Heavy metal exposure from co-processing of hazardous wastes for cement production and associated human risk assessment

This study was carried out to determine the concentration of heavy metals (Cd, Ni, Pb, Cr, Ni and Zn) in ordinary Portland cement (OPC) produced from the co-processing with hazardous waste in comparison with OPC produced using natural raw materials. The results showed that the concentration of heavy metals in cement produced from natural raw material was in the order of Zn > Pb > Cr > Ni > Cu > Cd. Zn and Cd were the highest and the lowest concentrations, respectively, in cements produced from the co-processing activity. The difference between heavy metals concentrations in OPC produced with and without co-processing was found to be statistically significant. The concentration of heavy metals in the cement produced is generally factory dependent. The human risk assessment associated with the heavy metals for non-carcinogenic and carcinogenic risks has been evaluated. The calculated hazard index (HI) and total lifetime cancer risks (LCR) were lower than the acceptable threshold reference values, HI < 1 and LCR < 1 × 10^?4, respectively. Thus, it is anticipated that there is no potential of non-carcinogenic and carcinogenic risks for both adult and children. However, the findings indicated that there is a need for regulatory monitoring. The exposure pathway for both non-carcinogenic and carcinogenic risks are both in the order of ingestion > dermal > inhalation.     

Management of shock loads wastewater produced from water heaters industry

Water heater manufacturing represents one sector of household electrical appliance industry. It includes several batch processes which resulted in a highly polluted wastewater as shock loads. The objective of this study was to manage the shock loads wastewater with a simple and cost-effective approach prior to final discharge into municipality. To achieve this objective, two approaches were studied. The first approach was the chemical treatment of the accumulated shock loads wastewater using alum and an anionic polymer. Although this approach produced a very high-quality effluent, it was economically and technically infeasible. The second approach was a controlled release of the shock loads to the normal daily discharge in a way that guarantees the compliance of the end-off-pipe with the National Regulatory Standards. This solution required establishment of an equalization tank for normal daily flow and a holding tank for controlled release of the shock loads. Mathematical calculations were carried out to determine the most violating parameters in order to calculate the mixing ratio the of shock loads with the normal daily flow. Full engineering design of the proposed solution was carried out. This approach was implemented and proved to be simple, easy to operate, cost-effective and can be replicated in similar batch processing manufacturing plants.     

Improving the indoor air quality using the individual air supply system

Indoor air quality attracts great interest. Many dwellings are ventilated naturally. The article presents the gravity system conversion into individual air supply system, which can be equipped with air fan. This solution’s impact on the interior microclimate was analyzed. The proposed solution uses the lower natural ventilation ducts sections, which are not normally used as air supply channels to bring air to the housing. Exhaust grilles were located in the adjacent rooms. Individual air supply system with switched off fan improves indoor air quality insufficiently; however, switching on the device causes a very significant change. A large carbon dioxide concentration reduction (which was used as an air quality indicator) has been confirmed by rigorous statistical analysis, the results of which were presented in the article.     

Water stress index and its implication for agricultural land-use policy in Thailand

Land-use change and expansion for agriculture significantly affect freshwater resource availability which in turn results in different levels of water scarcity and competition among users in different areas and time. The study uses the water stress index as an indicator for determining the potential impact of water use considering water deprivation potential. Considering the case of Thailand, the temporal aspects of water withdrawal and availability have been analyzed and characterized as the monthly water stress index for the 25 watersheds in the country. Wide variations of monthly water stress index are obtained; extreme water stress is observed in the areas of the Chao Phraya and Tha Chin watersheds (the central region) during the dry season because of the large areas cultivating second rice (rice planted in dry season). The target of the Thai government on agricultural land-use change and zoning toward the conversion of about 0.37 M·ha of the upland paddy fields with low productivity to sugarcane was evaluated showing serious implications on the monthly water stress index of the relevant watersheds and the water scarcity footprint potentials of rice and sugarcane production. The results reveal that proper policy can help reduce the amount of water requirement for agriculture in June, July, August and September by about 60–220 M·m³, which in turn results in the decrease in monthly water stress index values. Nevertheless, appropriate measures of water resource management for agriculture still need to be designed to avoid water competition as well as protect the ecosystem.     

