Effect of photovoltaics shading on the growth of chili pepper in controlled greenhouses.

The integration of photovoltaic into a greenhouse has been implemented to maximize the energy output and crop production yield from the same land space. The effect of greenhouse external shading of opaque crystalline silicon photovoltaic (PV) panels at 13-26% of the roof area on the microclimate and growth of Chili pepper Capsicum annuum cv. (omega) was investigated. The PV panels were divided into two arrays (each of 4 PVs) and fixed separately on two external pillars of 4 m height in the Southeast and Northwest directions, respectively. Each array of 4 PVs could be tracked from the East-West direction to North-South. There were two greenhouses, one was used as control without shading and the other had the external shading. The results revealed that the external shading of PV slightly decreased air temperatures (1-2 °C) and light intensities (25-40%) but had no effect on the dew point temperatures and relative humidity as compared to the control (unshaded greenhouse). Furthermore, the yield and growth of Chili pepper in the shaded greenhouse was insignificantly higher than that in the unshaded greenhouse. Moreover, the simulation results revealed that the estimated electric energy of photovoltaic panels was 3705 kWh/year at a tilt angle of 25° facing South.

Effect of flow characteristics on online sterilization of cheese whey in UV reactors.

An ultraviolet (UV) coil reactor was designed and used for the online sterilization of cheese whey. Its microbial destruction efficiency was compared to that of the conventionally used UV reactor. Both reactors have the same geometry (840 ml volume and 17 mm gap size) and were tested at 11 flow rates of 5, 10, 15, 20, 25, 30, 35, 40, 50, 60, and 70 ml/min. The results obtained from this study showed that despite of its high turbidity, cheese whey could be sterilized using UV radiation if the proper reactor design and flow rate are used. The performances of the UV reactors were governed by the flow rate and the hydraulics of flow inside the reactor. The flow was laminar in both the reactors, as the Reynolds number was in the range of 1.39-20.10. The phenomenon of Dean Flow was observed in the coil reactor and the Dean number was in the range of 1.09-15.41. Dean vortices resulted in higher microbial destruction efficiency in the coil reactor in a shorter retention time. The rate of microbial destruction was found to be exponential in the conventional reactor and polynomial in the coil reactor. Increasing the flow rate from 5 ml/min to 70 ml/min decreased the microbial destruction efficiency of the conventional reactor from 99.40 to 31.58%, while the microbial destruction efficiency in the coil reactor increased from 60.77% at the flow rate of 5 ml/min to 99.98% at the flow rate of 30 ml/min and then decreased with further increases in flow rate reaching 46.2% at the flow rate of 70 ml/min. The maximum effluent temperatures in the conventional and coil reactors were 45.8 and 46.1 degrees C, respectively. Fouling in the coil reactor was significantly less compared to the conventional reactor. The extent of fouling was influenced by flow rate and reactor's hydraulics.

Effects of tetrazolium chloride concentration, O2, and cell age on dehydrogenase activity of Aspergillus niger.

The effects of triphenyl tetrazolium chloride (TTC) concentration, cell age, and presence of O2 on the dehydrogenase activity of Aspergillus niger as measured by triphenyl formazan (TF) yield were investigated. The results indicated that increasing TTC concentration initially increased the TF yield and then decreased it. The maximum TF yield was observed at a TTC concentration of 30 g/L for young cells (4 d old) and 20 g/L for old cells (12 d old). Conducting the test under anaerobic conditions increased the TF yield. About 18% of the TF produced was converted back into TTC in the presence of oxygen. The relationship between dehydrogenase activity of A. niger (as measured by TF yield) and cell mass was found to be linear. A kinetic model describing the relationship between reaction rate (micromoles of TF formed per hour) and TTC concentration while accounting for substrate inhibition was developed, and the model constants were calculated. The optimum TTCtest conditions for dehydrogenase activity measurement of A. niger were a TTC concentration of 20 g/L, a pH of 9.0, a temperature of 55 degrees C, an incubation time of 3 h, and anaerobic conditions.

Reduced fouling and enhanced microbial inactivation during online sterilization of cheese whey using UV coil reactors in series.

