Pilot and full scale applications of floating treatment wetlands for treating diffuse pollution.

Floating treatment wetlands (FTW) are nature-based solutions for the purification of open water systems such as rivers, ponds, and lakes polluted by diffuse sources as untreated or partially treated domestic wastewater and agricultural run-off. Compared with other physicochemical and biological technologies, FTW is a technology with low-cost, simple configuration, easy to operate; has a relatively high efficiency, and is energy-saving, and aesthetic. Water remediation in FTWs is supported by plant uptake and the growth of a biofilm on the water plant roots, so the selection of the macrophyte species is critical, not only to pollutant removal but also to the local ecosystem integrity, especially for full-scale implementation. The key factors such as buoyant frame/raft, plant growth support media, water depth, seasonal variation, and temperature have a considerable role in the design, operation, maintenance, and pollutant treatment performance of FTW. Harvesting is a necessary process to maintain efficient operation by limiting the re-pollution of plants in the decay phase. Furthermore, the harvested plant biomass can serve as a green source for the recovery of energy and value-added products.

Influence of C/N ratios on treatment performance and biomass production during co-culture of microalgae and activated sludge.

Novel phycosphere associated bacteria processes are being regarded as a potential and cost-effective strategy for controlling anthropogenic contaminants in wastewater treatment. However, the underlying concern with the process is its vulnerability to improper organic or nutrient intake. This study established a synergistic interaction between microalgae and activated sludge in a three-photobioreactor system (without external aeration) to understand how pollutants could be mitigated whilst simultaneously yielding biomass under different C/N ratios of 1:1, 5:1 and 10:1. The result showed that the superior biomass productivity was facilitated at a C/N ratio of 5:1 (106 mg L-1 d-1), and the high degradation rate constants (kCOD = 0.25 d-1, kTN = 0.29 d-1, kTP = 0.35 d-1) was approximated using a first-order kinetic model. The removal of pollutants was remarkably high, exceeding 90% (COD), 93% (TN), and 96% (TP). Nevertheless, the C/N ratio of 1:1 resulted in a threefold drop in biomass-specific growth rate (µ = 0.07 d-1). Microalgal assimilation, followed by bacterial denitrification, is the major pathway of removing total nitrogen when the C/N ratio exceeds 5:1. Activated sludge plays an important role in improving microalgae tolerance to high concentration of ammonia nitrogen and boosting nitrification (light phase) and denitrification (dark phase). The use of phycosphere associated bacteria could be a promising strategy for controlling nutrients pollution and other environmental considerations in wastewater.

Comparison of degradation kinetics of tannery wastewater treatment using a nonlinear model by salt-tolerant Nitrosomonas sp. and Nitrobacter sp.

Conventional biological treatment has been reported to be ineffective for pollutant removal in tannery wastewater due to high salinity. To overcome it, this work used salt-tolerant bacteria (STB) isolated from a membrane bioreactor to evaluate the organic and nutrient removal through a series of batch experiments. Compared with the control, the STB reactor enhanced the reduction of persistent organics by 11% based on the double exponential decay model. Besides, the removal of NH4+-N is 26% higher, satisfying the first-order decay model. The nitrification was inhibited entirely in control during 48 h, whilst the assimilation process involved 55% of total nitrogen removal. In the STB reactor, nitrification occurred after 12 h, resulting in significantly increased NO2--N and NO3--N concentrations according to the logistic function. Although nitrification was successfully activated, C/N ratios and free ammonia were identified as limiting factors for STB activity, requiring mitigation strategies in further studies.