Performance of high-rate constructed phytoremediation process with attached growth for domestic wastewater treatment: effect of high TDS and Cu

Metagenomics and metatranscriptomics suggest pathways of 3-chloroaniline degradation in wastewater reactors

Biological wastewater treatment systems are often affected by shifts in influent quality, including the input of toxic chemicals. Yet the mechanisms underlying the adaptation of activated sludge process performance are rarely studied in a controlled and replicated experimental setting, particularly when challenged with a sustained toxin input. Three replicate bench-scale bioreactors were subjected to a chemical disturbance in the form of 3-chloroaniline (3-CA) over 132 days, after an acclimation period of 58 days, while three control reactors received no 3-CA input. Ammonia oxidation was initially affected by 3-CA. Within three weeks of the experiment, microbial communities in all three treatment reactors adapted to biologically degrade 3-CA resulting in partial ammonia oxidation recovery. Combining process and microbial community data from amplicon sequencing with potential functions gleaned from assembled metagenomics and metatranscriptomics data, two putative degradation pathways for 3-CA were identified. The first pathway, determined from metagenomics data, involves a benzoate dioxygenase and subsequent meta-cleavage of the aromatic ring. The second, determined from intensive short-term sampling for gene expression data in tandem with 3-CA degradation, involves a phenol monooxygenase followed by ortho-cleavage of the aromatic ring. The relative abundances of amplicon sequence variants associated with the genera Gemmatimonas, OLB8, and Taibaiella correlated significantly with 3-CA degradation. Metagenome-assembled genome data also showed the genus OLB8 to be differentially enriched in treatment reactors, making it a strong candidate as 3-CA degrader. Using replicated reactors, this study has demonstrated the impact of a sustained stress on the activated sludge process. The unique and novel features of this study include the identification of putative pathways and potential degraders of 3-CA using long-term and short-term sampling in tandem with multiple methods in a controlled and replicated experiment.

Membrane Water Treatment for Drinking Water Production from an Industrial Effluent Used in the Manufacturing of Food Additives

An integrated membrane process for treatment of effluents from food additive manufacturing was designed and evaluated on a laboratory scale. The principal focus was water recovery with the possibility of its reuse as potable water. The industrial effluent presented high content of dyes and salts. It was red in color and presented brine characteristics. The whole effluent was fed into the integrated process in continuous flow. The steps of the process are as follows: sedimentation (S), adsorption by activated carbon (AC), ion exchange using resins (IEXR), and reverse osmosis (RO) (S–AC–IEXR–RO). The effect of previous operations was evaluated by stress-rupture curves in packaged columns of AC and IEXR, membrane flux, and fouling dominance in RO. Fouling was evaluated by way of the Silt Density Index and membrane resistance examination during effluent treatment. The integrated membrane process provided reclaimed water with sufficiently high standards of quality for reuse as potable water. AC showed a high efficiency for color elimination, reaching its rupture point at 20 h and after 5L of effluent treatment. IEXR showed capacity for salt removal, providing 2.2–2.5 L of effluent treatment, reaching its rupture point at 11–15 h. As a result of these previous operations and operating conditions, the fouling of the RO membrane was alleviated, displaying high flux of water: 20–18 L/h/m² and maintaining reversible fouling dominance at a feed flow rate of 0.5–0.7 L/h. The characteristics of the reclaimed water showed drinking water standards

