Extended use of grey water for irrigating home gardens in an arid environment

The use of treated grey water (GW) for home gardens, peri-urban agriculture and landscaping is becoming popular in many water stressed countries such as Oman. This study aims to investigate the treatment efficacy, health and chemical concerns, cost-benefits and maintenance protocol of a GW treatment system as well as the effect of irrigation with GW on crop yield. Therefore, a decentralized homemade GW treatment system was installed in a newly constructed house in Muscat, Oman and studied over a 2-year period. The treated GW was found to be suitable for irrigation as per Omani standards. GW when mixed with kitchen effluent substituted the use of nutrient supplements for plants and did not show any harmful chemical or biological contamination. The capital cost of the system was around US $980, and the annual operating cost was US$78 with annual income and savings from the system being around US $572 indicating a payback period of nearly 2 years. It was found that the system required simple but regular maintenance particularly cleaning of the top layer of the filter. It can be concluded from this study that such a GW system should be technically, economically and environmentally feasible in Oman. Also, wider acceptance by the general public to the idea of GW reuse will help in mitigating the water shortage problem of the country to some extent

Modelling of a humidification-dehumidification greenhouse in Oman

The humidification-dehumidification (HD) greenhouse is a relatively new technology. In addition to the humidification process and cultivation normally present in greenhouses in arid countries, the HD greenhouse also integrates a dehumidification process. In these greenhouses, saline or brackish water is evaporated in the ordinary evaporative cooling pads (i.e. 1st humidifier) before passing through the main crop growing section. The air is further loaded with more moisture by passing it through a 2nd humidifier. This humidification process is then followed by a dehumidification process to condense as much water vapour as possible. The main purpose of the HD greenhouses is to find a cheap means of desalinating saline water for the sake of using the condensate for irrigation. Most of previous attempts to improve the performance of the HD greenhouses have used a trial-and-error approach. An alternative approach is to use simulation models. Due to the absence of such models, this research study aims at developing a simulation model capable of simulating the significant processes of the HD greenhouses. The developed model is an integration of three sub-models each of which simulates one element of the HD greenhouse. The simulated elements are humidifiers, cultivation area (i.e. microclimate) and dehumidifiers. The integrated model can be used for design and optimisation purposes. Because it was difficult to find an HD greenhouse where the accuracy of the integrated model can be tested, the three sub-models were tested separately. When the simulation results were confronted against the experimental results, a good accuracy was obtained for the three sub-models. It was found that the HD greenhouse model was able to predict the humidification rate with a good accuracy within the range of conditions used for calibration. The model was, then, used to simulate a hypothetical Quonset-type cucumber-cultivated greenhouse using weather data obtained from the site of the HD greenhouse in Oman. The simulation results were similar to the expected results.The applications and limitations of the HD greenhouse model are discussed in this study. Future investigations to further study and, if necessary, improve the accuracy of the HD greenhouse are highly recommended

GIS and remote sensing techniques in Controlled Environment Agriculture: A review

Geographic Information System (GIS) and Remote Sensing (RS) are useful tools in environmental monitoring, evaluation and analysis for various sectors including agriculture. This paper reviews the applications of GIS, RS and the integration of both techniques in the agricultural field, in general, and Controlled Environment Agriculture (CEA), in particular. More emphasis is given to their applications in arid areas and Oman is taken as a case study. GIS techniques have been used in the mapping of soil and water quality, spatial assessment for water quantity stress, land suitability, pest and disease distribution of crops as well as delineating and generating database management systems (DBMS) for protected cultivations. In Oman, GIS was only employed to analyse the spatio-temporal dynamics of land use changes as affected by external factors and greenhouses as an example in northern part. RS was also utilised to map the changes in land cover and their uses, detect and map soil salinity, and monitor agricultural droughts. In CEA, RS was utilised for mapping, detection and classification of greenhouses through aerial images and satellites. In Oman, negligible study was documented on the use of RS techniques in the CEA field. The integration of both techniques has proven its capability in mapping, evaluating and managing natural resources and greenhouse distribution and generating database management system in agriculture and CEA fields. Sophisticated geostatistical analysis models based on Multi-criteria analysis using Fuzzy-logic and Analytic Hierarchy Process could be a good platform for trade-off analysis for land suitability analysis and optimal location of CEA in challenging agriculture like Oman

