Journal of Environmental Engineering

The use of aquatic plants has recently become a popular technique for ecological restoration and purification of eutrophic rivers and lakes. In this paper, various technologies were studied and designed against the background of research and demonstration projects for pollution control in Dianchi Lake and comprehensive improvement of water quality. Different technical units were designed in the horizontal and vertical spaces of the water body. Horizontal spaces included plant buffers on the surface, algae enrichment and diversion, innovative floating beds, and emerging plant zones at the shoreline. Vertical spaces include ecological floating beds, ecological jellyfish, and ecological membrane coverings. Spatial growth patterns of aquatic plants were constructed with rational use of water space and integration with various techniques to maximize the absorption of nutrients in the lake, increase the transparency of the water, and alleviate lake eutrophication. The previous technologies were combined, and technical demonstrations were conducted using experiments. We set up an integrated technical demonstration district with an area of $0.25{\mathrm{km}}^2$ on the north shore of Dianchi Lake, and the results demonstrated the following: water transparency increased by $>50\mathrm{cm}$; algae biomass decreased by $>70\%$; and the percent removal of total phosphorous (TP), total nitrogen (TN), and chemical oxygen demand (${\mathrm{COD}}_{\mathrm{Mn}}$) was $>30\%$.

India has drawn the world’s attention due to the high-paced growth of industrialization, urbanization, and population. However, another aspect of higher economic development has resulted in increased waste generation and consumption of natural resources, and hence ecological degradation and pollution. As awareness increases of the detrimental effects of currently used waste disposal methods on the environment, accountability is needed for an effective waste management system. This paper presents the existing situation of municipal solid waste (MSW) generation, composition, management, and problems associated with it in Indian cities. Statistically, urban India produced around 62 Mt of solid waste ($450\mathrm{g}/\mathrm{capita}/\mathrm{day}$) in 2015. Approximately 82% of MSW was collected and the remaining 18% was litter. The waste treated was only 28% of the collected waste, and the remaining 72% was openly dumped. Waste collection efficiency ranges between 70% and 95% in major metropolitan cities, whereas in several smaller cities it is below 50%. Most urban local bodies (ULBs) are unable to manage such a large amount of solid waste due to financial debilities and inadequate infrastructure. Source segregation of waste, doorstep collection, options for recycling and reuse, technologies for treatment, land availability, and disposal competence are a few of the prime challenges. Addressing these challenges, this paper discusses the current government’s policies, financial supports, and incentives for solid waste management (SWM), as well as gaps and suggestions of current SWM rules. This paper also addresses a comparative view of MSW management in different countries and adoption of waste processing technologies for a particular place in India. This study can assist decision makers, planners, municipal authorities and researchers to create a more efficient plan for the current status of, challenges of, and barriers to SWM in India.

Water flushing increases the urine transportation cost in a source-separation system, a new concept in sustainable management of municipal wastewater. This study investigates the reduction of water and the reconcentrations of nutrients from hydrolyzed urine via direct-contact membrane distillation (DCMD), especially addressing the loss of ammonia. High rejections of phosphate and K were achieved ($>97\%$) when hydrolyzed urine was concentrated by 17.8 times. However, total ammonia in the permeate increased to $11.0\mathrm{g}\mathrm{N}{\mathrm{L}}^{-1}$, resulting in a low rejection (31%) of total ammonia and reducing the quality of water generated. Many factors, including temperature difference, urine dilution ratio, urine pH, urea hydrolysis, and urine stabilization via nitritation, were investigated, aiming to minimize the ammonia loss. Full nitritation of urine induced low pH and reduced the concentrations of total ammonia and chemical oxygen demand. Accordingly, the rejection of total ammonia reached 94% in the concentrated urine, and solutes in the permeate water were significantly reduced. Therefore, biological stabilization of urine prior to the DCMD process is recommended for minimizing the ammonia loss and improving the quality of permeate water generated.

