Simulation of dense non-aqueous phase liquid remediation through steam-enhanced extraction

Steam-enhanced extraction has been reviewed by many researchers as an innovative technology to remediate dense non-aqueous phase liquid (DNAPL) from subsurface. However, the application of steam-enhanced extraction to heterogeneous subsurface conditions is still obscurity and its implementation is limited due to steam flow sensitivity to site characterization. Two-dimensional (2-D) simulations were performed to assess the efficiency of steam-enhanced extraction in remediation of heterogeneous subsurface contaminated with tetrachloroethylene (PCE) spill. The simulation was performed with four different steam injection rates. The results shows that increased in steam injection rate will increase the PCE remediation time. The steam injection with the rate of 1.0 x 10-4 kg/s was successfully removing 100% of the PCE. There are significant impacts in the difference in remediation time with the increment approximately 20 min, 40 min and 70 min for every 2.0 x 10-5 kg/s increment. The dominant mechanisms of PCE removal is physical displacement through vaporization and co-boiling enhanced by steam distillation and steam stripping. The simulation results of steam-enhanced extraction for PCE removal was compared with surfactant-enhanced method implemented in existing experimental study. It was discovered that the time required to remove PCE using steam-enhanced extraction is four times faster than the time required to remove PCE using surfactant-enhanced method. This shows the capability of steam-enhanced extraction to recover contaminant more effectively. Steam-enhanced extraction has a greatest potential to decrease clean-up time which will offset greater capitol cost of the system

Antibiotics in the environment: mini review

Knowledge of pharmaceuticals in the environment is merely minute. Pharmaceuticals can enter the aquatic environment through the sewage treatment systems when they are excreted by people, or if they are disposed in the home. They can also enter sewage treatment works or waterways as a result of discharges from pharmaceutical manufacturing plants or medical establishments. The emission routes of veterinary drugs and feed additives to surface water are more complex than those of human pharmaceuticals. Emission to the surface water can take place either directly, when the animals are kept on pasture or indirectly by run-off and leaching through the soil. From an environmental side, the major effect of antibiotics is the toxic effect that may be exerted on aquatic organisms and disruption of the ecological balance. In addition, the presence of antibiotics in natural systems leads to the development of multi-resistant strains of bacteria. This paper outlines the different anticipated exposure routes to the environment, present knowledge of occurrence, fate and effect of pharmaceuticals

Performance of an innovative multi-stage anaerobic reactor during start-up period

Start-up of an anaerobic reactor is a relatively delicate process and depends on various factors such as wastewater composition, available inoculum, operating conditions and reactor configuration. Accordingly, systematized operational procedures are important, mainly during the start-up of an anaerobic reactor. In this paper, the start-up performance of an innovative multi-stage anaerobic reactor using synthetic wastewater at various organic loading rates (OLRs) was investigated. In Phase 1 of the experimental study, the reactor was operated at hydraulic retention time (HRT) of 1 day with corresponding OLR of 1.07 kg COD.m-3.d-1. Thereafter, the reactor was operated at intermittent feeding (Phase 2), with HRT of 1.4 day and OLR of 0.82 to 2.45 kg COD.m-3.d-1. Results showed up to 71% COD reduction in the Phase 1 of the experimental study. However, in Phase 2, when the reactor was operated at intermittent feeding, the COD removal efficiency increased from 75 to 92%. It can be concluded that the multi-stage anaerobic reactor system performed better at intermittent feeding, indicating that the reactor required low loading rate and sufficient HRT for gradual acclimatization for reactor start-up. The reduction of the period necessary for the start-up and improved operational control are important factors to increase the efficiency the reactor system.Key words: Anaerobic reactor start-up, biomass, glucose wastewater, intermittent feeding, multi-stage anaerobic reactor

Treatment of Textile Wastewater Using a Novel Electrocoagulation Reactor Design

This study explored the best operating conditions for a novel electrocoagulation (EC) reactor with the rotating anode for textile wastewater treatment. The influence of operating parameters like interelectrode distance (IED), current density (CD), temperature, pH, operating time (RT) and rotation speed on the removal efficiency of the contaminant was studied. A comparative study was done using conventional model with static electrodes in two phases under same textile wastewater. The findings revealed that the optimal conditions for textile wastewater treatment were attained at RT = 10 min, CD = 4 mA/cm2, rotation speed = 150 rpm, temperature = 25°C, IED = 1 cm and pH = 4.57. The removal efficiencies of color, biological oxygen demand (BOD), turbidity, chemical oxygen demand (COD) and total suspended solid (TSS) were 98.50, 95.55, 96, 98 and 97.10%, respectively, within the first 10 min of the reaction. The results of the experiment reveal that the newly designed reactor incorporated with cathode rings and rotated anode impellers provide a superior treatment efficiency within a short reaction time. The novel EC reactor with a rotating anode significantly enhanced textile wastewater treatment compared to the conventional model. The values of adsorption and passivation resistance validated the pollutants removal rate

Bioenergy production and nutrients removal by green microalgae with cultivation from agro-wastewater palm oil mill effluent (POME) - A review

Environmental pollution specifically wastewater is gaining attention both in the developed and developing countries. Malaysia is considered as one of the major palm oil producers in the world. Therefore, it is important to develop an environmental friendly and economic method to treat palm oil mill effluent (POME). The wastewater can serve as an economical nutrient source or substrate that can support the cultivation of microalgae. This can be a great nutrient for algal cultivation at the same time as remediating effluent and generating biomass. Nowadays, many microalgae species are being investigated to determine their potential and effectiveness for phytoremediation application, especially high growth rate. However, using synthetic media for growing microalgae in a mass scale is costly. It is acknowledged that POME (as nutrients enriched media) assisted enhanced microalgae growth under certain condition can considerably reduce the presence of organic and inorganic compounds. In this review, the potential of wide range of the predominant microalgae species with main focus on green microalgae (high removal efficiency): Chlamydomonas sp and Chlorella sp were investigated. Moreover, we discussed about the history, methods and future prospects in nutrients removal by green microalgae comprehensively. This review discusses several potential strategies for tackling the environmental issue generated by agro-waste water POME with enhancement of biomass productivity which can be used as an alternative for energy production

