Ecological Wastewater Treatment System Research Articles

Impacts of polymethyl methacrylate nanoplastics on nutrient removal, microbial community and antibiotic resistant genes in bioretention systems amended with biochar and pyrolusite

Increasing release of nanoplastics (NPs) into wastewater may pose a potential threat to nitrogen and phosphorous removals in ecological wastewater treatment systems. To better understand the responses of bioretention system (BRS) by NPs, a Conventional Sand BRS (CB-BRS) and two modified BRSs, Microbial Fuel Cell (MFC)-Biochar BRS (MB-BRS) and Pyrolusite-MFC-Biochar BRS (PMB-BRS) were established and the effects of 0.5 mg/L polymethyl methacrylate (PMMA) NPs on nutrient removal, microbial community structures, as well as key enzyme activities, functional genes, antibiotic resistance genes (ARGs) were comprehensively investigated within a 120-day exposure. We observed a significant decrease in total nitrogen (TN) and total phosphorous (TP) removals in BRSs. TN removal efficiencies gradually declined from 93.56 % to 54.23 % and the TP removal efficiencies declined from 88.29 % to 74.47 % in CB-BRS. By contrast, MB-BRS (TN:72.28 %; TP:81.58 %) and PMB-BRS (TN:80.76 %; TP:96.69 %) apparently overperformed CB-BRS. In conjunction with ecological-relevant functional prediction based on the FAPROTAX database, the Illumina high-throughput sequencing unveiled substantial selective pressure imposed by PMMA NPs, particularly leading to diminished denitrifying microbes. PMMA NPs adversely affected key nitrogen-transformation enzyme activities (URE, AMO, and NIR) and denitrification functional genes (nirK, nirS, and nosZ). Alarmingly, PMMA NPs stimulated ARGs (sulI and tetC) propagation in all BRSs. Notably, the introduction of pyrolusite and biochar mitigated the adverse effects through the formation of manganese cycle and prosperous electron transfer process and effectively retained ARGs after 120-day exposure. The findings provide unprecedented insights into the potential ecological threat posed by PMMA NPs and viable strategies to control this hidden danger.

Ecological Wastewater Treatment System in a School Environment Using a Horizontal Flow Biological Reactor: The Case of Typha

Ecological Wastewater Treatment System in a School Environment Using a Horizontal Flow Biological Reactor: The Case of Typha

Ecological Wastewater Treatment System Using a Horizontal Flow Biological Reactor: The Case of Vetiver

Ecological Wastewater Treatment System Using a Horizontal Flow Biological Reactor: The Case of Vetiver

Design and Sizing of an Ecological Wastewater Treatment System in a School Environment: A Case Study of Ndiebene Gandiol 1 School

Design and Sizing of an Ecological Wastewater Treatment System in a School Environment: A Case Study of Ndiebene Gandiol 1 School

Simulating and predicting the performance of a horizontal subsurface flow constructed wetland using a fully connected neural network

Constructed wetland systems, as an engineered ecological system, are being increasingly employed for wastewater treatment. However, owing to the complex incentives for pollutant removal in ecological treatment systems, it is challenging to simulate and optimize the operation of constructed wetlands to advance ecological wastewater treatment systems. In this study, a horizontal subsurface flow constructed wetland (HSCW) system was constructed and applied to a rural wastewater treatment system. Reeds (Phragmites australis) were planted in the HSCW to remove pollutants from the wastewater. Further, a fully connected neural network (FCNN) was designed based on the Adam optimization algorithm with weather conditions, quality, and quantity of influent and effluent as input to simulate and predict the performance of the HSCW. The results of the FCNN simulation analysis showed that the relative errors of the simulated concentrations of CODcr, NH4+-N, total nitrogen (TN), and total phosphorus (TP) for the FCNN model were 8.07 ± 10.73%, 18.34 ± 17.75%, 9.90 ± 11.91%, and 9.47 ± 10.98%, respectively. The mean absolute errors (MAEs) of CODcr, NH4+-N, TN, and TP for the FCNN model were 2.17, 1.06, 1.21, and 0.54, respectively. The root-mean-squared errors (RMSEs) of CODcr, NH4+-N, TN, and TP for the FCNN model were 3.91, 2.05, 2.22, and 0.80, respectively. The correlation coefficients (R2) of CODcr, NH4+-N, TN, and TP for the model were 0.99, 0.91, 0.92, and 0.82, respectively. These results indicate that the model performed well. Sensitivity analysis results also showed that temperature, solar radiation intensity, and rainfall had a strong impact on the model accuracy. This study verifies that an artificial neural network can effectively reflect the nonlinear function of each factor and is suitable for simulating HSCW treatment for wastewater under various conditions, providing a new optimization method for wastewater ecological treatment systems.