Engineered struvite precipitation (ESP) is now a common procedure to recover phosphorus and nitrogen from waste streams such as wastewater-treatment-plant sidestreams, urine, landfill leachate, and agricultural waste. Depending on the waste stream, the liquid effluent from ESP is likely to still contain either nitrogen or phosphorus. In the case of wastewater-treatment-plant sidestreams, the liquid recycled back to the head of the plant still contains high concentrations of nitrogen, which can cause instability in mainstream treatment processes and additional energy and chemical costs. Therefore, a need exists to remove the nitrogen before it reaches the mainstream. For this research, nitrogen removal and energy recovery from the effluent of ESP were achieved using a proof-of-concept fixed-film nitrification and microbial fuel cell (MFC) process. Fixed-film nitrification and MFC together removed 52% of nitrogen from the liquid effluent of ESP, while the MFC generated 0.3-mW power per ${\mathrm{m}}^2$ of anodic surface area. This process was not energy neutral, as energy input for aeration was greater than the energy output from the MFC. However, the goal of energy neutrality may be advanced beyond this proof-of-concept study by reducing the energy input for aeration and increasing energy output through further improvement of MFC performance. This is the first study to demonstrate how fixed-film nitrification and MFCs can be used to treat the liquid effluent from ESP to recover energy and remove nitrogen, while simultaneously reducing the undesirable recycling of nutrients from sidestreams back to mainstream treatment. The process is aimed to transform wastewater-treatment plants into resource recovery facilities of the future, and to reduce operational costs through nutrient removal, energy generation, and decreased nutrient load to mainstream treatment.

This study applies calculations and methodologies for the evaluation of concentrations of zinc and nickel coupled to local reference values (background). It also calculates the geoaccumulation index and the intensity of the contamination of the metals according to the deterministic classes established by current standards which set the general guidelines and minimum procedures for the evaluation of material to be dredged in Brazilian jurisdictional waters. These goals are achieved through sampling of sedimentary profiles (core sampling) deposited over the years in the Mãe d’Água reservoir. The results show that the concentrations of zinc and nickel in the samples were above the local background values with growth and enrichment patterns. The results of the geoaccumulation index and current standards indicate that the bottom sediments have pollutant indicators, showing that the existence of sediment enrichment from these metallic elements is probably due to local urbanization activities.

Bromide concentrations have been changing in rivers in Pennsylvania. Elevated bromide in source waters at drinking water treatment plant intake locations is expected to increase the formation and bromine incorporation of disinfection by-products (DBPs) that present health risks to consumers. Results from major drinking water distribution systems in southwestern and southeastern Pennsylvania taken during a national sampling effort (1997–1998) were compared with more recent data from these same systems (2012–2016). Sample sets were compared both temporally, across the nearly 20-year span between the first and final sampling periods, and spatially, comparing southwestern and southeastern Pennsylvania. Total trihalomethanes (TTHM) and bromine incorporation data show little change in southeastern Pennsylvania. In southwestern Pennsylvania, TTHM decreased significantly, likely as a result of treatment modifications designed to comply with more stringent regulations. However, fractional bromine incorporation in THMs increased, indicating TTHM reductions were associated with reduced chloroform alone. Risk metrics prioritizing brominated species indicated no change in southwestern Pennsylvania despite the decline in the surrogate, TTHM, which is used for regulatory compliance.

