Effect of Hydraulic Retention Time on the Performance of a Compact Moving Bed Biofilm Reactor for Effluent Polishing of Treated Sewage

Treated effluent from a wastewater treatment plant can be further reused as a water resource for a water supply treatment plant. In this case, the treated sewage gathered in the study of the Class V National Water Quality Standard (NWQS) of Malaysia would be treated for use as a water resource for a water treatment plant. In a moving bed biofilm reactor (MBBR) with a 500-L working volume, organic pollutants, undesirable nutrients, and bacteria were removed without disinfectant. At 24-h hydraulic retention time (HRT), the maximum removal efficiency of 5-day biological oxygen demand, ammonia–nitrogen (NH3-N), and total phosphorus were 71%, 48%, and 12%, respectively. The biofilm thickness, which was captured using scanning electron microscopy, increased from 102.6 μm (24-h HRT) to 297.1 μm (2-h HRT). A metagenomic analysis using 16S rRNA showed an abundance of anaerobic bacteria, especially from the Proteobacteria phylum, which made up almost 53% of the total microbes. MBBR operated at 24-h HRT could improve effluent quality, as its characteristics fell into Class IIA of the NWQS of Malaysia, with the exception of the NH3-N content, which indicated that the effluent needed conventional treatment prior to being reused as potable water.

Effect of Hydraulic Retention Time on the Levels of Biochemical Oxygen Demand and Total Suspended Solid with Simple Integrated Treatment as an Alternative to Meet the Household Needs for Clean Water

BACKGROUND: Domestic wastewater can cause health problems and pollute groundwater sources. Such pollution not only has a negative impact on health and the environment, but also on the cost in providing clean water. AIM: The outcome of domestic wastewater treatment through a proper technique is expected to meet the clean water quality standard for sanitation purposes. MATERIALS AND METHODS: The experiment was conducted to determine the effect of Hydraulic Retention Time (HRT) on the levels of Biochemical Oxygen Demand (BOD) and Total Suspended Solid (TSS) of domestic wastewater. The experiment was carried out with 6 variations of HRT, namely 1 hour, 2 hours, 4 hours, 6 hours and 8 hours with 4 repetitions. The media running process was carried out for 14 days until the reactor condition was in steady state. RESULTS: The results showed that the removal values ​​for COD, Oil and Fat, Ammonia and Total Coliform parameters were 68.03%, 46.51%, 69.64% and 68.99%, respectively. Based on the variation of HRT of 1 hour, 2 hours, 4 hours, 6 hours and 8 hours on the BOD parameter, the removal values ​​obtained were 11.7%, 21.3%, 34.7%, 49.0% and 64.1%, respectively. Furthermore, for the TSS parameter, the values obtained were 17.3%, 25.4%, 30.6%, 42.3% and 50.4%, respectively. CONCLUSION: HRT was proven to have a significant effect on the levels of BOD and TSS of domestic wastewater with a p-value of <0.05 at the 95% confidence level

Potential Nitrate Reduction Rates in Marine Mangrove Sediments in the Lesser Antilles

Mangrove sediments are generally nitrogen limited, with nitrate reduction to ammonium instead of denitrification in these sediments, resulting in nitrogen retention rather than nitrogen elimination. The goal of this work was to investigate the potential for nitrate reduction in marine mangrove sediments along a canal impacted by anthropogenic activity (Guadeloupe, West Indies) as a function of increased nitrogen load and how this would change nitrate transformation rates. In addition to that, the impact of the organic carbon load and the hydraulic retention time was assessed as factors affecting nitrate reduction rates. Potential nitrate reduction rates in the sediments along the canal, in the presence of indigenous organic carbon, ranged from 126 to 379 nmol cm‑3 h-1 generally increasing upon increasing supplied nitrate. The potential for nitrate reduction increased significantly with the addition of mangrove leaves, whereas the addition of simple, easily degradable carbon (acetate), resulted in an almost five-fold increase in nitrate reduction rates. The hydraulic retention time also had an impact on the nitrate reducing capacity due to an increased contact time between nitrate and the benthic microbial community. Marine mangrove sediments have a high potential to mitigate nitrogen pollution, mainly governed by the presence of large amounts of degradable carbon in the form of litter. The hydraulic retention time as tested experimentally that can be extrapolated to the time of inundation of the mangrove sediments may increase the potential for nitrate reduction. Whereas the sediments are daily exposed to a small tidal effect, increased water retention could increase the nitrogen elimination potential in these mangrove sediments.