Search

This study aims to optimize nitrate (NO3-) production from synthetic aquaculture wastewater in the high-rate aerobic reactor (HRAR) for hydroponic spinach growth. The high-rate aerobic condition (Dissolve Oxygen: 5-6 mg/L) was tested in a batch diffused aerator with a pH of 5-8 while the biomass concentration and hydraulic retention time (HRT) varied 2-8 g/L and 1-5 hr. As a consequence of the batch tests, an optimum operating condition for the HRAR was determined, and the effluent containing NO3 was subsequently utilized to grow spinach in a hydroponic system. After a longer operation, an optimal condition was defined as a biomass concentration of 4 g/L and HRT of 4 hr, with a pH value ranging from 7 to 8. At this condition, NO3- production could reach up to 10 mg/L within this condition with a nitrification rate of around 0.68 mg/g Biomass.hr, whereas chemical oxygen demand (COD) and ammonia (NH3+) removal in the HRAR system was 78.8% and 88.4%, respectively. The effluent containing NO3- could grow the spinach in a hydroponic system with the mean weight and length increasing rate of 0.75 g/spinach.d and 0.47 cm/spinach.d. In this case, the mean NO3- consumption rate was estimated at 0.41 mg/spinach.hr. Besides that, the COD and NH3 removal could increase by 6.2% and 4.9% due to the activity of microbes, which were attached to the sponge culture. To sum up, the HRAR operating under neutral to alkaline conditions, HRT of 4 hr, and biomass concentration of 4 g/L could simultaneously optimize NO3 production and remove organic and nitrogen with high removal efficiency. Within the amount of the NO3 production, the spinach produced in the soilless growth method could be harvested within 4 weeks of cultivation. [ABSTRACT FROM AUTHOR]

Electrocoagulation-flotation (ECF) process has been considered as a promising wastewater method for treating turbidity, color, and oil. However, the simultaneous investigation of all three contaminants and the effect of enhanced aeration on the treatment performance are still certainly limited. Hence, this study aims to optimize the treatment condition and evaluate the removal efficiency of turbidity, color, and oil using aerated electrocoagulation-flotation reactor (AECFR). The experiments were conducted in 12-litter rectangular column as an internal-loop airlift reactor with air sparger at bottom of riser center. Two electrode plates (5 cm x 10 cm x 0.2 cm) in monopolar were connected to direct current (DC) generator. Electrode types (iron-Fe and aluminum-Al), electrode gap (2 – 6 cm), voltage (10 – 30 V), aeration rate (0.5 – 2.5 L/min), and electrolyze time (10 – 70 mins) were investigated in optimization experiment. However, the main effective variables, i.e., voltage level and electrolyze time were extended with the variation of initial concentration in the treatment kinetic study compared to effluent standard. The optimization results showed that using Al electrodes resulted in higher turbidity and color removal approximate 1% – 20% compared to Fe electrodes. Electrode gap, voltage, and electrolyze time statistically effect on turbidity and color removal efficiency (p-value<0.05), while gas flow was not. Moreover, the optimum condition found are Al electrodes, 30 V of supplied voltage, 2 cm of electrodes gap, 70 min of electrolyze time, and 0.5 L/min air flow rate. Under optimum condition, turbidity and color can be removed up to 99% and 20%, respectively. The kinetic experiment was then conducted with the variation of initial concentration and supplied voltage along the treatment time. It was found that under 30 V supply, 150, 350, and 550 NTU initial turbidity can removed to ≤20 NTU within 30, 50, and 70 min electrolyze time, respectively. Under different voltage supplies (30 – 100 V), turbidity removal showed a similar performance. It might be due to the sufficient coagulant produced under 30 V condition, and over dose at higher voltage (> 30 V). For color with 100 V, 200, 300, and 400 PCU initial color concentration can be decolorized to ≤50 PCU within 150, 270, and 380 min, respectively. Plus, decreasing voltage from 100 V to 65 V, the efficiency of color removal to ≤50 PCU increasingly requires from 270 to 350 min. Under the optimum condition of turbidity and color, oily wastewater within initial concentration 236±3 mg/L can be treated to ≤60 mg/L with≥65 V and≥80 min treatment time. Lastly, the empirical correlations were constructed for future estimation. [ABSTRACT FROM AUTHOR]

This study aims to optimize the system configuration and operation condition of the decentralized anaerobic baffled reactor (ABR) and anaerobic filter (AF) for treating domestic wastewater. Laboratory scale of ABR consisting of 66 liters working volume with eight compartments and AF consisting of 52 liters with five compartments operated under hydraulic retention time (HRT) of 24 – 48 hr. For ABR, the inlet and outlet between each compartment were varied between 3 and 9 cm height while foam and ceramic filters were used in the AF system as attached growth and filter media. Within all operation conditions, the pH value in all reactors was around the neutral condition, 6.8 – 7.2, sufficient for microbial survival and organic and nitrogen degradation activity. For the ABR, the optimum condition was obtained under 48 hr HRT and 3 cm height of inlet and outlet between each compartment. In this case, total suspended solids (TSS) and chemical oxygen demand (COD) removal efficiencies were up to 93% and 92%, respectively. It can note that obtained optimum condition provided about 4% – 23% higher than other conditions. Likewise, AF operating with foam medium was found as an optimum condition. COD and TSS removal in AF could reach 92% and 91%, respectively, while other conditions provided only 82% – 89%. However, both systems are commonly designed for anaerobic digestion only; fluctuation of nitrogen removal could reveal the presence of active microorganisms, which has responded to ammonia, nitrate, and nitrite removal. In summary, the HRT of 48 hr in ABR and AF could highly remove organic compounds from domestic wastewater. The 3 cm heigh of inlet and outlet from each compartment could enhance the contact time between wastewater and sludge. At the same time, the foam medium could act simultaneously as attached growth media and filter. Moreover, six compartments of ABR and two compartments of AF could treat domestic wastewater to reach the effluent standard of Cambodia. [ABSTRACT FROM AUTHOR]

Since it is presently impossible to compare the performance of different anaerobic treatment systems under the same operating conditions, this study aims to provide a comprehensive performance analysis of septic tank (ST), anaerobic baffled reactor (ABR), and anaerobic filter (AF) with a further comparison of the performance among the systems limited to total suspended solids (TSS) and chemical oxygen demand (COD) removal efficiency under medium-strength wastewater condition. The experiment was conducted over 4 conditions with combined variations of hydraulic retention time (HRT) of 24 – 48 hr and sludge concentration of 10 – 20 g/L of MLSS, while sponge filter media (25 ppi) was selected for the AF system. ST provided overall COD and TSS removal efficiencies of approximately 71%±9% and 65%±20%, respectively. ABR achieved 83%±5% of COD and 73%±15% of TSS, whereas AF reactor attained 85%±4% and 76% ± 11%, respectively. Extended HRT from 24 hr to 48 hr provides significant removal efficiency enhancement to all three systems over COD removal but insignificant for TSS removal. AF proves to be the best system among the three options, followed by ABR and ST. Both AF and ABR provided considerably high treatment efficiency with HRT of 24 hr. In COD removal, ST follows far behind and still see an increase with prolonged HRT, a clear indication of HRT for 48 hr or longer is recommended or required. The concentration of approximately 10 g/L of MLSS in the system (first compartment) could probably be high enough for all three systems to provide satisfactory treatment efficiency in terms of COD, while higher concentration would increase TSS removal efficiency but not COD. [ABSTRACT FROM AUTHOR]