The main aim of this research is to develop a mathematical model to predict the dissolved oxygen in recirculating aquaculture system. The oxygen consumption of the model through the fish respiration and nitrification and the oxygen addition of the model through oxygen generator and water pumping. The effect of different water temperatures (24, 26, 28, 30 and 32 °C) on the dissolved oxygen consumption through fish respiration, biofilter and nitrification and fish growth were studied. An experiment to measure oxygen consumed by fish respiration and biofilteration and fish growth with the growth period and to validate the model results was carried out. The oxygen consumption predicted by the model was in a good agreement with those measured by the system. The oxygen consumption by fish respiration ranged 12.04 to 47.53 g O2 m−3 h−1 experimentally, while it was from 12.01 to 46.06 g O2 m−3 h−1 theoretically. The predicted and measured oxygen consumption through biofilteration values ranged from 0.43 to 21.91 and 0.45 to 23.09 g O2 m−3 h−1, respectively. The individual fish weight from the system ranged from 3.00 to 209.52 g experimentally while it was from 3.00 to 226.25 g theoretically during the whole period.

Soilless cultivation systems that provide plant management in soilless conditions in which the supply of water and of minerals is carried out by nutrient solution, with or without a growing medium. The main aim of this paper was to investigate the possibility of growing basil under three soilless systems (aeroponic, hydroponic and peatmoss slab systems). A model was developed to predict the nutrients consumption by basil plants. Shoot and root height, fresh and dry mass of whole plant, nutrients uptake, and oil content were studied during the growth period (after 4 and 7 weeks from transplanting). The results indicated that the shoot lengths of basil plants were 62.00 ± 2.65, 57.83 ± 7.42 and 48.77 ± 2.89 cm after 4 weeks and 71.67 ± 2.89, 65.67 ± 1.15 and 62.33 ± 2.31cm after 7 weeks from transplanting for aeroponic, hydroponic and peatmoss slabs, respectively. The highest value of root height of basil plants was 37.67 ± 6.66 cm for aeroponic system. The dry mass of shoot of basil plants ranged from 28.48 ± 0.91 to 44.77 ± 0.97 and 72.98 ± 0.83 to 117.93 ± 1.40 g plant-1 after 4 and 7weeks from transplanting, respectively. The highest values of the N, P, K, Ca and Mg uptakes were 262.50 ± 6.84, 74.34 ± 2.90, 195.13 ± 4.09, 132.41 ± 1.54 and 41.81 ± 0.83 mg plant-1 and 753.99 ± 5.65, 224.88 ± 3.05, 449.75 ± 4.59, 529.12 ± 6.63 and 112.44 ± 1.67 mg plant-1 after 4 and 7 weeks from transplanting, respectively. The basil oil content ranged from 1.129 ± 0.020 to 2.520 ± 0.021 and 2.664 ± 0.291 to 6.318 ± 0.375 g plant-1 after 4 and 7weeks from transplanting, respectively at the same pervious order. The production costs of basil plant were 2.93, 5.27 and 6.24 EGP kg-1 of plant. The model results were in a reasonable agreement with the experimental ones.

A small scale washing machine with a rotating drum and a continuous pressurized water stream was developed and evaluated for root crops washing at farm after harvesting process. The performance of the developed washing machine was evaluated in potato tubers washing under three different drum speeds of 10, 20 and 30 rpm, three different batch loads of 12, 24 and 36 kg and four different retention times of 2, 4 ,6 and 8 min. Results revealed that the proper washing performance in terms of washing efficiency (93.07%), bruising percentage (5.33 %) and microbial washing efficiency (85.8 %) was achieved when the machine was operated at 20 rpm rotor drum speed, 36 kg batch load and 4 min retention time. At such proper operating parameters, the machine productivity was 0.43 Mg/h and the consumed specific energy was 3.96 kWh/Mg. To promote the developed washing prototype in small farms implementations, the potato washer production cost was estimated by 6.25 USD/Mg (100 EGP/Mg), which was less about 2.8 times than that of the manual washing process of 17.37 USD / Mg (278 EGP / Mg).