Variable distributional characteristics of substrate utilization patterns in activated sludge plants in Kuwait

Impact of the Biological Cotreatment of the Kalina Pond Leachate on Laboratory Sequencing Batch Reactor Operation and Activated Sludge Quality

Hauling landfill leachate to offsite urban wastewater treatment plants is a way to achieve pollutant removal. However, the implementation of biological methods for the treatment of landfill leachate can be extremely challenging. This study aims to investigate the effect of blending wastewater with 3.5% and 5.5% of the industrial leachate from the Kalina pond (KPL) on the performance of sequencing batch reactor (SBR) and capacity of activated sludge microorganisms. The results showed that the removal efficiency of the chemical oxygen demand declined in the contaminated SBR from 100% to 69% and, subsequently, to 41% after the cotreatment with 3.5% and 5.5% of the pollutant. In parallel, the activities of the dehydrogenases and nonspecific esterases declined by 58% and 39%, and 79% and 81% after 32 days of the exposure of the SBR to 3.5% and 5.5% of the leachate, respectively. Furthermore, the presence of the KPL in the sewage affected the sludge microorganisms through a reduction in their functional capacity as well as a decrease in the percentages of the marker fatty acids for different microbial groups. A multifactorial analysis of the parameters relevant for the wastewater treatment process confirmed unambiguously the negative impact of the leachate on the operation, activity, and structure of the activated sludge.

Changes of microbial substrate metabolic patterns through a wastewater reuse process, including WWTP and SAT concerning depth

In this study, changes of microbial substrate metabolic patterns by BIOLOG assay were discussed through a sequential wastewater reuse process, which includes activated sludge and treated effluent in wastewater treatment plant and soil aquifer treatment (SAT), especially focussing on the surface sand layer in conjunction with the vadose zone, concerning sand depth. A SAT pilot-scale reactor, in which the height of packed sand was 237 cm (vadose zone: 17 cm and saturated zone 220 cm), was operated and fed continuously by discharged anaerobic-anoxic-oxic (A2O) treated water. Continuous water quality measurements over a period of 10 months indicated that the treatment performance of the reactor, such as 83.2% dissolved organic carbon removal, appeared to be stable. Core sampling was conducted for the surface sand to a 30 cm depth, and the sample was divided into six 5 cm sections. Microbial activities, as evaluated by fluorescein diacetate, sharply decreased with increasing distance from the surface of the 30 cm core sample, which included significant decreases only 5 cm from the top surface. A similar microbial metabolic pattern containing a high degree of carbohydrates was obtained among the activated sludge, A2O treated water (influent to the SAT reactor) and the 0-5 cm layer of sand. Meanwhile, the 10-30 cm sand core layers showed dramatically different metabolic patterns containing a high degree of carboxylic acid and esters, and it is possible that the metabolic pattern exhibited by the 5-10 cm layer is at a midpoint of the changing pattern. This suggests that the removal of different organic compounds by biodegradation would be expected to occur in the activated sludge and in the SAT sand layers immediately below 5 cm from the top surface. It is possible that changes in the composition of the organic matter and/or transit of the limiting factor for microbial activities from carbon to phosphorus might have contributed to the observed dramatic changes in SAT metabolic patterns.

Functional diversity changes of microbial communities along a soil aquifer for reclaimed water recharge

The physiochemical and functional diversity of soil-attached microorganisms was investigated using a stabilized laboratory-scale soil aquifer treatment (SAT) system. In this system, reclaimed water after ozonation was used as the feed water, and 60% dissolved organic carbon was removed by the unsaturated vadose layer in 0.8 days. Soil biomass (volatile solids, phospholipid extraction) and functional diversity significantly decreased from the unsaturated vadose layer to the saturated aquifer, where they maintained the same level. Using principal components analysis based on substrate utilization pattern, the vadose layer soil sample was clearly separated from the saturated layer samples. Exceptionally, the oxidation rates of esters remained stable during SAT, indicating the purification potential on certain recalcitrant organic compounds in the saturated aquifer given an adequate retention time. Correlation analysis revealed that organic carbon was the key limiting factor for microbial biomass and activity, especially for tyrosine-like aromatic proteins and soluble microbial byproduct-like materials.

Bacterial community dynamics in a functionally stable pilot-scale wastewater treatment plant

To determine whether functional stability was correlated with a stable microbial community structure in a functionally stable pilot-scale wastewater treatment plant, bacterial communities in the system were monitored over a one-year period. Bacterial community dynamics was characterized by the terminal restriction fragment length polymorphism (T-RFLP) of 16S rRNA genes. During the study period, the effluent BOD concentrations were very stable, with the average BOD concentration below 10 mg/L. The effluent TN concentrations were always below 20 mg/L, except for the first 40 days. T-RFLP results showed that, during the test period, the bacterial community structures were not stable, with an average change rate (every 15 days) of 20.4%±11.2%. Based on Lorenz distribution curves, it was observed that 20% of the species corresponded with 40-77% of cumulative relative abundances. Results clearly revealed that, in the pilot-scale wastewater treatment plant, functional stability did not correlate with stable bacterial communities.