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The fish processing sector contributes serious organic pollution loads and high salinity to receiving waters. This research aimed to study the effect of salt (NaCl) concentration on the treatment efficiency of fish processing wastewater in a continuous flow system by natural biodegradation. This research also focused on the use of a laboratory-scale bioreactor, which is operated in an aerobic continuous flow system with a 5-day cycle treatment of three different concentrations of diluted fish processing wastewater (30-, 50-, and 100-fold) with salt concentrations varying from 0% to 7% w/v NaCl. The evaluation of system performance at nine different operating hydraulic retention times (HRT) that range from 2-10 days indicated that the substrate removal rates increase with the increase in HRT along with the increasing wastewater concentration. The optimum biomass yield was found at the 8-day HRT, and the highest substrate removal was obtained at 10-day HRT. The study on 11 different salt contents in wastewater at the optimal HRTs of 10, nine, and eight days showed the existence of inhibition effects on biomass growth and substrate removal from 3.0% salt concentration. The treated wastewater without offensive odor is feasible for its reutilization as an environmental friendly liquid fertilizer.

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A readily biodegradable substrate was used to assess the value of using a mathematical function of y = y max exp m/x as a simplified method of determining the maximum methane production (G max ) in a batch anaerobic reactor. Experimental results to test the method used three different initial substrate loadings in pre-acclimatised completely mixed anaerobic reactors. Gas production was found to follow a typical trend that has previously been described by first order reaction kinetics; for the purpose of fitting the linearisation, it requires a value for maximum cumulative methane production. Use of the modified specific function to yield the equation G = G max exp m/t showed that the experimental gas production curve could be estimated with a high degree of similarity. This was confirmed by a statistical analysis using the method of residuals which gave a correlation coefficient (R 2 ) greater than 0.97 between experimental and estimated values. Using a graphical linearisation of the specific function produced a simplified method of predicting G max . The value obtained was then used in a first order kinetic model to derive the specific coefficient rate (K o ), which was in agreement with other methods used for its determination.

Optimization of process variables in activated carbon preparation by microwave heating for reduction of energy use aiding sustainable development.