Water and Nutrient Recovery for Cucumber Hydroponic Cultivation in Simultaneous Biological Treatment of Urine and Grey Water

Abstract

Water and nutrient deficiencies in soil are becoming a serious threat to crop production. Therefore, usable water and nutrient recovery from wastewater, such as urine and grey water, should be considered. In this work, we showed the possibility of using grey water and urine after processing in an aerobic reactor with activated sludge in which the nitrification process takes place. The resulting liquid (nitrified urine and grey water, NUG) contains three potential factors that can adversely affect plant growth in a hydroponic system: anionic surfactants, nutrient deficits, and salinity. After dilution and supplementation with small amounts of macro- and micro-elements, NUG was suitable for cucumber cultivation. Plant growth on this modified medium (enriched nitrified urine and grey water, NUGE) was similar to that of plants cultivated on Hoagland solution (HS) and reference commercial fertilizer (RCF). The modified medium (NUGE) contained a significant amount of sodium (Na) ions. Therefore, typical effects of salt stress were observed in cucumber plants, including reduced chlorophyll levels, slightly weaker photosynthesis parameters, increased H2O2 levels, lipid peroxidation, ascorbate peroxidase (APX) activity, and proline content in the leaves. In addition, reduced protein levels were observed in plants treated with recycled medium. At the same time, lower nitrate content in tissues was found, which may have resulted from their intensive use by nitrate reductase (NR), the activity of which significantly increased. Although cucumber is a glycophyte, it grew very well in this recycled medium. Interestingly, salt stress and possibly anionic surfactants promoted flower formation, which in turn could positively affect plant yield.

Replacing Mineral Fertilizer with Nitrified Human Urine in Hydroponic Lettuce (Lactuca sativa L.) Production

“…Plant experiments have been conducted in soil with unprocessed human urine [15][16][17], with nitrified synthetic urine [18], and in hydroponic systems with nitrified synthetic urine [19], as well as with nitrified human urine to grow lettuce [20,21], tomato plants [22], and cucumber plants [23]. Human urine, also after nitrification, contains concentrations of sodium and chloride higher than those usually found in nutrient solutions (e.g., 0.3 mol Na + and 0.4 mol Cl − per mol dissolved nitrogen) [9].…”

Jasmonic Acid Effect on Cucumis sativus L. Growth Is Related to Inhibition of Plasma Membrane Proton Pump and the Uptake and Assimilation of Nitrates

“…The level of lipid peroxidation was measured according to Kabała et al [ 26 ] with some modifications as described by Wdowikowska et al [ 27 ]. In the method, the concentration of thiobarbituric acid reactive substances (TBARS), formed in acidic pH during incubation at 95 °C, was determined.…”

“…After incubation of the reaction mixture in darkness at room temperature for 60 min, the absorbance of triiodide (I 3 − ), the product of potassium iodide (KI) oxidation, was measured at 390 nm. The level of lipid peroxidation was measured according to Kabała et al [26] with some modifications as described by Wdowikowska et al [27]. In the method, the concentration of thiobarbituric acid reactive substances (TBARS), formed in acidic pH during incubation at 95 • C, was determined.…”

Modelling Possible Household Uses of Grey Water in Poland using Property Fitting Analysis

“…The simplest way to save water is to reduce water abstraction [22]. Optimising the use of limited water resources is being addressed by new technologies, including grey and rainwater recycling [23].…”