Removal of diazinon pesticide from aqueous solutions using MCM-41 type materials: isotherms,kinetics and thermodynamics

In this research, ordered mesoporous silica, including MCM-41, was synthesized via sol–gel process and a propyl methacrylate-modified ordered mesoporous silica (MPS-MCM-41) was successfully synthesized via a postsynthesis grafting process. Then both MCM-41 and MPS-MCM-41 were characterized using FTIR, XRD, SEM and BET techniques. The synthesized materials were utilized as adsorbent for removal of diazinon pesticide from aqueous solutions. The effects of pH, contact time, adsorbent dose, initial concentration and temperature have been evaluated using removal efficiencies. Also, the kinetic, thermodynamic and isotherm models of diazinon adsorption were studied for the both MCM-41 and MPS-MCM-41. The results showed that the maximum adsorption capacities are 142 and 254 mg g^?1 for the MCM-41 and MPS-MCM-41, respectively, at the initial concentration of 50 mg L^?1, temperature of 298 K and adsorbent dose of 0.1 g L^?1. The highest percentages of diazinon removal are 56.4 and 87.2 (at adsorbent dose of 2 g L^?1 and the temperature of 318 K) for the MCM-41 and MPS-MCM-41, respectively. The Freundlich and Langmuir models are more compatible for describing equilibrium data of the diazinon adsorption capacity on the MCM-41 and MPS-MCM-41, respectively. Thermodynamic study indicated that the adsorption process of diazinon onto MCM-41 and MPS-MCM-41 is exothermic and has a spontaneous nature. The higher adsorption capacity and higher spontaneous nature of MPS-MCM-41 in comparison with MCM-41 might be due to the presence of the both hydrogen bonding and hydrophobic interaction between surface functional groups of MPS-MCM-41 (hydroxyl and propyl methacrylate) and diazinon functional groups.     

Determining ammonia nitrogen decay rate of Malaysian river water in a laboratory flume

There is lack of information regarding ammonia nitrogen (AN), (i.e. NH₃-N) decay rate of river water in tropical regions like Malaysia. AN decay rate is a very important kinetic parameter to estimate NH₃-N, nitrate nitrogen (NO₃-N) and dissolved oxygen concentrations of river water by using computer models. This study presents determination of ammonia nitrogen decay rate of river water in the tropical environment of Malaysia. A laboratory flume was used to conduct twelve experiments. The flume was used to represent the turbulent condition of a typical river. Ammonia nitrogen decay rate for the tropical environment of Malaysia was observed to be between 0.194 and 0.554 per day. Median value of AN decay rate was 0.26 per day, which is slightly lower than the global median value of 0.295 per day. To check the accuracy of flume experiments, the AN decay rate of Pusu River obtained from the flume experiment was used to calibrate and validate ammonia nitrogen concentration of the river by using water quality analysis and simulation program (WASP). Very good calibration and validation results were achieved, which substantiated the accuracy of the flume experiments.     

Short-term greenhouse emission lowering effect of biochars from solid organic municipal wastes

Qatar economy has been growing rapidly during the last two decades during which waste generation and greenhouse gas emissions increased exponentially making them among the main environmental challenges facing the country. Production of biochar from municipal solid organic wastes (SOWs) for soil application may offer a sustainable waste management strategy while improving crop productivity and sequestering carbon. This study was conducted to (1) investigate the physicochemical parameters of biochars for SOW, (2) select the best-performing biochars for soil fertility, and (3) evaluate the potential benefits of these biochars in lowering greenhouse gases (GHGs) during soil incubation. Biochars were produced from SOW at pyrolysis temperatures of 300–750 °C and residence times of 2–6 h. Biochars were characterized before use in soil incubation to select the best-performing treatment and evaluation of potential GHG-lowering effect using CO₂ emission as proxy. Here, soil–biochar mixtures (0–2%w/w) were incubated in greenhouse settings for 120 days at 10% soil moisture. Soil properties, such as pH, EC, TC, and WHC, were significantly improved after soil amendment with biochar. Two biochars produced from mixed materials at 300–500 °C for 2 h and used at 0.5–1% application rate performed the best in enhancing soil fertility parameters. A significant decrease in CO₂ emission was observed in vials with soil–biochar mixtures, especially for biochars produced at 500 °C compared the corresponding raw materials which exhibited an exponential increase in the CO₂ emission. Hence, application of biochar to agricultural soils could be beneficial for simultaneously improving soil fertility/crop productivity while sequestering carbon, thereby reducing anthropogenic emissions of GHGs.     

