Potential Recovery Assessment of the Embodied Resources in Qatar’s Wastewater

Characterization of Ziziphus lotus’ Activated Carbon and Evaluation of Its Adsorption Potential

This study aims to prepare activated carbon from an interesting biomaterial, corresponding to the cores of Ziziphus lotus, for the first time to the best of our knowledge, according to a manufacturing process based on its chemical and thermal activation. These cores were chemically activated by sulfuric acid for 24 h and then carbonized at 500°C for 2 hours. The obtained activated carbon was characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and Brunauer–Emmett–Teller (BET) analysis. The adsorption of methylene blue (MB) on the activated carbon was evaluated, by Langmuir and Freundlich models examination, in order to explain the adsorption efficiency in a systematic and scientific way. Moreover, pseudo-first-order and pseudo-second-order kinetic models were used to identify the mechanisms of this adsorption process. The characterization results showed an important porosity (pore sizes ranging from 10 to 45 µm), a surface structure having acid groups and carboxylic functions, and a specific surface of 749.6 m²/g. Results of the MB adsorption showed that this process is very fast as more than 80% of MB is adsorbed during the first 20 minutes. In addition, increasing the contact time and temperature improves the MB removal process efficiency. Moreover, this adsorption's kinetic modeling follows the pseudo-second-order model. Furthermore, data on the adsorption isotherm showed a maximum adsorption capacity of 14.493 mg/g and fit better with the Langmuir model. The thermodynamic parameters (∆G₀, ∆S₀, and ∆H₀) indicate that the adsorption process is endothermic and spontaneous. Therefore, Ziziphus lotus can be used as a low-cost available material to prepare a high-quality activated carbon having a promising potential in the wastewater treatment.

The Role of Biomethane from Sewage Sludge in the Energy Transition: Potentials and Barriers in the Arab Gulf States Power Sector

The increasing energy and water demands by the Arab Gulf states highlight the importance of sustainable use of energy resources. Wastewater sludge management for energy recovery creates an opportunity for sector integration for both wastewater treatment plants and renewable energy production. The objective of this study was to theoretically estimate the biomethane potential of wastewater sludge, together with identification of the role of biomethane in the region. The prediction of biomethane potential was based on the theoretical stoichiometry of biomethanation reactions, using the R-based package ‘Process Biogas Data and Predict Biogas Production’. The biomethane potential of sludge ranges between 232–334 × 106 m3, with a total heat-value up to 10.7 trillion BTUs annually. The produced biomethane can generate up to 1665 GWh of electric energy, an equivalent amount to the current levels of electricity generation from wind and solar power combined. The findings from the case study on Kuwait’s indicate that biomethane could displace 13 × 106 m3 of natural gas, or approximately 86,000 barrels of crude oil, while simultaneously reducing greenhouse gas emissions by 86% when compared to the base-scenario. Despite its potential, biomethane recovery in the region is hindered by technical-, economic-, and policy-based barriers.

Assessing the Impact of Water Efficiency Policies on Qatar’s Electricity and Water Sectors

Water and electricity have a unique relationship in the modern world as one requires the other in a complex system of networks to supply the utility to the customers. This energy–water interaction is especially peculiar in the Gulf Cooperation Council, where there are limited water resources, but extremely high use rates. Qatar provides a unique case in terms of extreme water scarcity and excessive water use. To understand the intricate network, this paper establishes an updated and comprehensive qualitative model of the water system in the country with the help of a water balance and system dynamics (causal loop diagram) methodology. Regression estimates are then used to estimate future water and energy consumption in addition to carbon dioxide emissions until the year 2050. Finally, system dynamics (stock and flow diagram) is used to determine the supply impacts of efficiency policies including limiting of groundwater abstraction to only 50 million m3, reduction of water consumption in the household, commercial and industrial sector by 10%, and gradual increase in the share of reverse osmosis (RO)-produced desalinated water to 50% in order to assess the supply volume, electricity consumption and CO2 emissions. The efficient use of water in different sectors of the economy results in a combined saving of 1222 GWh (8.1%) or 594,000 tons CO2. Furthermore, by moving to membrane-based desalination technology energy consumption and carbon dioxide emissions can be reduced by 3672 GWh (24.3%) and 1.8 million tons CO2, respectively. Further results suggest that while replacing groundwater with desalinated water can increase the energy consumption significantly, reuse of treated wastewater has almost the same footprint as groundwater, but can increase the resilience of the system considerably as groundwater abstraction levels are lowered to their renewal rates.

