| 在线阅读: | http://eprints.uthm.edu.my/3071/1/24p%20RADIN%20MAYA%20SAPHIRA%20RADIN%20MOHAMED.pdf |
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| 总结: | This study focuses on the feasibility and environmental impacts of using raw
domestic greywater from laundry and bathroom after only primary treatment, e.g.
coarse filtration for irrigating lawns and gardens. The use of greywater for
landscape irrigation requires careful management, especially in regions with sandy
soils and shallow groundwater levels. There is the possibility that excessive
nutrients and other contaminants will leach into surrounding water bodies. This has
.been a major concern with greywater use in ecologically sensitive environments,
such as on the Swan Coastal Plain of Perth, Western Australia. Proper
management is essential to ensure environmental risks from greywater irrigation
are avoided.
The main purpose of the first stage of the study was to develop a new zero-tension
lysimeter (ZTL) as a leachate sampler in a greywater irrigation plot. The new ZTLs
were tested to compare the quantity and quality of leachate collected with that from
the conventional pan lysimeter, in a pilot-scale study. The results indicate that the
new lysimeter designated as ZTL (NI), was effective at collecting leachate and
was suitable to install at household sites. The lysimeter ZTL (NI) design offers
significantly improved performance, was cost-effective and required limited effort to
install using an auger, which also minimizes soil disturbance. Since the lysimeter
was practical and inexpensive it was established to facilitate the monitoring of
greywater irrigation.
The second stage of the study was to monitor the use of primarily treated
greywater by using diversion system from bathrooms and laundries at four Perth
houses: two houses at the Bridgewater Lifestyle Village (BWLV), one each at
White Gum Valley and Hamilton Hill. Each house had different characteristics:
different house types, occupants, cleaning product preferences and presence, or
not, of household pets. Water use activities, soil and vegetation were monitored
and were sampled for physical and chemical characteristics. Groundwater samples
at the BWLV site were also collected. This site has 389 houses with a greywater diversion system installed in each, is located close to the Peel-Harvey estuary and
a wetland, an-d has a shallow aquifer. Monitoring results showed that the
groundwater samples were within the ANZECC guidelines. Greywater quality
showed high variability depending on water consumption by washing machines,
use of detergents and fabric softeners, as well as individual lifestyles. Land
activities such as fertilizers and pets were expected to contribute to high amounts
of nutrients in the leachate. Mulching and fertilizer used by householders in
conjunction with greywater irrigation improved the function of soil and condition of
. plants.
The third stage of the study was to determine the effects of raw laundry and
bathtub greywater irrigation on the growth of couch grass (Cynodon dactylon L.)
sod on a sandy soil in a 24-week study, from October 2009 to March 2010. In
Perth, the use of greywater is significant during these months as rainfall is at its
lowest and irrigation demand at its highest. Couch grass is a common lawn used in
Western Australia with excellent drought tolerance, water efficiency and relatively
low maintenance requirements. Three irrigation treatments were applied using a
modified aquarium tank: (i) 100% scheme water as a control (TW), (ii) untreated
full cycle laundry water (LGW), (iii) untreated bathtub water (BGW). Salts and
nutrients Na, CI, P, Ca, Mg, K, B, Zn and Al were chosen for measuring because
they are dominant constituents in greywater and have a beneficial role in turf grass
growth. Their dynamics and mass balance were assessed by measuring the
irrigation (input) and leachate (output) volumes and concentrations of element
concentration in both input and output water of the tank. Irrigation using LGW and
BGW in sand resulted significant leaching of some Mg and Al beyond the 30cm
root-zone depth. The mass balance showed an increased amount of stored Na, CI,
P and K in the soil at the end of the study. The accumulation of salts and nutrients
in the soil has resulted in the infiltration rate, K, gradually declining.
The final stage of the study was to investigate further the significant reduction of K
in the tank test. Another soil hydraulic property, capillary rise (P,), was also
measured. The soil samples were collected from greywater-irrigated plots at the
case studies and the tank test, as mentioned previously. In addition, the study examined the changes in soil properties from the use of an anionic surfactant,
linear alkylbenzene sulphonate (LAS) which is known to be the main ingredient in
detergent formulation. A commercially available surfactant-based wetting agent to
alleviate water repellency in household gardens was also considered. Irrigation
with raw laundry and bathtub greywater, application of LAS and a wetting agent
made a significant reduction on infiltration rate, K, and on PC. At the case study
sites, the changes were difficult to quantify owing to various land activities that
influenced the result.
The results of the extensive experimental on-site program indicated that the use of
primarily treated greywater is a viable option to conserve water for irrigation during
times of drought and water restrictions. The sustainable use of raw greywater
would vary with specific site conditions and householder practices. Soil and plant
quality parameters are significantly affected after continuous irrigation with
greywater. This is mainly determined by the management regime of greywater
irrigation and its composition. In addition, continuous irrigation with greywater may
lead to accumulation of salts, plant nutrients and some nutrients beyond plant
tolerance levels. Therefore, these concerns should be essential components of any
management plan for greywater irrigation. On the other hand, plant growth, soil
fertility and productivity can be enhanced with properly managed greywater
irrigation, through increasing levels of plant nutrients and soil organic matter. It is
suggested that proper management of greywater irrigation with periodic monitoring
of soil fertility and quality parameters are required to ensure successful and safe
long-term use of greywater for irrigation. The adequate assessment of any
environmental risks will require further research. |
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