The effectiveness of coil UV reactor series for the online sterilization of cheese whey was compared to those of the single conventional and coil reactors at various flow rates (5-70 mL/min). The residence time varied from 168 to 12 min and from 48 to 24 min for the single and the series reactors, respectively. Hundred percent destruction efficiency could not be achieved in the single reactors whereas in the coil reactor series the destruction efficiency reached 100% at the flow rates of 35 and 40 mL/min. The rate of microbial destruction was described by polynomial equation for the single coil reactor and by exponential equations for the single conventional reactor and the coil reactor series. The temperature of the effluent decreased with the increase in flow rate in all the reactors. The maximum effluent temperatures in the single conventional reactor, single coil reactor and coil reactor series were 45.8, 46.1, and 36.4 degrees C (Deltat = 20.8, 21.1, 11.4 degrees C), respectively. The flow in all the reactors was laminar (R ( e ) = 1.39-20.10) and the Dean number was in the range of 1.09-15.41 in the coil reactors. Visual observation revealed less fouling on the UV lamps of coil reactors than on that of the conventional reactor due to the impact of Dean flow. The total operating time during which 100% destruction efficiency is achieved prior to the advent of fouling was 240 min in the coil reactor series compared to only 45 min in the conventional reactor.

Inactivation of Botrytis cinerea during thermophilic composting of greenhouse tomato plant residues.

The effectiveness of in-vessel thermophilic composting on the inactivation of Botrytis cinerea was evaluated. The bioreactor operated on an infected mixture of tomato plant residues, wood shavings, and municipal solid compost (1:1.5:0.28). Tap water and urea were added to adjust the moisture content and C:N ratio to 60% and 30:1, respectively. Used cooking oil was added as a bioavailable carbon source to compensate for heat losses from the system and extend the thermophilic composting stage. The controlled thermophilic composting process was successful in inactivating B. cinerea. During all experiments, the average reactor temperature increased gradually, reaching its peak after 31 h of operation. Temperatures in the range of 62.6-63.9 degrees C were maintained during the thermophilic stage by the intermittent addition of used cooking oil. The results of the enzyme-linked immunosorbent assay test indicated that the initial concentration of B. cinerea in the compost samples (14.6 mug of dried mycelium/g of compost) was reduced to 12.9, 8.8, and 2.4 mu/g after 24, 48, and 72 h of thermophilic composting, respectively. Plating assay indicated that the mold was completely inactivated in samples after 48 h of thermophilic composting. No significant reduction in B. cinerea was observed during the transient phase (first 30 h of rising temperature) because the temperature reached the lethal level of 55 degrees C after 23 h, thus allowing only 7 h of exposure to temperatures higher than 55 degrees C during this phase. The relatively short time required for complete inactivation of B. cinerea was achieved by maintaining a constant high temperature and a uniform distribution of temperature and extending the duration of the thermophilic stage by the addition of the proper amount of bioavailable carbon (used cooking oil).

Influence of dairy manure addition on the biological and thermal kinetics of composting of greenhouse tomato plant residues.

A laboratory-scale bioreactor was used to investigate the influence of dairy manure addition (as an inoculum and a carbon source) on the biological and thermal kinetics of the composting process of tomato plant residues-wood shavings mixture. Urea was added (as a nitrogen source) to correct the initial C:N ratio to 30:1 and the initial moisture content was also adjusted to 60%. The result of this study indicated that manure addition to the tomato residues-wood shavings mixture is a good source of macro and micronutrients required for supporting the composting microorganisms. Manure addition increased the rate of temperature increase and the duration of maximum temperature and reduced the lag and the peak time, all of which resulted in a significant reduction in the retention time. However, thermophilic temperature (> or = 40 degrees Celsius) was only achieved with 30%, 40% and 50% manure addition for 3, 7 and 9h. Total carbon reductions were in the range of 9.4-10.8% and TKN reductions were in the range of 3.4-6.0%. Neither the nitrogen nor the moisture content were limiting factors as the C:N ratio remained in the range of 26:1 to 28:1 and the moisture content remained within the optimum range of 58-61%. The maximum temperature of each mixture correlated with the reduction of total carbon, but carbon availability was a limiting factor in these experiments. In order to attain and sustain a thermophilic phase during the composting process, the addition of a readily available carbon source to the tomato should be investigated and carbon type (carbohydrates, proteins and fats) should be taken into account.

Organic and inorganic fouling at quartz-liquid interface in ultraviolet photoreactors during on-line sterilization of cheese whey.

