Pretreatment of septic tank wastewater by packed anaerobic baffled reactor: Pollutant degradation and microbial community succession in different compartments

Iron-retrofitted anaerobic baffled reactor system for rural wastewater treatment: Stable performance of nutrients removal with phosphorus recovery and minimal sludge production

An iron-retrofitted anaerobic baffled reactor (ABR) system was developed for the effective treatment of rural wastewater with reduced maintenance demand and aeration costs. Average removal efficiencies of chemical oxygen demand, total nitrogen and total phosphorus of 99.4%, 62.7% and 92.6% were achieved respectively, when the ABR system was operating at steady state. With effective bioreduction of FeIII in the anaerobic chambers, phosphorus was immobilized in the sludge as vivianite, the sole phosphorus-carrying mineral. The FeIII in the recirculated sludge induced Feammox in the ABR reactor, contributing 14.8% to total nitrogen removal. Biophase separation and enrichment of microorganisms associated with iron and nitrogen transformations were observed in the system after Fe dosing, which enhanced the removal of pollutants. The coupling of Feammox and vivianite crystallization to remove nitrogen and phosphorus in an iron-retrofitted ABR would appear to be a promising technology for rural wastewater treatment.

Reliability of organic and biogenic pollutant removal in selected technologies used in domestic wastewater treatment plants: A comparative analysis

The results of a comparative study of two different technological solutions applicable to decentralised domestic wastewater treatment systems are presented. A hybrid reactor with activated sludge and mobile biofilm carriers moving in wastewater is one of them, and an innovative quasi-technical combination of a biological reactor with a sprinkled bed filled with sintered clay granules, followed in the process line by an innovative slope type filtration bed, is the other one. The study has shown a significant advantage of filter bed installations in functional quality, expressed in low values of indicators and pollutant concentrations. In the comparison of technological reliability and probability of exceeding the requirement values of BOD5 = 40 mg/L, Facility 1 achieved technological reliability of 70% and probability of exceeding was 23%. Technological reliability of Facility 2 in this component was 100% and P = 0%. Both facilities presented 100% technological reliability in the COD indicators, with zero probability of exceeding the required value of 150 mg/L. The reliability of TSS removal was similarly high in both facilities: 91% and 100%. The higher functional quality of Facility 2 was evident in TN and PO4-P parameters, where the period of its operation with exceeded values did not exceed 20% and 13%, respectively, with a low probability of exceeding the value of 18% and 2.5%, respectively. However, Facility 1 was unreliable in this regard in 90% and 84%, with a very high probability of exceeding the required values of these parameters: 88% and 72%. This facility does not meet the required criteria in this respect and may cause a risk to the aquatic environment if wastewater is discharged directly into open watercourses, or if it enters shallow groundwater. The use of a suitable, biologically active soil-plant receiver can eliminate this risk.

Simultaneous methanogenesis and denitrification in an anaerobic moving bed biofilm reactor for landfill leachate treatment: Ameliorative effect of rhamnolipids

In this study, an anaerobic moving bed biofilm reactor (AnMBBR) was developed for simultaneous methanogenesis and denitrification (SMD) to treat high-strength landfill leachate for the first time. A novel strategy using biosurfactant to ameliorate the inhibition of landfill leachate on the SMD performance was proposed and the underlying mechanisms were explored comprehensively. With the help of rhamnolipids, the chemical oxygen demand (COD) removal efficiency of landfill leachate was improved from 86.0% ± 2.9% to 97.5% ± 1.6%, while methane yields increased from 50.1 mL/g-COD to 69.6 mL/g-COD, and the removal efficiency of NO3--N was also slightly increased from 92.5% ± 1.9% to 95.6% ± 1.0%. The addition of rhamnolipids increased the number of live cells and enhanced the secretion of extracellular polymeric substances (EPS) and key enzyme activity, indicating that the inhibitory effect was significantly ameliorated. Methanogenic and denitrifying bacteria were enhanced by 1.6 and 1.1 times, respectively. Analysis of the microbial metabolic pathways demonstrated that landfill leachate inhibited the expression of genes involved in methanogenesis and denitrification, and that their relative abundance could be upregulated with the assistance of rhamnolipids addition. Moreover, extended Deraguin - Landau - Verwery - Oxerbeek (XDLVO) theory analysis indicated that rhamnolipids reduced the repulsive interaction between biofilms and pollutants with a 57.0% decrease in the energy barrier, and thus accelerated the adsorption and uptake of pollutants onto biofilm biomass. This finding provides a low-carbon biological treatment protocol for landfill leachate and a reliable and effective strategy for its sustainable application.