Nitrogen and phosphorus removal in simulated wastewater by two aquatic plants

Water pollution control is the focus of environmental pollution control. Ecological water treatment is widely used because of its low cost and landscape effect, and has no pollution. Aquatic plants have attracted wide attention because of their low cost and high level of resource utilization. In order to study the effects of emergent and submerged plants on the removal of different concentrations of wastewater, and the effect of pollutants on plant growth, two common aquatic plants found in Northeast China (Iris ensata Thunb. and Potamogeton malaianus Miq.) were selected. Under static conditions, the removal efficiency of nitrogen and phosphorus in wastewater with different concentrations by two kinds of plants was studied. The results showed that the removal rate of total nitrogen (TN) in medium- and high-pollutant concentration water samples and total phosphorus (TP) in medium- and low-pollutant concentration water with I. ensata reached more than 75%. The removal rate of TN in the medium-pollutant concentration water with P. malaianus reached 71.4%, while the removal efficiency of TN and TP in the low-pollutant concentration water was higher than 80%. In the Nanhu Park Lake samples, I. ensata had the highest removal rates of TN (80.38%) and TP (85.62%). This study shows that both I. ensata and P. malaianus can be used as aquatic plants to restore the water quality of urban lakes. This research provides an important basis for the phytoremediation and treatment of urban domestic wastewater and urban surface water bodies in Northern China.

Ecological treatment technology for agricultural non-point source pollution in remote rural areas of China

Agricultural non-point source pollution is one of the important reasons for rural water pollution, and it is also an important source of water eutrophication. In recent years, with the rapid economic growth and social changes in rural areas, large amounts of untreated domestic sewage and agricultural wastewater entering farmland require high efficiency, low operating costs, and minimal maintenance of treatment systems in rural and remote areas to minimize their impact on water and biodiversity. Since there is little research on the ecological treatment technology of agricultural non-point source pollution in China, from the perspective of controlling agricultural non-point source pollution, some ecological treatment technologies suitable for rural areas at home and abroad are summarized. This paper introduces the practical application of ecological treatment technology, the type of process, advantages and disadvantages, and the influencing factors of ecological treatment technology in the purification of sewage engineering and summarizes the removal mechanism of pollutants in ecological treatment technology. Eco-processing technologies are cost-effective in terms of their construction, maintenance, and energy needs and can be considered a sustainable wastewater treatment method, especially in remote areas and developing countries. It provides basic ideas for the construction of rural ecological treatment technology in China and puts forward suggestions and ideas for the future development trend of ecological treatment process sewage.

Efficiency of Five Selected Aquatic Plants in Phytoremediation of Aquaculture Wastewater

The lack of clean water sources, due to the presence of pollutants in water, is a major issue in many countries, including Malaysia. To overcome this problem, various methods have been introduced, including phytoremediation treatment. Therefore, this phytoremediation study examined the ability of five aquatic plants—Centella asiatica, Ipomoea aquatica, Salvinia molesta, Eichhornia crassipes, and Pistia stratiotes—to remove three pollutants—total suspended solids (TSS), ammoniacal nitrogen (NH3-N), and phosphate—from aquaculture wastewater. Using wastewater samples, each containing 50 g of one of the plants, the pollutant levels were measured every two days for 14 days. The results showed a drastic decline in the concentration of pollutants, where C. asiatica was able to remove 98% of NH3-N, 90% of TSS, and 64% of phosphate, while I. aquatica showed the potential to eliminate up to 73% of TSS and NH3-N, and 50% of phosphate. E. crassipes drastically removed 98% of phosphate, 96% of TSS, and 74% of NH3-N, while P. stratiotes was able to eliminate 98% of TSS, 78% of NH3-N, and 89% of phosphate. S. molesta was efficient in removing 89.3% of TSS and 88.6% of phosphate, but only removed 63.9% of NH3-N.

Desalination brine disposal methods and treatment technologies - A review

Brine, also known as concentrate, is the by-product of the desalination process that has an adverse impact on the environment due to its high salinity. Hence, viable and cost-effective brine management systems are needed to reduce environmental pollution. Currently, various disposal methods have been practiced, including surface water discharge, sewer discharge, deep-well injection, evaporation ponds and land application. However, these brine disposal methods are unsustainable and restricted by high capital costs and non-universal application. Nowadays, brine treatment is considered one of the most promising alternatives to brine disposal, since treatment results in the reduction of environmental pollution, minimization of waste volume and production of freshwater with high recovery. This review article evaluates current practices in brine management, including disposal methods and treatment technologies. Based upon the side-by-side comparison of technologies, a brine treatment technology framework is introduced to outline the Zero Liquid Discharge (ZLD) approach through high freshwater recovery and wastewater volume minimization. Furthermore, an overview of brine characteristics and its sources, as well as its negative impact on the environment is discussed. Finally, the paper highlights future research areas for brine treatment technologies aiming to enhance the effectiveness and viability of desalination.

