Current Environmental Engineering - Volume 6, Issue 1, 2019

Per capita average annual freshwater availability is gradually reduced due to increasing population, urbanization and affluent lifestyles. Hence, management of wastewater is of great concern. The wastewater from different industries can be treated by various conventional treatment methods but these conventional treatment technologies seem to be ineffective for the complete removal of pollutants especially refractory organic compounds that are not readily biodegradable in nature. Detergents, detergent additives, sequestering agents like EDTA, Pesticides, Polycyclic aromatic hydrocarbons, etc. are some of the recalcitrant organic compounds found in the wastewater. One of the treatment technologies for the removal of recalcitrant organic compounds is Advanced Oxidation Process (AOP). The production of hydroxyl free radical is the main mechanism for the AOP. AOP is a promising technology for the treatment of refractory organic compounds due to its low oxidation selectivity and high reactivity of the radical. Hydrogen peroxide (H2O2), Ozonation, Ultra-violet (UV) radiation, H2O2/UV process and Fenton’s reaction are extensively used for the removal of refractory organic compounds thus reducing Chemical Oxygen Demand (COD), Total Organic Carbon (TOC), phenolic compounds, dyes etc. to great extent. From the studies, we found that Fenton’s reagents appear to be most economically practical AOP systems for almost all industries with respect to high pollutant removal efficiency and it is also economical. From the energy point of view, the ozone based process proves to be more efficient but it is costlier than the Fenton’s process.

Background: A new generation of the sustainable landfill is designed to achieve sustainable Municipal Solid Waste (MSW) management. It is hybrid anaerobic/aerobic biodegradation landfill followed by landfill mining. However, there is limited information on landfill mining, especially the criteria and process for the practitioner to determine the end of the landfill biodegradation to commence landfill mining. Objective: Hence the overall objective of this research was to develop a comprehensive resource mining plan for bioreactor landfills. Method: When waste decomposition becomes slower or stopped, the landfill can be mined to recover resources and utilize the recovered space. The amount of the gas generated, landfill temperature and landfill settlement are indirect measures of landfill activity. Also, the concentration of cellulose (C), hemicelluloses (H), and lignin (L) can describe the biodegradable fractions of waste. Hence the biodegradation in landfills can be monitored by recording the change in methane production, temperature, settlement and the (C+H)/L ratio of waste. Once methane recovery is minimal, landfill reaches a maximum settlement and, ambient temperature plus the (C+H)/L value reaches a stable value of 0.25 indicating end of biodegradation. At this point landfill resources including compost material, non-recoverable waste, and recyclables such as plastics, metal and glass can be mined and recovered. Compost and recyclables can be sold at market value and the non-recovered waste with high energy content can be used as refuse-derived fuel. Once the landfill has been mined space can be reused thus eliminating the need to allocate valuable land for new landfills. Result: The landfill mining detailed in this manuscript utilizes principles from single stream type recycling facilities to ensure feasibility. The first landfill will be excavated and screened to separate the biodegraded soil and compost fraction from the recyclables. Then the screened recyclable materials are transported for further processing in a single stream type separation facility where they will be separated, bundled and sold. Conclusion: A cost calculation was performed for the resource mining of Calgary Biocell and if the mined resources are sold at market values, then the mining of Calgary Biocell would generate approximately $4M.

Background: Trees often affect the chemical properties of soil, positively or negatively. Objective: This paper studied the effects of Podocarpus falcatus and Markhamia lutea trees on soil chemistry in Ruhande Arboretum, Rwanda. Methods: Soil samples were collected using Zigzag method from Arboretum forest of Ruhande at different depths (0-20, 20-40 and 40-60 cm). For each plot, 25 samples were collected to make one composite sample per plot for each depth. Results: The results showed that tree species contributed to the changes of soil chemistry along the depths of the soil layers. The laboratory analyses showed that there was a high significant influence of tree species on soil pH and Aluminum ions. However, it was observed that there was no significant influence of Podocarpus falcatus and Markhamia lutea species on the available phosphorus or on the total exchangeable acidity. On the other hand, analyzing soil samples under Markhamia lutea showed an increase in the total nitrogen and a decrease in the pH and available phosphorus. Conclusion: Trees affect the chemical properties of soils. Therefore, it is recommended that under acidic soils, for example, forestry and agroforestry actors should use less acidifying tree species, such as Markhamia lutea and Podocarpus falcatus.