Evaluation of Greenhouse Cucumber Production Sustainability in Terms of Energy Use Efficiency

Sustainable agricultural production could be assessed through energy-use efficiency (EUE). Thus, this paper aims to evaluate the EUE for cucumber greenhouse production in Oman. Data were obtained by interviewing farmers (face-to-face). Result indicated that total energy inputs (e.g. electricity, water, fertilizers and agrochemicals) and total energy output (cucumber yield) were 1159726.0 MJ ha-1 and 89942.9 MJ ha-1, respectively. The highest energy consuming input in the greenhouse production was electricity, consuming 88% of total energy input. This indicates that electricity had again the highest impact in cucumber greenhouse production and 99% of electricity goes for cooling the greenhouse. When all energy inputs were classified into its forms; direct (D) and indirect (ID), and renewable (R) and non-renewable (NR), the highest portion of total energy forms in greenhouse cucumber production was for D and NR energy. The EUE and energy productivity (EP) were found to be 0.07 and 0.10 kg MJ-1, respectively. Energy use in greenhouse cucumber production was inefficient and solar energy need to be implemented to improve cucumber greenhouse sustainability production

Microbiological Assessment of Locally Dried Fish in Oman: Technical Note

During fish drying process, elements and processes that affect the quality of dried fish might take place. The traditional sun-drying approach incurs major losses of the dried fish in terms of quantity and quality. Dried fish also suffer from insects and sand contamination as well as high concentration of ash especially when fish is dried on sand. The presence of microorganisms is another major factor affecting the quality of dried fish. In this project, a number of analytical tests were used to verify the presence of biochemical contamination in dried fish, as well as to propose an engineering solution to reduce the incidence of these contaminations. Two types of fish samples (anchovy and kingfish) were collected from two local markets (Buraimi and Seeb). The parameters analyzed included Total Fungal Count (TFC), Total Viable Count (TVC) and enumeration of E. coli, Staphylococcus aureus and Coliforms species in dried fish. Results showed the presence of 3 types of bacteria; E. coli, staphylococcus aureus, and coliforms in anchovy samples more than in kingfish (locally known as “Owal”) samples from both places. The kingfish samples from both places showed the presence of fungi at very small quantities (TFC<2000 cfu/ml) while the anchovy brought from Buraimi market had much more fungi which was relatively more than that brought from Seeb market. From the above results, great concern has to be made when purchasing dried fish. We recommend to dry fish under more hygienic conditions and to use solar driers instead of direct drying on beach sands

Experimental investigation of shrinkage and microstructural properties of date fruits at three solar drying methods

The effect of solar drying methods on shrinkage and the corresponding influence on microstructural changes of dates at three ripening stages (khalal, rutab and tamr) were investigated and evaluated shrinkage models that are best describing the shrinkage behavior. Drying was accomplished by forced convective solar dryer, greenhouse tunnel dryer and open sun drying. It was observed that, the greenhouse tunnel dryer had 37, 38 and 38% lower drying time for khalal, rutab and tamr stage dates, respectively compared to open sun drying, whereas the drying time was lower by 15, 29 and 30%, respectively in forced convective solar dryer. The drying methods and ripening stages had significant effect on shrinkage attributes of dates. Dates dried in the forced convective solar dryer had the lowest percentage of shrinkage in length (7–9%), diameter (10–27%) and volume (25–51%) at the three ripening stages followed by greenhouse tunnel dryer (7–13%, 12–27% and 29–53%, respectively) and open sun drying (8–13%, 17–32% and 37–60%, respectively). The quadratic equation was proposed as the best model to describe the volumetric shrinkage of dates as a function of moisture content or moisture ratio at the three ripening stages for all the three drying methods. Microstructural analysis of date tissue revealed that forced convective solar dryer had the least structural deformation at the three ripening stages. Overall, forced convective solar dryer produced the best quality of dried dates