Removal and monitoring acetaminophen-contaminated hospital wastewater by vertical flow constructed wetland and peroxidase enzymes

Hospital wastewater contains acetaminophen (ACT) and nutrient, which need adequate removal and monitoring to prevent impact to environment and community. This study developed a pilot scale vertical flow constructed wetland (CW) to (1) remove high-dose ACT and pollutants in hospital wastewater and (2) identify the correlation of peroxidase enzyme extruded by Scirpus validus and pollutants removal efficiency. By that correlation, a low-cost method to monitor pollutants removal was drawn. Plants, such as Scirpus validus, generated peroxidase enzymes to alleviate pollutants' stress. Results showed that the CW removed 3.5 to 6 logs of initial concentration 10 mg ACT/L to a recommended level for drinking water. The CW eliminated COD, TKN and TP efficiently, meeting the wastewater discharged standards of Thailand and Vietnam. By various multivariable regression models, concentrations of ACT in CW effluent and enzymes in S. validus exhibited a significant correlation (p < 0.01, R² = 68.3%). These findings suggested that (i) vertical flow CW could remove high-dose ACT and nutrient and (ii) peroxidase enzymes generated in S. validus, such as soluble and covalent ones, could track ACT removal efficiency. This would help to reduce facilities and analytical cost of micro-pollutants.

Cutting frequency effect on barium phytoextraction by macrophytes in flooded environment: A field trial

In anoxic environmental conditions and with a drastic reduction of the redox potential, the barium sulphate used in petroleum drilling fluids becomes a hazard to the ecosystem. A field study was conducted in Brazil in an area with a history of accidental Barium (Ba) contamination to evaluate the role of frequent plant cutting on phytoremediation. The plant species Typha domingensis and Eleocharis acutangula, cultivated in a combined plantation, were subjected to four different cut frequencies: every 90 days (four cuts), 120 days (three cuts), 180 days (two cuts), or 360 days (one cut). The total amount of Ba extracted from the soil by the plants was evaluated for each treatment and at different soil depths Overall, total Ba in the soil decreased the most dramatically for cut frequencies of 120 (37.83%) and 180 (47.73%) days at 0-0.2 m below the surface, and with cut frequencies of 120 (51.98%) and 360 (31.79%) at 0.2-0.4 m depth. Further, total Ba in the plant biomass was greatest in the 120 and 360-days frequency groups. Thus, cuts at intervals of 120 days or more are associated with high levels of Ba in the plant tissue and a decrease of soil Ba.

Constructed wetlands as sustainable ecotechnologies in decentralization practices: a review

Recently, a range of novel and cost-effective engineered wetland technologies for decentralization practices of domestic wastewater treatment have been developed with ecological process modification, the use of functionalized plants, and advanced biofilm formation. However, selecting the one that can be more appreciated for on-site sanitation is still uncertain. This paper reviews the role of plants, media materials, microorganisms, and oxygen transfer in domestic wastewater purification through constructed wetlands (CWs). The effectiveness of traditional and recently developed CWs and the necessity of an induced biofilm attachment surface (BAS) in these systems for the treatment of domestic sewage are presented. This review also elucidates the idea of CWs for domestic wastewater characteristics highly stressed by total dissolved solids and the adaptive strategies in mitigating the cold climate impacts on their efficiencies. Further research needed to enhance the stability and sustainability of CWs is highlighted. By a more advanced investigation, BAS CWs can be specified as an ideal treatment process in decentralization.