Ecological wastewater treatment system: Management approach to solve sanitation and water problems

Wastewater contains various types of pollutants, such as nutrients, solids, organic carbon, metals, inorganic salts, pathogens, etc. Therefore, effective wastewater treatment is crucial for public health as well as for environmental concern. On the other hand, water management with limited water resources is a great challenge in most countries. The freshwater shortage is seriously affecting the economic and social growth of developing nations. An ecological wastewater treatment system is a concept towards ecologically and economically sounds wastewater management. Water and organic nutrients in wastewater consider as a resource and can reuse and recycle in agriculture. The study reviewed the principles and concepts of the ecological wastewater treatment system and a case study of the ecological treatment system by growing economic vegetation. A hybrid constructed wetland (CW) system was used to investigate the performance. The CW system showed high removal efficiency for TP (total phosphorus), NH4 (ammonium), and TN (total nitrogen). The removal efficiencies were 97%, 75%, and 64% for TP, NH4-N, and TN, respectively. Ecological wastewater treatment system is cost-effective, and energy-saving also offers nutrients recycling, water reuse, recreation activities, and vegetation growth.

Coupling ecological wastewater treatment with the production of livestock feed and irrigation water provides net benefits to human health and the environment: A life cycle assessment

Ecologically designed wastewater treatment systems (ex., Eco-Machines™) utilize a diverse ecosystem to treat wastewater to the same extent as conventional treatment, but require less energy and chemical inputs. The environmental benefits of Eco-Machines™ can be theoretically maximized by incorporating hyperaccumulating aquatic plants (ex., duckweed) to facilitate nutrient recovery and conversion into protein-rich biomass, which can then be harvested for a range of agricultural and bioenergy applications. Although it has been established that ecological wastewater treatment systems are more cost- and energy-efficient than conventional wastewater treatment systems, a systematic life cycle assessment (LCA) of an Eco-Machine™ coupled with its beneficial by-products has not been conducted. In this study, a series of LCAs were performed on different operational scenarios for a 1000 gallon per day, pilot-scale Eco-Machine™ that, in addition to producing irrigation-quality water, also produces duckweed biomass for aquaculture. The analysis revealed that Eco-Machines™ located in warm climates, which do not require a greenhouse or supplemental heating, use approximately a third of the energy and produce half of the greenhouse gas emissions compared to conventional wastewater treatment systems in similar locations, while also providing benefits to human health, ecosystem quality, climate change, and resources. In addition, increasing the growth area for duckweed using vertical farming techniques improves the overall impact of the system. This study suggests that with proper management, ecological wastewater treatment systems that upcycle nutrients and water into beneficial products can provide a net benefit to human health and the environment.

Whole-Genome Sequences of Salmonella Isolates from an Ecological Wastewater Treatment System

Twenty-seven Salmonella isolates were collected from four locations within an ecological wastewater treatment system located at The Pennsylvania State University and were subjected to whole-genome sequencing. The sequences obtained were used for in silico characterization, including serotyping and phylogenetic relatedness analysis.

A beneficial by-product of ecological wastewater treatment: An evaluation of wastewater-grown duckweed as a protein supplement for sustainable agriculture

Ecological wastewater treatment systems that incorporate aquatic plants (like duckweed) have the potential to recover nutrients and produce high-quality protein, simultaneously alleviating two global issues: hunger and lack of sanitation. Although protein production by duckweed in simple lagoon systems and laboratory trials has been reported, its physiology throughout more complex wastewater treatment systems containing a range of different environmental conditions has not been examined. In this study, a duckweed co-culture (Lemna japonica/minor and Wolffia columbiana) was grown on wastewater from four different stages of a pilot-scale ecological treatment system. Contrary to the literature, the protein content of duckweed did not consistently increase with increasing aqueous nitrogen concentrations, but rather appeared to also be dependent on chemical and microbial interactions. This study indicates that with proper management, duckweed grown in ecological wastewater systems can sustainably produce protein at rates exceeding those of common land-grown forage crops (10.1 ton ha−1 yr−1).