Municipal solid waste incineration (MSWI) fly ash is internationally categorized into a hazardous waste due to its high content of heavy metals (HMs) and dioxins. A traditional electrochemical platform was intrinsically modified by changing stackings of samples in the electrolyzer to solve a near-anode concentration focusing (NA-CF) phenomenon during the electrokinetic remediation (EKR) and to improve electrokinetic performance to the HM removals from MSWI fly ashes. The effect of sample stacking in the electrolyzer on the removal performance of the electrokinetics was comprehensively investigated. Summarily, the stacking styles profoundly affected the electrochemical environment. The excavation of specimen near the anode chamber facilitated the diffusion of ${\mathrm{H}}^{+}$ ions in the electrolyte and effectively avoided the generation of NA-CF phenomenon. The best removal efficiencies for all four HM elements were achieved through simultaneously moving the ash samples out near the two electrodes. The influence of voltage gradient ($\mathrm{V}/\mathrm{cm}$) on the HM removals was proved to be more significant than the remediation time. The voltage gradient of $1.5–2.0\mathrm{V}/\mathrm{cm}$ and the remediation time of 18–21 days were determined as the optimal ranges for the remediation of MSWI fly ashes. The environmental toxicities of HMs were noticeably decreased using the adjusted EKR system. The average leaching toxicities of Zn, Pb, Cu, and Cd were reduced by approximately 60%, 83%, 58%, and 77%, respectively. The SD-EKR process significantly reduced the environmental activity of MSWI fly ashes. The excavation of samples from subregions of S2 and S5 at the third day of EKR process increased HM dissolution, decreased ion-migration resistances, and facilitated HM removals from fly ashes.

Sludge bulking caused by filamentous microorganisms is one of the prevailing operational problems in activated sludge process. Its severity is determined by the relative abundance of filamentous microorganisms that prevents the close packing of sludge flocs. This occurrence interferes in the separation and settling activities leading to the failure of the overall treatment process. The severity of bulking has directed to numerous inhibition approaches. However, the approaches have various drawbacks such as high sludge wastage. Hence, operation of a biological reactor by a static magnetic field was attempted. Two sequencing batch reactors (SBR), Reactor A (${\mathrm{SBR}}_{\mathrm{A}}$) and Reactor B (${\mathrm{SBR}}_{\mathrm{B}}$), were operated in low dissolved oxygen level to encourage filamentous microorganisms’ growth. ${\mathrm{SBR}}_{\mathrm{A}}$ was subjected to a magnetic field intensity of 88.0 mT, while ${\mathrm{SBR}}_{\mathrm{B}}$ served as the control system. The findings showed that sludge flocs in ${\mathrm{SBR}}_{\mathrm{A}}$ were positively developed, corresponding to a lower sludge volume index (SVI) of less than $10\mathrm{mL}/\mathrm{g}$. Magnetically exposed activated sludge also showed less possibility on the presence of filamentous microorganisms compared with unexposed sludge. These evidences confirmed that use of magnetic field is feasible to inhibit filamentous sludge bulking occurrence.

Photocatalysis has been proposed as a synergistic addition to ultraviolet (UV) dosing systems to provide a form of advanced oxidation. The photocatalytic process, however, is significantly inhibited by dissolved organic matter (DOM). Membrane bioreactors (MBRs) offer an opportunity to simultaneously control DOM and provide a structure to support photocatalysts. Here, effluent organic matter (EfOM) samples from two MBR facilities employing membranes with different nominal pore sizes were assessed for their inhibition of ${\mathrm{TiO}}_2$ photocatalysis. Photocatalytic activity was quantified by measuring the photodegradation of a probe compound, para-chlorobenzoic acid. Analysis of inhibition profiles of both EfOM and a well-known $·\mathrm{OH}$ quencher, tert-butyl alcohol ($t$-BuOH) showed that MBR EfOM inhibited photocatalysis via competitive adsorption and surface reactions as well as reactions in the bulk phase. EfOM concentrations below $0.34\mathrm{mgC}/\mathrm{L}$ did not inhibit photocatalysis, whereas EfOM concentrations of above $1.8\mathrm{mgC}/\mathrm{L}$ completely negated photocatalytic action. The results suggest that avoiding unwanted quenching reactions may be possible with proper operational control of the upstream MBR process. Insights into the relevance of radical quenching mechanisms are offered with regard to applying ${\mathrm{TiO}}_2$ to wastewater treatment.