Photodegradation of dimethyl phthalate (DMP) by UV–TiO<Subscript>2</Subscript> in aqueous solution: operational parameters and kinetic analysis

In this paper, the adsorption and degradation phenomenon involved in the photocatalytic degradation of dimethyl phthalates (DMPs) by titanium dioxide (TiO₂) was studied. A variety of operating variables were selected firstly. Then, it was proved that even for such weak adsorption properties molecules as DMP, adsorption was still an important prerequisite for photolysis. A surface-mediated reaction process was proposed that the photodegradation of DMP assisted by TiO₂ particles occurred primarily at the surface of the photocatalyst rather than in the homogeneous phase. According to Langmuir–Hinshelwood model, the adsorption constant determined from the dark adsorption was far less than that obtained in the light condition. Enhanced DMP adsorption on the surface of TiO₂ under irradiation was the possible reason for the improvement of photodegradation efficiency. Under the irradiation of light, a synergistic mechanism of adsorption and photocatalysis was responsible for DMP degradation. The quantitative analysis by adding scavengers indicated that ^·OH radical was primarily responsible for the photodegradation of DMP. It was further verified that ^·OH was produced much more from conduction band electrons rather than valance band holes toward photodegradation of DMP by adding foreign Cu²⁺.     

Effect of confining stress and loading frequency on dynamic behavior of municipal solid waste in Kahrizak landfill

In order to analyze the stability of a landfill site, it should analyze some properties of waste introducing the main structural elements. Up to now, it has not been done much research on the properties of municipal solid waste. In addition, due to the differences in waste properties from one country to another and even from one to another landfill site, it is impossible to generalize the results. These conditions caused local research on the evaluation of static and dynamic parameters of municipal solid waste to be done. Because Iran is a seismic country, the short-term behavior of waste controls landfill sites stability during seismic loads; so it is necessary to know the dynamic behavior of these materials. In this paper, about 18 cyclic tests were performed, and in addition to determining the dynamic parameters of municipal solid waste of Tehran Kahrizak Disposal Site using cyclic triaxial test, the effect of confining stress and loading frequency on dynamic properties of these materials was evaluated. The results have shown that with increasing the confining stress and loading frequency, shear modulus and damping ratio was increased and decreased, respectively, and it is related to the composition of the municipal solid waste materials.     

Preservation of thermophilic mixed culture for anaerobic palm oil mill effluent treatment by convective drying methods

The generation of huge amount of liquid waste known as palm oil mill effluent is a major problem in oil palm industry. Meanwhile, anaerobic biodegradation of such organic effluent at thermophilic condition is a promising treatment technology due to its high efficiency. However, storage and transportation of thermophilic mixed culture sludge are challenging due to constant biogas generation and heating requirement. Hence, drying of thermophilic sludge was conducted to obtain dormant thermophiles and thus enables easier handling. In this study, thermophilic sludge was dried using heat pump at 22 and 32 °C as well as hot air oven at 40, 50, 60, and 70 °C. Subsequently, quality of dried sludge was examined based on most probable number enumeration, chemical oxygen demand, and methane yield. Average drying rate was found to increase from 3.21 to 17.84 g H₂O/m² min as drying temperatures increases while average moisture diffusivity values ranges from 5.07 × 10^?9 to 4.34 × 10^?8 m²/s. Oven drying of thermophilic mixed culture resulted in highest chemical oxygen demand removal and lowest log reduction of anaerobes at 53.41% and 2.16, respectively, while heat pump drying resulted in the highest methane yield and lowest log reduction of methanogens at 53.4 ml CH₄/g COD and 2.09, respectively. To conclude, heat pump at 22 °C was most suitable drying technique for thermophilic mixed culture as the original methane-producing capability was largely retained after drying, at a slightly lower yet still comparable chemical oxygen demand removal when palm oil mill effluent was treated with the rehydrated culture.