Feasibility study of ecological wastewater treatment system for decentralized rural community in South Korea

The natural and ecological wastewater treatment system (NEWS) was developed to target organic pollutants and nutrients for decentralized rural communities. The system was installed in Sangwang-dong, Gongju-si, Chungcheongnam-do, South Korea, and operated for about nine months. It consisted of three parts: the anaerobic septic tank, the absorbent-biofilter system (ABS), and the up- and down-flow constructed wetland. The respective nitrogen (N), phosphorus (P), and chemical oxygen demand removal rates of the NEWS were 45.94, 48.65, and 98.47% in the growing season and 27.93, 23.78, and 86.45% in the winter season. The significantly low N and P removal rates could have been caused by microorganism vitality in the ABS, as most of the nutrients occurred in an organic form. Average water temperature of the ABS was 18.13°C in the growing season and 8.289°C in the winter season, which might have influenced the low overall removal rate during the winter season. Performance of the NEWS was efficient, independent of the influent concentration within the study period, except a short term clogging. Considering its high performance, low maintenance, and cost-effectiveness, the NEWS is an effective, feasible alternative for sewage treatment in decentralized communities in South Korea.

The Effect of the Hydraulic Retention Time on the Performance of an Ecological Wastewater Treatment System: An Anaerobic Filter with a Constructed Wetland

This work assesses the performance of a municipal pilot wastewater treatment system employing an up-flow anaerobic filter (UAF) followed by a horizontal subsurface constructed wetland (HSSCW). This pilot scale demonstration project was implemented in a zone with subtropical climate in order to protect Lake Chapala from wastewater loads that are discharged by small communities in the Lake’s vicinity. The filters were filled with tezontle as the media for biofilm support and the HSSCW was planted with two ornamental plants species, Canna hybrids and Strelitzia reginae. The experiment evaluated three hydraulic retention times (HRT) of 18, 28 and 38 h in the UAF, which corresponds to two, three and four days in HSSCW over 66 weeks. The mean efficiencies found for the complete system were 80% and 90% of BOD, 80% and 86% of COD, 30% and 33% of Ntot and between 24% and 44% of Ptot. It was possible to remove almost 80% of organic matter in 18 h in the UAF while the HSSCW reached 30% of removal for Ntot in a HRT of three days. As expected, the UAF was responsible for removing most of the organic matter and the HSSCW removed most of the nitrogen.

Comparative Study of Three Two-Stage Hybrid Ecological Wastewater Treatment Systems for Producing High Nutrient, Reclaimed Water for Irrigation Reuse in Developing Countries

In this study, three different two-stage hybrid ecological wastewater treatment systems (HEWTS) with combinations of horizontal flow (HF) constructed wetlands (CWs), vertical flow (VF) CWs and stabilization ponds (SP) were evaluated for the removal of Organic-N, NH4+, NO3−, Total N, Total P, Total Coliforms (TCol) and Escherichia Coli, BOD, COD and TSS. The overall goal of the study was novel in comparison to most other studies in that we sought to evaluate and compare the efficiency of the three HEWTSs for water quality improvements, while minimizing nutrient removal from the wastewater in order to generate high quality reclaimed water for reuse for irrigation of crops. The most effective systems were those systems containing a vertical flow component, either HF-VF or VF-HF. In these two HEWTS, NH4+ was reduced by 85.5% and 85.0% respectively, while NO3− was increased to 91.4 ± 17.6 mg/L and to 82.5 ± 17.2 mg/L, respectively, an artifact of nitrification. At the same time, E. coli was reduced by 99.93% and 99.99%, respectively. While the goal of most wastewater treatment is focused on reducing nutrients, the results here demonstrate that two-stage HEWTSs containing VF components can be used to produce a high quality effluent while retaining inorganic nutrients, thereby conserving this valuable resource for reuse as irrigation water for agriculture in subtropical developing countries where water and fertilizer resources are scarce or expensive.