This article reports on lamp fouling during on-line ultraviolet (UV) sterilization of cheese whey. The extent of fouling as well as the composition of fouling materials was studied after the operation of three tubular UV reactors of different flow thicknesses (18, 13, and 6 mm) for 48 h at a 2-h residence time. Lamp fouling, which significantly affected the sterilization efficiency, was realized after an extended period of operation. The extent of lamp fouling increased with a decrease in the thickness of the flowing cheese whey (14.42, 15.31, and 25.25 g for 18-, 13-, and 6-mm thickness, respectively). A strong relationship between the extent of fouling and the steady-state outlet temperature was observed. The fouling material contained 63.51 to 77.19% protein, 12.57 to 16.49% fat, and 6.51 to 9.47% minerals on dry weight bases compared with 1% protein, 0.5% fat, and 0.4% minerals in raw cheese whey. The organic and inorganic material concentrations in the fouling material increased with a decrease in the flow thickness. The fouling mechanism was owing to adsorption and direct ion exchange, which were enhanced by the high temperature and low pH attained in the study. Improved designs of UV reactors in which the contact between the flowing material and the quartz surface should be developed.

Kinetic modelling of continuous submerged fermentation of cheese whey for single cell protein production.

A mathematical model describing the kinetics of continuous production of single cell protein from cheese whey using Kluyveromyces fragilis was developed from the basic principles of mass balance. The model takes into account the substrate utilization for growth and maintenance and the effect of substrate concentration and cell death rate on the net cell growth and substrate utilization during the fermentation process. A lactose concentration below 1.91 g/L limited growth of yeast cells whereas a lactose concentration above 75 g/L inhibited the growth of the yeast. The model was tested using experimental data obtained from a continuous system operated at various retention times (12, 18 and 24 h), mixing speeds (200, 400 and 600 rpm) and air flow rates (1 and 3 vvm). The model was capable of predicting the effluent cell and substrate concentrations with R2 ranging from 0.95 to 0.99. The viable cell mass and lactose consumption ranged from 1.3 to 34.3 g/L and from 74.31% to 99.02%, respectively. A cell yield of 0.74 g cell/g lactose (close to the stoichiometric value of 0.79 g cell/g lactose) was achieved at the 12 h retention time-3 vvm air flow rate-600 rpm mixing speed combination. The total biomass output (viable and dead cells) at this combination was 37 g/L.

Phytoremediation of aquaculture wastewater for water recycling and production of fish feed.

Five plants were examined for their ability to remove nutrients from aquaculture wastewater and suitability as fish feed: alfalfa, white clover, oat, fall rye, barley. The seeds were first germinated in water in a hydroponic system, and the plants were fed wastewater from Tilapia production facility. Clover and alfalfa seeds were infected with fungus shortly after germination, and their roots were completely destroyed by day 14. Oat, rye and barley had the fastest growth and showed greater tolerance to fungal disease compared with alfalfa and clover. Although substantial amounts of soluble and insoluble substances were released by the seeds during the germination period, the plants were able to remove all the pollutants in wastewater and significant portions of those released substances. The total reductions in total solids, COD, NO3-N, NO2-N, phosphate and potassium ranged from 54.7% to 91.0%, 56.0% to 91.5%, 82.9% to 98.1%, 95.9% to 99.5%, 54.5% to 93.6% and 99.6% to 99.8%, respectively. Oat, barley and rye grow well in this type of hydroponic system and can be used as a fish feed after being supplemented with fat, Ca, Na, Mn and Fe. Oil seeds and the chlorides of these elements could be added to these plants when formulating the fish feed. For a continuous operation, a two-unit system could be configured to allow for one week germination and one week cleaning and startup in one unit while the other unit is in operation.

On-line sterilization of cheese whey using ultraviolet radiation.

The effectiveness of ultraviolet radiation for on-line sterilization of cheese whey was investigated. The effects of flow rate and residence time on the performance of three UV reactors having different gap sizes (18, 13, and 6 mm) were studied. Six flow rates and six residence times were tested with the three UV reactors. The cheese whey used in this study had a very high turbidity (4317 NTU), very poor transmittance in the UV radiation germicidal range ( approximately 0%), and high percentage of large solid particles ( approximately 20% > 100 microm). Although the cheese whey physical characteristics showed low probability of sterilization using UV radiation, the study showed that UV radiation can be used on-line to sterilize cheese whey if the proper reactor gap size and the appropriate residence time are used. There were combined effects of the flow rate and gap size. The cell removal efficiency increased with increases in residence time and decreases in the UV reactor gap size. Removal efficiency of 100% was not achieved in this study with the first UV reactor (18-mm gap size), whereas 100% removal efficiency was achieved with the second (13-mm gap size) and third (6-mm gap size) UV reactors at residence times of 2.0 and 0.5 h, respectively. The microbial decay rates achieved in this study were 4.94, 7.62, and 20.9 h(-)(1) using the first, second, and third UV reactor, respectively. Residence times of 3.3, 2.1, and 0.8 h would be required to completely destruct a microbial population of 5.95 x 10(6) cells/mL using the first, second, and third UV reactors, respectively. Although cheese whey sterilization using UV radiation seems to be a good alternative to pasteurization, increases in cheese whey temperature resulted in lamp fouling. If online sterilization is to be used, the fouling problem should be investigated and a maintenance scheme for the UV reactor should be developed.