Effect of solar drying methods on color kinetics and texture of dates

The present work investigates the effect of solar drying methods on the color and textural attributes of Khalas dates at three ripening stages (khalal, rutab and tamr) and evaluates color change kinetics using three kinetic models. Three solar drying methods, namely, open sun drying (OSD), forced convective drying (FCD) and greenhouse tunnel drying (GTD) were studied. The drying methods and ripening stages had significant effect on all color attributes. Khalal stage dates dried in FCD had the lowest color variations (L*: −12%, a*: +4%, b*: −46%, chroma: −38%, hue angle: −21% and total color change, ΔE:14.05) and thus, the highest color stability. At the end of drying, color of rutab and tamr stage dates changed red-brown in all the three drying methods due to the massive loss of b* (88–92%) and hue angle (63–73%), and altering hue angle from 23° (tamr fresh) to 9–12° (dried), respectively. The most appropriate model to describe the color change kinetics of dates at the three ripening stages was the fractional conversion model. The texture profile analysis revealed that FCD produced the softest dates for all the three ripening stages (hardness ranged 2.52–3.42 N). Overall, dates dried in FCD had the best color and textural properties as compared to the OSD and GTD dried dates in all ripening stages

Nutritional Value of Vegetable Wastes as Livestock Feed

ABSTRACT: A study was carried out to evaluate the nutritional value of waste from lettuce, green cabbage, red cabbage and cauliflower to determine their potential use for feeding to livestock. Vegetable wastes were dried in a solar tunnel drier. The crude protein (CP), ether extract (EE), total ash, acid detergent fiber (ADF) and neutral detergent fiber (NDF) were 24.1, 2.7, 24.7, 29.3 and 29.0%; 17.7, 2.3, 13.7, 25.6, and 28.7%; 11.9, 1.9, 8.8, 23.1 and 25.6%; 10.3, 0.5, 7.0, 16.1 and 19.6 % (DM basis) in cauliflower, lettuce, green cabbage and red cabbage, respectively. The gross energy (MJ/kg DM) in cauliflower  and green cabbage (16.9 and 16.6) was higher than that observed in red cabbage and lettuce (14.1 and14.3). The red and green cabbage waste had higher net gas production (73 and 71 ml/g DM/12h) compared to the lettuce and cauliflower vegetable waste (51 and 48 ml/g DM/12h respectively). The green and red cabbage waste had significantly higher metabolizable energy (ME) (approximately 12 MJ/kg DM) than both lettuce and cauliflower waste (approximately 9 MJ/kg DM). The in vitro DM and OM digestibility (OMD) in green and red cabbage waste was significantly higher than in lettuce and cauliflower. The green and red cabbage waste had significantly higher short chain fatty acids (SCFA) (1.7 and 1.6 µmol) than lettuce and cauliflower (1.2 and 1.1 µmol). It was concluded that leafy vegetable waste (lettuce, green cabbage, red cabbage and cauliflower) is an excellent source of nutrients which can potentially be used after drying as an animal feed to reduce animal feeding costs and consequently increase farmers’ profits. This would also help in waste management and the reduction of environmental pollution

Enhancement of freshwater production of the seawater greenhouse condenser

Seawater greenhouse (SWGH) is a technology established to overcome issues related to open field cultivation in arid areas, such as the high ambient temperature and the shortage of freshwater. It adopts the humidification-dehumidification concept where evaporated moisture from a saline water source is condensed to produce freshwater within the greenhouse body. Various condenser designs are adopted to increase freshwater production in order to meet the irrigation demand. The aim of this study was to experimentally investigate the practicality of using the packed-type direct contact condenser in the SWGH to produce more freshwater at low costs, simple design and high efficiency, and to explore the impact of the manipulating six operational variables (inlet air temperature of the humidifier, air mass flowrate of the humidifier, inlet water temperature of the humidifier, water mass flowrate of the humidifier, inlet water temperature of the dehumidifier and water mass flowrate of the dehumidifier) on freshwater condensation rate. For this purpose, a direct contact condenser was designed and manufactured. Sixty-four full factorial experiments were conducted to study the effect of the six operational variables. Each variable was operated at two levels (high and low flowrate), and each experiment lasted for 10 min and followed by a 30-min waiting time. Results showed that freshwater production varied between 0.257 and 2.590 L for every 10 min. When using Minitab statistical software to investigate the significant variables that contributed to the maximum freshwater production, it was found that the inlet air temperature of the humidifier had the greatest influence, followed by the inlet water temperature of the humidifier; the former had a negative impact while the latter had a positive impact on freshwater production. The response optimizer tool revealed that the optimal combination of variables contributed to maximize freshwater production when all variables were in the high mode and the inlet air temperature of the humidifier was in the low mode. The comparison between the old plastic condenser and the new proposed direct contact condenser showed that the latter can produce 75.9 times more freshwater at the same condenser volume