Optimized design of natural ecological wastewater treatment system based on water environment model of dynamic mesh technique

A Natural Ecological Wastewater Treatment System (NEWTS) is usually built on natural terrain with necessary topography modification to improve water flowing route and pattern, and then the topography modified NEWTS should also have a reasonable water storage volume and hydraulic retention time so as to achieve the anticipated water purification effect. In this study, the dynamic mesh technique based on the finite element method and element storativity coefficients was presented to develop a two-dimensional hydrodynamic and water quality model, which was used to optimize the design of NEWTS under the dynamic land-water boundary due to various water storage volume. The models were employed in the optimized design of NEWTS from a large abandoned coal mine, which purifies the polluted water flowing into a large water storage lake, as part of the East Route South-to-North Water Transfer Project in China. Specifically, the natural topography modification scheme was presented, and further, a reasonable water storage volume and hydraulic residence time was obtained, based on the reasonable estimation of roughness coefficient and pollutant removal rate of the NEWTS with phragmites communis.

Development of natural and ecological wastewater treatment system for decentralized community in Korea

A pilot study of the natural and ecological wastewater treatment system (NEWS) was performed to treat sewage in decentralized small rural communities in Korea. The absorbent-biofilter system (ABS) provided secondary level pretreatment and demonstrated high removal efficiency especially for SS and BOD5 showing 88.5 and 82.9%, respectively. The influent and effluent concentrations of TN were 42.1 and 26.2 mg L−1, respectively, with the removal efficiency of 37.8%. In case of TP, the removal efficiency was 45.1% with the influent and effluent concentrations of 3.1 and 1.7 mg L−1. The ABS effluent could not meet the effluent standards, and the further treatment was required. The subsequent up- and down-flow constructed wetland (UDCW) provided further polishing of the ABS effluent and demonstrated effective removal of nutrients as well as SS and BOD5 with over 70% removal rates. Overall performance of the NEWS, which was composed of ABS and UDCW, demonstrated remarkably high removal rates for BOD5 (>95.7%), SS (>97.5%), TN (>91.8%) and TP (>90.1%) and met all the effluent standards stably independent of temperature and influent loading in the experimental range. The UDCW used light and porous granular substrate (∅ 5–10 mm, specific gravity of 1.2) with large surface area, and clogging problem was not observed during the study period. The system was cost effective and required minimal maintenance and negligible amount of electricity, and problems associated with noise, odor, files, and sludge were not observed. Considering characteristics of decentralized wastewater treatment systems, the NEWS system was found to be a practical alternative and its application is recommended up to 300 m3 day−1. The NEWS system has an economic problem above 300 m3 day−1, because of complicated equipment, higher operation costs, and maintenance specialists. The NEWS system was coast effective and required minimal maintenance and negligible amount of electricity, and problems associated with noise, odor, files, and sludge were not observed.

Industrial By-Products and Natural Substrata as Phosphorus Sorbents

The efficiency of phosphorus (P) removal in ecologically-engineered wastewater treatment facilities, such as artificial wetlands and sand filters, can be improved by using a reactive sorbent. The sorbent must therefore have a high P-sorption capacity and an adequate hydraulic conductivity. Several filter materials have been tested here in regard to their P-sorption capacity. In this study, three natural materials — opoka (a bedrock found in south-eastern Poland) limestone and the B horizon of a forest soil, plus two artificial materials — blast furnace slag (crystalline and amorphous, in two particle sizes (0–0.125 mm and 0.25–4 mm), and fly ash were investigated. Phosphate sorption and isotherm studies were performed. In addition, physical and chemical properties of the materials were also investigated. The P-sorption experiment showed that all materials were capable of sorbing P to various extents. The coarse crystalline slag had the highest P-sorption capacity followed in order by the fine crystalline slag, the fine amorphous slag, the B horizon, the limestone, the coarse amorphous slag, the ash and the opoka. The isotherm studies showed that the B horizon was the most efficient P retainer, followed in order by the coarse crystalline slag, the fine crystalline slag, the fine amorphous slag and the coarse amorphous slag, with opoka and limestone showing the poorest retention. It was concluded that the crystalline slags had the highest P-sorption capacities, and that coarse crystalline slag possessed the highest hydraulic conductivity, suggesting that this material is the most suitable for use in ecological wastewater treatment systems.