Influence of temperature and pH on the nonenzymatic reduction of triphenyltetrazolium chloride.

The effects of temperature and pH on the nonenzymatic (chemical) reduction of triphenyltetrazolium chloride (TTC) to triphenyl formazan (TF) in cheese whey and municipal solid waste compost samples were studied. Ten different incubation temperatures and 13 pH levels were tested. The study showed that the TTC could be reduced nonenzymatically at high temperatures and/or under alkaline pH conditions. The nonenzymatic TTC reduction was observed at pH values greater than 9.5 and 11.0 for the cheese whey and compost, respectively. The TTC chemical reduction rate followed the same trend in both media. The TF content increased with increasing the pH value, reaching its maximum at a pH of 12, then decreased and was not detected at a pH of 13. The TTC was also reduced nonenzymatically at temperatures higher than 70 and 85 degrees C for cheese whey and compost, respectively. Evaporation did not seem to have any significant effect on the TTC chemical reduction since less than 3% of water content was lost at a temperature of 100 degrees C. It was noticed that the TF yield in cheese whey samples was higher than that in compost samples. This was due to the higher moisture content of cheese whey and the presence of copper in the compost samples, which reacted chemically with the TF causing reduction in the red color. For a given incubation period, the effect of pH on the TTC chemical reduction was more significant than the effect of incubation temperature (at a 2 h incubation period, 57.5% and 17.9% of the TTC were chemically reduced at a pH of 12 compared to 10.9% and 7.7% at an incubation temperature of 100 degrees C, for cheese whey and compost, respectively). Among the six metals tested (Ca, Cu, K, Na, Ni, and Zn) only Cu affected the color intensity of the TF. The activation energy of the TTC chemical reduction was 168,808 and 239,102 J/mol in cheese whey and municipal solid compost, respectively. For dehydrogenase activity measurement, the pH of the samples and the incubation temperature should not be higher than 9 and 60 degrees C in order to ensure that the TTC reduction is caused only by the biochemical reaction. Measuring the color intensity of TF in waste samples that contain copper could give misleading results as a result of the formation of formazan copper complex, which reduces the red color.

Submerged yeast fermentation of acid cheese whey for protein production and pollution potential reduction.

Bench-scale batch bioreactors were used to study the effectiveness of cheese whey fermentation for single-cell protein production using the yeast Kluyveromyces fragilis in reducing the pollution potential of whey as measured by solids, chemical oxygen demand (COD) and nitrogenous compounds concentrations. The four principal phases (lag, exponential, stationary and death) encountered in the history of a microbial culture grown under batch conditions were clearly recognized in the growth, temperature and dissolved oxygen curves. The lactose concentration and soluble COD displayed three distinct phases corresponding to the lag, exponential and stationary phases of the yeast growth. The minimum dissolved oxygen and maximum temperature observed in this study (at an air flow of 3 VVM, a mixing speed of 400 rpm and an ambient temperature) were 2.49 mg/L and 31.6 degrees C, respectively. About 99% of lactose (90.6% of soluble COD) was utilized after 28 h. The total COD continued to decline due to cell death resulting in a reduction of 42.98%. The total nitrogen concentration remained unchanged while the organic nitrogen increased during the exponential phase and then declined during the death phase. The ash content remained unchanged while a substantial reduction (56%) of the volatile solids was observed. These results indicated that sufficient oxygen for yeast growth was present in the medium and no cooling system was needed for this type of fermenter under similar experimental conditions. Recovering the yeast biomass with ultrafiltration reduced the total COD by 98% of its initial value in the raw whey.

Phytoaccumulation of heavy metals by aquatic plants.

Three aquatic plants were examined for their ability to remove heavy metals from contaminated water: parrot feather (Myriophylhum aquaticum), creeping primrose (Ludwigina palustris), and water mint (Mentha aquatic). The plants were obtained from a Solar Aquatic System treating municipal wastewater. All the three plants were able to remove Fe, Zn, Cu, and Hg from the contaminated water. The average removal efficiency for the three plant species was 99.8%, 76.7%, 41.62%, and 33.9% of Hg, Fe, Cu, and Zn, respectively. The removal rates of zinc and copper were constant (0.48 mg/l/day for Zn and 0.11 mg/l/day for Cu), whereas those of iron and mercury were dependent on the concentration of these elements in the contaminated water and ranged from 7.00 to 0.41 mg/l/day for Fe and 0.0787 to 0.0002 mg/l/day for Hg. Parrot feather showed greater tolerance to toxicity followed by water mint and creeping primrose. The growth of creeping primrose was significantly affected by heavy metal toxicity. The selectivity of heavy metals for the three plant species was the same (Hg>Fe>Cu>Zn). The mass balance preformed on the system showed that about 60.45-82.61% of the zinc and 38.96-60.75% of the copper were removed by precipitation as zinc phosphate and copper phosphate, respectively.