Background: Wet coffee processing consists of the removal of the pulp and mucilage of the coffee cherry. This process generates a large amount of acidic wastewater which is very aggressive to the environment because of its high content of recalcitrant organic matter. Therefore, treatment is necessary before discharge to water bodies. Because of this reason, this study aimed to evaluate the organic matter removal efficiency in an Anaerobic Baffled Bioreactor (ABR) coupled to a Microfiltration Membrane (MF) system as a new eco-friendly option in the treatment of wet Coffee Processing Wastewater (CPWW). Methods: Two systems (S1 and S2) were evaluated at Hydraulic Retention Times (HRT) of 59 h and 83 h, respectively. Both systems were operated at mesophilic conditions, at a Transmembrane Pressure (TMP) of 50 kPa during 1800 h. Results: The S2 generated higher organic matter removal efficiency, reaching removal values of turbidity of 98.7%, Chemical Oxygen Demand (COD) of 81%, Total Solids (TS) of 72.6%, Total Suspended Solids (TSS) of 100%, and Total Dissolved Solids (TDS) of 61%, compared with the S1. Conclusion: The S2 represents a new eco-friendly alternative to treat CPWW and reduce its pollutant effect.

Background: Green Infrastructure (GI) is widely being promoted as an adaptation strategy for urban flooding. Like urban flooding, tree species could be impacted by future climatic conditions. However, there have been limited studies on the implications of future climate on GI planning, mostly due to the lack of climate data at higher spatial resolutions. Objective: In this paper, we analyze the implications of climate projections on heat hardiness zones since this could impact the GI landscape in the coming years. This is an extension of our earlier work on evaluating impacts of climate projections on plant hardiness zones. Method: Using downscaled daily temperature data from ten Coupled Model Intercomparison Project Phase 5 (CMIP5) climate models for the historical (1980 - 2005) and projected (2025 - 2050) periods, we analyzed future heat hardiness zones in the watershed bounding Knox County, TN. We analyzed the implications of these outputs for the current list of suggested native and non-native tree species selected for GI in the study area. Results: All the models suggest that a considerable part of the study area will move into the next warmer heat zone. While most trees remain suitable for GI, several are at the limit of their ideal heat zones. Conclusion: The insights from this study will help guide the selection and placement of GI across the study area. Specifically, it should help green infrastructure planners design better mitigation and adaptation strategies to achieve higher returns on investments as more cities are now investing in GI projects.

Background: Multi-hazard risk assessment has long been centered on small scale needs, whereby a single community or group of communities’ exposures are assessed to determine potential mitigation strategies. While this approach has advanced the understanding of hazard interactions, it is limiting on larger scales or when significantly different hazard types are present. In order to address some of these issues, an approach is developed where multiple hazards coalesce with losses into an index representing the risk landscape. Methods: Exposures are assessed as a proportion of land-area, allowing for multiple hazards to be combined in a single calculation. Risk calculations are weighted by land-use types (built, dual-benefit, natural) in each county. This allows for a more detailed analysis of land impacts and removes some of the bias introduced by monetary losses in heavily urbanized counties. Results: The results of the quantitative analysis show a landscape where the risk to natural systems is high and the western United States is exposed to a bulk of the risk. Land-use and temporal profiles exemplify a dynamic risk-scape. Conclusion: The calculation of risk is meant to inform community decisions based on the unique set of hazards in that area over time.