Integrated approach as sustainable environment technique for managing construction waste : a review

The construction industry was reported as a major consumer of natural resources worldwide. Almost 60% of the natural resources consumed by this industry have caused a lot of environmental impacts on humans and the environment. Among the impacts were the disruption of human water sources, changes in the biological ecosystem and disruption of the food supply chain among biological factors. Countries around the world have enforced several laws and regulations. Apart from that, waste management technologies were formulated by government agencies and the world’s researchers were among initiatives to minimise the waste generation rate. Several technologies, such as recycling and recovery technologies were highlighted to be very efficient in minimising the waste accumulation rate. This paper discussed an integrated concept for managing construction waste in a sustainable manner. The integrated approach has adopted the reuse method, central sorting facilities, recycling facilities, thermal treatment facilities and disposal facilities. Implementations of these integrated approaches were able to save the world’s raw materials and natural energy sources as well as reducing the impacts of pollution on the environment

Performance of an up-flow anaerobic sludge bed (UASB) reactor treating landfill leachate containing heavy metals and formaldehyde

Municipal Solid Waste (MSW) landfill leachate is a serious environmental issue and treated using various methods, mostly involving biological treatment. In the present study, an up-flow anaerobic sludge bed (UASB) was used for the treatment of matured landfill leachate that contains heavy metals (As, Fe, Ni, and Cd) and Formaldehyde (FA). Accordingly, the OLR to the UASB reactor was gradually increased from 0.125 to 2.5 kg CODm-3d-1, to observe the process performance. The process performance of the reactor was characterized in terms of pH, Chemical Oxygen Demand (COD) removal, Total Volatile Acid (TVA) production, Mixed Liquor Suspended Solids (MLSS), Mixed Liquor Volatile Suspended Solids (MLVSS) washout, and Methane composition. Results showed that at a Hydraulic Retention Time (HRT) of 4 days and an OLR of 0.125 kg CODm-3d-1, up to 79.04% COD removal efficiency was observed. However, when the OLR was increased gradually from 0.375 to 2.5 kg CODm-3d-1, the COD removal efficiency decreased to 9.5%, suggesting that the high accumulation of heavy metals may have inhibited the methanogens. During this period, the heavy metal and formaldehyde concentration were 9.40, 0.43, 0.50, 12.80 and 8.60 mgL-1 respectively

Surfactant-alcohol experiments for dense non-aqueous phase liquid removal: a review

The aim of this paper is to review and to summarize the existing laboratory experiment studies from other researchers regarding surfactant alcohol experiment for dense non-aqueous phase liquid (DNAPL) removal, their approach, method of measurement, factor consideration and their findings together with result discussion. This review includes the selection of surfactant-alcohol, their important characteristics in the remediation of DNAPL, the laboratory experimental setup using 2-D laboratory model and enhanced remediation of DNAPL from recent laboratory studies. It has been shown in the laboratory experiment studies that solubilization is the dominant removal process of DNAPL. After surfactant concentration reached the critical micelle concentration, interfacial tension between DNAPL, water and soil decreased. This has resulted in increasing of solubility and removal rate of DNAPL. Mobilization also takes place in the removal process. However, most of the laboratory experiments did not consider other factor such as soil permeability, soil texture, and interfacial tension between soil and DNAPL. Further studies of surfactant-alcohol flushing shall be considered in the near future

Palm Oil Mill Effluent as an Environmental Pollutant

In recent decades, Malaysia has been known as one of the world’s leading producers and exporters of palm oil products. Every year, the number of palm oil mills increases rapidly, thus increasing the capacity of fresh fruit bunch waste or effluent discharge. Based on the data from the Malaysian Palm Oil Board in 2012, Malaysia produced 99.85 million tons of fresh fruit bunch (FFB) per year. However, about 5–5.7 tons of water was required in order to sterilize the palm fruit bunches and clarify the extracted oil to produce 1 ton of crude palm oil resulting in 50% of the water turning into palm oil mill effluent (POME). POME is one of the major environmental pollutants in Malaysia. The characteristics of POME and its behavior, if discharged directly, in water are described in this chapter. The suspended solid and nutrient content in POME could be able to support the growth of algae. This chapter aims to demonstrate that POME could be used as a main source for algae production, and this effluent is one of the main environmental problems in the tropical region especially in Malaysia

Treatment of wastewater using response surface methodology: a brief review

Response surface methodology (RSM) is widely applied to gathering knowledge on the interactions among parameters that require optimization during the treatment of wastewater. It can be used to optimize parameters during the process of treating wastewater, e.g., landfill leachate. The experimental design methods are useful to evaluate the parameters involved in a treatment with the minimum number of experiments. This will reduce the need for reagents and materials for experiments, which finally causes both time and expense to be increased. Anaerobic digestion of wastewater technologies escalated depending on the design configuration of the reactor. Several important parameters are taken into consideration in designing an anaerobic reactor such as operating conditions, seed sludge, wastewater composition and mixing. To construct a highly efficient degradation system, it is necessary to optimize such effective parameters. As a result, the advanced statistical design is used for process characterization, optimization and modelling. In this paper, the fundamentals of RSM and its application in the anaerobic treatment of wastewater was discussed in brief. The various works done in an anaerobic reactor using RSM for prediction and optimization are given