Selection of palm oil mill effluent treatment for biogas generation or compost production using an analytic hierarchy process

Palm oil mill effluent (POME) is the liquid waste from palm oil mills, and is generally treated using open lagoon technology. However, open lagoons can also be combined with more environmentally friendly technologies. In this study, the analytic hierarchy process (AHP) was used to determine the best combination open lagoon of technology (COLT) for POME treatment. The selected criteria were benefit, opportunity, risk, and cost, with sub-criteria further determined based on these criteria. The sub-criteria were revenue, greenhouse gas reduction, employment absorption, corporate social responsibility, co-processing, environmental risk, marketing risk, technology reliability, investment cost, operation and maintenance cost, and opportunity cost. The alternatives were COLT-composting for fertilizer purpose and COLT-biogas for energy generation purpose. Calculation and analysis was performed on questionnaire data using Expert Choice^®. COLT-composting proved to be the superior COLT using tentative performance of alternative in this research, with advantages in benefit, opportunity, and risk. The priority weight for COLT-composting was 0.636. Sensitivity analysis was performed by changing criteria priorities. For COLT-biogas to be considered better than COLT-composting, the cost would need to be weighted more than 0.954.     

Composting of municipal solid waste by different methods improved the growth of vegetables and reduced the health risks of cadmium and lead

Environmental Science and Pollution Research - Reutilization of putrescible municipal solid wastes (MSW) in agriculture can provide valuable plant nutrients. However, it may pose serious...     

Effect of Pb,Cd and Cu on survival and development of Culex quinquefasciatus (Diptera: Culicidae)

ABSTRACT

The present research aimed to determine the lowest levels of three heavy metals (Pb, Cd and Cu) to which the larvae of Southern House Mosquito, Culex quinquefasciatus are susceptible in water. The study also aimed to investigate the effects of these heavy metals on the development of Cx. quinquefasciatus at concentrations set by Pakistan Environmental Protection Agency (Pak-EPA) as permissible levels for liquid industrial effluents. The 2nd instar larvae of Cx. quinquefasciatus were exposed to different concentrations of Pb, Cd and Cu and their effects on oviposition preference, egg hatching rate and larval development were studied. The LC₅₀ values of Pb, Cd and Cu were 12.6, 6.3 and 2.6?ppm, respectively. Gravid female mosquito adults deposited a significantly lower number of egg rafts in containers containing 0.50?ppm Pb or 1.0?ppm Cu in water. Each of the heavy metals in water resulted in significantly (p?<?0.05) lower egg hatching rate, prolonged time to pupation, lower pupation rate, prolonged time to adult emergence, lower adult emergence rate and higher female to male ratio. It is concluded that the 2nd instar larvae of Cx. quinquefasciatus are susceptible to Pak-EPA permissible levels of Pb, Cd and Cu in municipal and liquid industrial effluents.     

Effect of bound residues of metsulfuron-methyl in soil on rice growth

A pot experiment was conducted to appraise the hazards of bound residues of metsulfuron-methyl in soil at six levels (0, 0.050, 0.089, 0.158, 0.281, and 0.500 mg kg(-1)) to the growth of four rice varieties (Xiushui 63, Eryou 810, Liangyoupeijiu, and Zhenong 952). The morphological characteristics of rice roots like root number, total length, surface area of rice roots, and rice biomass were determined. The results showed that the bound residues of metsulfuron-methyl in soil impacted the growth of rice. Root number, total length of roots, surface area of roots, and biomass were restrained by bound residues of metsulfuron-methyl in soil. The inhibition rate of root growth increased from 69.46-81.32% to 85.18-95.97% with the increasing of levels of bound residues of metsulfuron-methyl from 0.05 mg kg(-1) to 0.50 mg kg(-1). The number of rice roots could be taken as a sensitive index to screen the rice varieties endurable to bound residues of metsulfuron-methyl in soil and to predict the potential hazards of bound residues of metsulfuron-methyl in soil to rice. The level of bound residues of metsulfuron-methyl in soil causing the root numbers decreased by 50% (IC50) followed the order of Xiushui 63 < Eryou 810 < Liangyoupeijiu < Zhenong 952.     

Adsorption kinetics and modeling of H2S by treated waste oil fly ash

Waste oil fly ash (OFA) collected from disposal of power generation plants was treated by physicochemical activation technique to improve the surface properties of OFA. This synthesized material was further used for potential hydrogen sulfide (H₂S) adsorption from synthetic natural gas. The raw OFA was basically modified with a mixture of acids (20% nitric acid [HNO₃] and 80% phosphoric acid [H₃PO₄]), and it was further treated with 2 M potassium hydroxide (KOH) to enhance the surface affinity as well as surface area of synthesized activated carbon. Correspondingly, it enhanced the adsorption of H₂S. Crystallinity, surface morphology, and pore volume distribution of prepared activated carbon were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) analyses. Fourier transform infrared (FTIR) study was also performed to identify the functional groups during different synthesis stages of modified activated carbon. The Langmuir, Freundlich, Sips, and dual-site Langmuir (DSL) models were used to study the kinetic and breakthrough behavior of H₂S adsorption over alkali-modified activated carbon. Modeling results of isotherms indicated that OFA has dual sites with high and low affinity for H₂S adsorption. The Clark model, Thomas model, and Yoon-Nelson model were used to examine the effects of flow rate and inlet concentration on the adsorption of H₂S. Maximum uptake capacity of 8.5 mg/g was achieved at 100 ppm inlet concentration and flow rate of 0.2 L/min.

Implications: Utilization of worthless oil fly ash from power plant is important not only for cleaning the environment but also for solid waste minimization. This research scope is to eradicate one pollutant by using another pollutant (waste ash) as a raw material. Chemical functionalization of synthesized activated carbon from oil fly ash would lead to attachment of functional groups of basic nature to attract the acidic H₂S. Such type of treatment can enhance the uptake capacity of sorbent several times.