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The major sources of waste from aquaculture operations emanates from fish or shellfish processing and wastewater generation. A simple technique called coagulation/flocculation utilizes biowaste from aquaculture to produce chitosan coagulant for wastewater treatment. A chemical method was applied in the present study for chitin and chitosan extraction from carapace of Macrobrachium rosenbergii and subsequent application for removal of turbidity and salinity from shrimp aquaculture wastewater. Box-Behnken in RSM was used to determine the optimum operating conditions of chitosan dosage, pH, and settling time, after which quadratic models were developed and validated. Results show that 80 g of raw powder carapace yielded chitin and chitosan of 23.79% and 20.21%, respectively. The low moisture (0.38%) and ash (12.58%) content were an indication of good quality chitosan, while other properties such as water-binding capacity (WBC), fat-binding capacity (FBC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM) confirmed the structure and the α-group, as well as the rough morphology of chitosan. In addition, the high solubility (71.23%) and DDA (85.20%) suggested good coagulant potentials. It was recorded in this study that 87.67% turbidity was successfully removed at 20 mg/L of chitosan dosage and 6.25 pH after 30 min settling time, while 21.43% salinity was removed at 5 mg/L of chitosan dosage, 7.5pH, and 30 min settling time. Therefore, the process conditions adopted in this study yielded chitosan of good quality, suitable as biopolymer coagulant for aquaculture wastewater treatment.

The cost of picking the agriculture product is probably the major factor in determining whether or not there will be an economically successful season for most farmers. Hand harvesting has been costly, whereby, the cost of production constitute up to 80% of the total cost. Jatropha curcas has been considered as a potential feedstock for biodiesel production. Today, Jatropha curcas have been widely planted for harvesting its fruits for biodiesel production. Unfortunately, until now, the cost of jatropha production for biodiesel production is still high, especially labor costs for harvesting. The aim of the present study was to design, construct and evaluate a portable jatropha harvester to reduce dependence on human labor in the harvesting process. This smart harvester was developed by devising a simple crank powered by a hand drill 12 volt (V) that converts the rotary motion to linear motion at a push rod. To evaluate the machine performance, a factorial experiment with randomized complete randomized design (RCBD) in ten replications was conducted, the factors being shaking frequency (180, 250 and 300 rpm) and shaking duration (5, 10 and 15 seconds). To calculate the ratio of fruit detachment force (F) to its weight (W), appropriate measurements were made. Also, the geometric mean diameter of the fruits was determined at different stages of maturity. Analysis of variance (ANOVA) and comparison of means by Duncan's multiple range test (DMRT) showed that the effects of shaking frequency and shaking time on fruit detachment were greatly significant. The number of fruits detached increased by increasing the shaking frequency. Maximum number of fruits detachment was obtained by applying 300 rpm shaking frequency. Also the number of fruits detached increased by increasing the shaking duration.

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