Influence of ambient air temperature on the cooling/heating load of a single cell protein jacketed fermenter operating on cheese whey under continuous conditions.

The heat generated by mixing and lactose metabolism, during the continuous production of single cell protein from cheese whey lactose using a jacketed fermenter with running cooling water, was calculated using a heat balance equation. The technique quantified the heat produced in and lost from the fermentation unit. Most of the heat generated by mixing in the cell-free system (97.47%) was lost with exhaust gas, while a very small amount (2.53%) was lost through the fermenter lid, wall, and bottom. The heat generated by mixing was significant (26.31% of the total heat generated in the fermentation system with an active yeast population present) and, therefore, cannot be ignored in heat balance calculations. About 19.71% of the total heat generated in the reactor was lost through the coolant at an ambient temperature of 22 +/- 0.5 degrees C, showing the need for a cooling system. A yeast population size of 986 million cells/mL and a lactose removal efficiency of 95.6% were observed. About 72.5% and 27.5% of the lactose consumed were used for growth and respiration, respectively. A yield of 0.66 g of cells/g of lactose was achieved. The heat released by unit biomass was 7.05 kJ/g of cells. The results showed the significant impact of ambient air temperature on the cooling load. The heat to be removed from the medium by the cooling system varied from 3.46 to 281.56 kJ/h when the temperature increased from 16 to 30 degrees C. A heating system is needed to maintain the medium temperature at 34 degrees C when the ambient air temperature is below 16 degrees C.

A continuous lactic acid production system using an immobilized packed bed of Lactobacillus helveticus.

A 5 l packed bed bioreactor was used to study the effect of initial lactose concentration and hydraulic retention time (HRT) on cell growth, lactose utilization and lactic acid production. Up to 95% of the initial lactose concentration was utilized at longer HRTs (30-36 h). The study showed that lactic acid production increased with increases in HRT (12-36 h) and initial lactose concentrations. The highest lactic acid production rate (3.90 g l(-1) h(-1)) was obtained with an initial lactose concentration of 100 g/l and an HRT of 18 h, whereas the lowest lactic acid production rate (1.35 g l(-1) h(-1)) was obtained with an initial lactose concentration of 50 g/l and an HRT of 36 h. This suggested that optimal lactic acid production can be achieved at an HRT of 18 h and initial lactose concentration of 100 g/l.

Pollution potential reduction of cheese whey through yeast fermentation.

Batch and continuous pilot-scale aerobic fermenters of 4.8 L operating volume were designed and constructed from plexiglass materials. The fermenters were used to study the kinetics of cheese whey fermentation using the yeast K. fragilis for pollution potential reduction and single cell protein production. Four retention times (6, 12, 18, and 24 h) were used in this study. The fermentation process was successful in reducing the total chemical oxygen demand (COD) by 42%, the soluble COD by 65%, the total solids by 53%, and the ammonium nitrogen by 90%. There were also gains in the suspended solids and the organic nitrogen of 60 and 17%, respectively. The reductions in the COD, total solids, and ammonium nitrogen, and the gains in the suspended solids and organic nitrogen were affected by the hydraulic retention time. More soluble material was converted to insoluble microbial cells at the 12-h hydraulic retention time, whereas greater pollution potential reduction was achieved at the 24-h hydraulic retention time for both batch and continuous operations.

Growth rate determination of heterogeneous microbial population in swine manure.

The effect of manure concentration on the growth of the heterogeneous microbial population under batch condition was studied. Four manure concentrations were used in the study. The dehydrogenase activity was used as a measure of the active biomass in the manure. The chemical oxygen demand test was used to measure the change in organic material caused by biological activities. The growth curve of the heterogeneous microbial population in swine manure was essentially similar to that of a pure culture grown batchwise in that it had the four principle phases: lag, exponential growth, stationary, and death. The exponential growth phase followed a diauxic growth pattern. High concentration of manure had an inhibitory effect on the microbial growth. Manure diluted less than 1:3 (manure:water) depressed the specific growth rate of the microbial population.