Prepared by Stephen McIllwaine, 2003
2.5 Test Scheme at JUST
The Jordan University of Science and Technology (JUST) has been engaged in a project to use the graywater from one of the accommodation blocks housing 69 female students. It is estimated that 80% of the wastewater from the accommodation block - amounting to an average of about 2 cubic meters per day - is graywater. This includes the kitchen sinks. The graywater is collected at an external manhole and taken to 2 underground storage tanks from where it is pumped to the irrigation area. Figure 4 shows the irrigated planted area with the accommodation block in the background.
This work has been written up in Qaqish, LM, ‘Effect of Grey Water Irrigation on Soils and Crops', MSc Thesis, Jordan University of Science and Technology, May 2003. One interesting feature of this project was the inclusion of a reed-bed treatment system to treat a component of the graywater. A sloped enclosure was established, consisting of an area of healthy soil placed over an impermeable fabric. Reeds were cultivated in this enclosed area of soil. Untreated graywater was released into the upstream end of this zone and was captured downstream. The estimated retention time for the graywater was 4 days. The ‘treated' graywater was stored in a third tank for later reuse.
A compartmentalized irrigation area was developed, containing fava beans, spinach and carrots in controlled areas. A component of the area was irrigated with the untreated graywater. A second area was irrigated with the treated graywater, while a third was irrigated with mains water. The scheme was irrigated over a period of 5 months and tests were completed on the water, soil and the plants irrigated.
Water, soil and plant matter were extensively tested throughout the project for a number of parameters, and the results are presented and discussed extensively. The main conclusions are that the reed bed was successful in reducing the amount of BOD, COD, turbidity, nitrates and bacterial content. The results indicated a high concentration of heavy metals in the soil although this is considered to be due to impurities in the storage and distribution system, and not arising from the graywater itself. However, if the graywater were to be reused for the irrigation of ornamental plants, the presence of heavy metals in the graywater would give no cause for concern.
2.6 Urban Household Laundry Water
Wastewater from the laundry is one source of graywater which is anecdotally regarded as potentially suitable for reuse in Jordan. In order to provide more information about the constituents of laundry water in Jordan, tests were carried out on an urban household in Amman. The wastewater from one complete laundry cycle from an automatic washing machine on wash day was sampled and tested. Unfortunately, the tests were not able to be carried out directly after the wash had been completed, and the wash water was stored for 18 hours before the first analysis was carried out. The second results were taken from the stored laundry water sample, after 4 weeks of storage in a sealed barrel, standing outside the house. The results are as follows;
|Parameter||After 18 hours||After 4 weeks||
|pH||7.4||7.5||6.0 - 9.0|
|Chloride, Cl (mg/l)||213||231||<350|
|Sodium, Na (mg/l)||268||89||<230|
|Faecal Coliforms (MPN/100 ml)||16 X 10^6||16 X 10^5||-|
Table 3: Results of water quality tests conducted on the laundry water of an urban house
An expected reduction in organic content (as indicated by the BOD) is seen, with the BOD decreasing by about 50 % during the 4 weeks time period between tests. This arises from the breakdown of the organic material by the indigenous bacteria in the graywater. The coliform levels are high, indicating favourable conditions for their growth, (although the bacterial levels directly following the laundry cycle would have been much lower, following the oxidation effects of the detergent and the hot water). The bacterial levels fell by a factor of 10 during the time period, possibly indicating a reduction in the intensity of the anoxic digestion process. As expected, the results show little change for the ionic concentrations (boron and chloride), although the increase in ionic sodium content is unexplained.
The relevant guideline parameters for irrigation of fruit and forestry trees, given in Jordanian Standard 893 (for irrigation by treated wastewater) have also been presented. It is interesting to note that there is no requirement for coliform levels to be below certain limits. Provided there is no contact between people and graywater, and the graywater is not used to irrigate areas used by humans or animals (eg grass areas), the presence of coliforms in the graywater does not constitute a problem to the plants. Bacteria die quickly after coming into contact with healthy soil. All other parameters are within the range recommended by the code, with the exception of Boron and Sodium. These substances are important constituents of laundry detergent and are present in the laundry graywater. It can be seen here that despite the inclusion of the laundry rinse cycle in the test water (and the subsequent dilution effect), the concentration of these substances exceeds the recommendation in the code. Boron and Sodium are both substances which will cause damage to plants once their concentration rises above certain levels. If this laundry water were to be used consistently in graywater applications, it would need to be used in conjunction with other graywater, which had a diluting effect on these substances. In addition, care in plant selection would also be required, as some plants are more tolerant of sodium and boron than others. Further information is given elsewhere on the CSBE Graywater website.
Further research is needed to determine both the average content of laundry water in urban and rural contexts, and to determine the long term effect of high concentrations of boron and sodium on certain plants.