Abstract
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.
Highlights
Water use has been growing at more than twice the rate of population increase in the last century
In the continuous reactor with various salt concentrations, the lowest Volatile Suspended Solids (VSS) increase percentage of 9.0% was found at the 9- and 10-day hydraulic retention times (HRT) in the 100-fold diluted fish processing wastewater with 7% salt content, while the highest VSS increase percentage of 50.0% was found at the 8-day HRT in the 30-fold diluted fish processing wastewater with 1% salt content
The optimum pH value, Total Suspended Solids (TSS) concentration, biomass growth, and biomass yield were found at 8-day HRT in 30-fold diluted wastewater, and the lowest were verified in the 100-fold diluted wastewater at 2-day HRT, while the optimum removal percentages of pollutants were found at 10-day HRT in 30-fold diluted wastewater, and the lowest were observed at 2-day HRT in 100-fold diluted wastewater
Summary
Water use has been growing at more than twice the rate of population increase in the last century. The need for new water resources is inevitable. The reuse of treated wastewater is one of the permanent water resources that may have numerous applications [1]. In addition to reusable water production, wastewater treatment is important for health and environment protection through the reduction of waste and production of natural fertilizer, energy and many other advantages [2,3]. We can reuse the treated wastewater for beneficial purposes such as landscape irrigation and agricultural, toilet flushing, industrial processes, and replenishing a ground water basin. The reuse of treated wastewater offers a water resource and financial savings. Wastewater treatment can be tailored to meet the water quality requirements of a planned reuse [4]
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