The study was conducted on grass (Lolium perenne) grown on fine sand in pots to evaluate the effect of greywater reuse on total dry biomass of grass during 4 months. The experiment has been designed as full factorial with total water load: 15, 25, 35 and 45 mm·week-1. Three categories of irrigation water (tap water, treated greywater, raw greywater) were tested in conditional combination with two levels for each category that is the low and high level at 5 and 15 mm·week-1, respectively. The COD, BOD5, total nitrogen, total phosphorus is 247 ± 33 mg·dm-3, 81 ± 12 mg·dm-3, 7.2 ± 0.9 mg·dm-3, 4.7 ± 0.7 mg·dm-3 of raw greywater and 81 ± 12 mg·dm-3, 23 ± 6 mg·dm-3, 4.8 ± 0.9 mg·dm-3, 2 ± 0.2 mg·dm-3 of treated greywater, respectively. The results showed that the dry biomass yields increase when increasing total irrigation water dose from 15 to 45 mm·week-1. The dry biomass yields at 5 mm·week-1 share of tap water, treated greywater, or raw greywater in total irrigation water doses 15-45 mm·week-1 were equal to 40,5 ± 7,5, 39,1 ± 7,3, 42,8 ± 6,0 mg d.m. and at 15 mm·week-1 partial dose: 52,6 ± 7,8, 54,0 ± 7,5, 50,3 ± 9,2 mg d.m. per pot, respectively. The increase in dry biomass yield of grass irrigated with treated greywater (partial dose from 5 to 15 mm·week-1) was higher and more significant (p = 0.13, 0.06, 0.37) than in the two other cases. The study concludes that treated greywater, raw greywater can be a partial or complete replacement for tap water without compromising ryegrass biomass yield.
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