Wastewater Refinery: Producing Multiple Valuable Outputs from Wastewater

A wastewater refinery is a multifunctional solution that combines different technologies and processing schemes to recover a spectrum of valuable materials from municipal or industrial wastewater. The concept of wastewater refinery introduces a new perspective on wastewater treatment and management. It aims at making the most of wastewater constituents by co-producing different worthful outputs, such as water, energy, nitrogen, sulfide, and phosphorous. This can turn the treatment of wastewater from a major cost into a source of profit. The wastewater refinery approach is well aligned with the concept of the circular economy. A case study on Qatar’s wastewater revealed the potential recovery of significant quantities of valuable resources embodied in the country’s wastewater. Valorization of organic constituents and the recovery of nitrogen, phosphorus, and sulfide should be given priority. To facilitate the adoption of the wastewater refinery concept, research is required to explore technical and economic bottlenecks.

Energy recovery and nutrients recycling from municipal sewage sludge

Hydrothermal Liquefaction (HTL) could be a promising and better alternative to other techniques for energy recovery from municipal sewage sludge (MSS). However, the nutrients (i.e., N, and P) recovery potential from the byproducts, generated in the HTL of MSS, needs to be studied so that a comprehensive sludge management practice could be adopted. In this study, HTL process temperature (275-400 °C), and reaction time (30-120 min) were first investigated for biocrude yield and release of the nutrients to the aqueous phase liquid (APL) and biochar. The maximum energy recovery (i.e., 59%) and maximum energy return on investment (i.e., 3.5) were obtained at 350 °C and 60 min of holding time. With the increase in HTL reaction time, the concentration of nitrogen in the APL increased (5.1 to 6.8 mg/L) while the concentration of phosphorus decreased (0.89 to 0.22 mg/L); the opposite was observed for the biochar. The nutrient recycling efficiency from the APL using microalgae was found to be strain-specific; nitrogen recycling efficiency by Picochlorum sp. and Chlorella sp. were 95.4 and 58.6%, respectively. The APL, derived from 1 kg MSS, could potentially produce 0.49 kg microalgal biomass. Since the concentrations of various metals in the biochar samples were substantially lower compared to their concentrations in raw MSS, the application of biochar as a soil conditioner could be very promising. Overall, net positive energy could be recovered from MSS using the HTL process, while the nutrients in the APL could be used to cultivate specific microalgae, and biochar could be applied to enhance the soil quality.

Agri-Food Markets in Qatar: Drivers, Trends, and Policy Responses

Agri-food markets are vital in achieving food security, especially for resource-poor, food-importing countries such as Qatar. The paper provides an overview of the evolution of agri-food markets in Qatar and explores the implications of past and ongoing changes in terms of food security and food system sustainability. In particular, the review analyzes drivers of changes, trends, and challenges as well as policy responses to address the emerging challenges while ensuring the country’s food security. It draws upon a systematic review of scholarly literature indexed in the Web of Science as well as data from gray literature (e.g., reports) and databases (e.g., FAOSTAT). Different drivers (e.g., population growth with huge expatriate inflow, urbanization, income increase) affected the functioning of agri-food markets as well as the structure of the food chain (viz. production, processing, distribution, consumption) in Qatar. In addition to drivers, the food-related trends were also shaped by numerous environmental (e.g., land/water scarcity), economic, health, and trade challenges. To ensure long-term food and nutrition security for its population, Qatar implemented various policies and strategies (e.g., National Food Security Strategy 2018–2023). In this context, agri-food markets, as functional links between production and consumption, can foster transition towards sustainable food consumption and production patterns in Qatar.

Decomposition Analysis of Factors Affecting Changes in Industrial Wastewater Emission Intensity in China: Based on a SSBM-GMI Approach

This paper investigated the factors driving the changes in industrial wastewater emission intensity (IWEI) across provinces in China. To do this, we proposed a Super-efficiency Slacks-based Measure-Global Malmquist Index (SSBM-GMI) to decompose the change in IWEI into the effects from efficiency change (ECE), technological change (TCE), capital–wastewater substitution (KWE) and labor–wastewater substitution (LWE). The method was applied to conduct an empirical study using Chinese provincial data from 2003–2015. The main findings include the following: firstly, TCE was the dominant driving force behind the reduction in IWEI with an average annual contribution of −6.4% at the national level, followed by KWE (−5.3%), LWE (−1.8%) and ECE (1.2%). Secondly, significant differences exist in the driving factors behind the reduction in IWEI across regions. The reduction in IWEIs in the Northeast area and the Great Northwest area was mainly driven by productivity growth, while the reduction in IWEIs in the other areas was mainly driven by factor substitution. Thirdly, the shortage of KWE and LWE has impeded IWEI reduction in the Great Northwest area, the Middle Reaches of the Yellow River, the Northeast area and the North area. Finally, some particular policy implications were also recommended for reducing industrial wastewater emission in China.