Utilization and life cycle assessment of low activity solid waste as cementitious materials: A case study of titanium slag and granulated blast furnace slag

The dumping of cement production and industrial solid waste can cause severe environmental impact. In order to reduce the environmental impact of cement production and reasonably dispose of solid waste, a new type of cementing material was developed using industrial solid waste as raw materials. It solves the problem that low activity solid waste is difficult to reuse and makes up for the less research, which considered both preparation and environmental evaluation. The orthogonal tests of cement mortar strength as well as life cycle assessment were carried out. The results from variance and range analyses of the orthogonal tests revealed that the fraction of solid waste mainly affected the compressive strength of the solid waste cement mortar, and its specific surface area primarily influenced the flexural strength. After curing for 28 days, the compressive and flexural strength values of the developed cementing material were 40.6 MPa and 8.6 MPa, respectively. The results of life cycle impact assessment indicated that the developed solid waste cement had more environmental advantages than ordinary cement in 18 midpoints environmental impact types, and could diminish environmental impact by 16.1 % on the whole. The solid waste cement has achieved great environmental gains in the human toxicity, natural land transformation, metal depletion, climate change and other environmental impact categories. In addition, the clinker calcination, transportation and material mining were identified as critical processes responsible for the human toxicity, natural land transformation and metal depletion. Through sensitivity and uncertainty analyses, the development of the solid waste cement was proved to be the most effective method to decrease the environmental impact of cement. Finally, the methods of further reducing the environmental impact of cement were proposed.

The noteworthy chloride ions in reclaimed water: Harmful effects, concentration levels and control strategies

Chloride ions (Cl^-), which are omnipresent in reclaimed water, can cause various problems in water reuse systems, especially during water transmission and at end use sites. Although reverse osmosis (RO) is considered as an effective technology to reduce chloride, its high investment and complex maintenance requirements hinder its application in many water reclamation plants (WRPs). Recently, several technologies bringing new options to better deal with chloride have gained increased attention. This review provides detailed information on the harmful effects, concentration levels, and sources of chloride in reclaimed water and summarizes and discusses various chloride removal technologies, including non-selective methods (e.g., membrane filtration, adsorption and ion exchange, oxidation, and electrochemical methods) and selective methods (e.g. precipitation and specially designed electrochemical methods). Among these, Friedel's salt precipitation and capacitive deionization showed attractive development potential. This review also proposes a holistic framework for chloride control from aspects of "Fit-for-Purpose" planning, technical system development, and whole process optimization, which could facilitate the planning and operation of long-term sustainable water reuse practices.

Life cycle assessment of underground coal mining in China

Coal is not only the main fossil fuel in China but also a pollution source. To evaluate the impact of coal production on the environment, a life cycle assessment (LCA) was conducted on the mining process of a typical coal mine in China by using the SimaPro 9.0.0 software. The Ecoinvent v3 database was used to provide the background data, and midpoint results with uncertainty information were calculated using the ReCiPe Midpoint (H) method. After normalising the midpoint results, fossil depletion was identified as the most predominant environmental impact category, followed by marine ecotoxicity, freshwater ecotoxicity, climate change, freshwater eutrophication, and human toxicity. The contribution analysis indicates that coal mining activities, consumption of steel and electricity, and mine ventilation are the key processes causing the above-mentioned environmental impact categories, which should be paid special attention. According to the sensitivity analysis, the primary countermeasures for addressing the environmental issues are to reduce the mining activities and improve the efficiency of coal mining and utilisation. In addition, the quantitative and comparative analyses show that the gas extraction production mode is beneficial to the environment. Finally, technical measures were proposed to promote green and sustainable development of the coal industry. This research can provide guidance for ensuring national energy security and promoting healthy development of the national economy.

Inhalation and dermal exposure of workers during timber impregnation with creosote and subsequent processing of impregnated wood

OBJECTIVES

Coal tar creosote oils are used as highly effective wood protectants for, e.g., railway sleepers, utility poles and marine pilings. For impregnation of wood, the hot creosote oil is mostly applied in vacuum processes and by hot-and-cold dipping. From the perspective of an occupational hygienist, creosote tar oils are problematic because they have a number of hazardous properties, including carcinogenicity. We have studied inhalation and dermal exposure in six and four impregnation plants, respectively, in Germany. Some plants were visited repeatedly, for up to five measurement campaigns conducted over several years. Inhalation and dermal exposure resulting from vacuum impregnation and from hot-and-cold dipping, as well as secondary exposure resulting from assembly of impregnated railway sleepers have been measured. Accompanying, human biomonitoring of the employees has been performed.

METHODS

Inhalation exposure was measured using personal air samplers, collecting particles and vapours simultaneously. Dermal exposure was investigated by whole body dosimetry using disposable chemical protective coveralls and split leather gloves. 18 polycyclic aromatic hydrocarbons (PAHs) have been determined separately by high performance liquid chromatography (HPLC) or gas chromatography-mass spectrometry (GC-MS), respectively. For human biomonitoring 1-hydroxypyrene (1-OHP) in urine related to creatinine has been measured using HPLC. Both, pre- and post-shift values have been determined for this metabolite.

RESULTS

Dermal exposure towards pyrene and the sum of the determined 18 PAHs as well as inhalation exposure to naphthalene, pyrene and the sum of the determined 18 PAHs are presented in this paper. The plants performing vacuum impregnation have employed different constructive, technical and organisational measures, and some measures have also changed between the different measurement campaigns. We have found that cooling the vacuum impregnation vessel before unloading can reduce inhalation exposure to about one-third. However, our data shows that installation of structural or technical risk management measures (RMM) did not always reduce the exposure as intended, and can even lead to increased exposure in adverse constellations. Dermal exposure was strongly affected by differences in the working procedures. Measurements performed during assembly of impregnated railway sleepers indicate that secondary exposure leads to lower inhalation, but similar dermal exposure compared to the impregnation processes. Also 1-OHP excretion rates are similar after impregnation process and after assembly of impregnated railway sleepers.

CONCLUSION

Our recent data underlines that efficient reduction of the exposure resulting from impregnation with creosote requires sophisticated risk reduction strategies. Structural measures such as the enclosure of the loading area and technical measures like local exhaust ventilation shall be coordinated carefully with organisational measures and provision of personal protective equipment. The data presented here represents a broad bandwidth of current workplace situations in the creosote oil processing industry and is therefore suitable for risk assessment in related plants as well as under regulatory frameworks like the European Biocides Regulation. Each plant in this investigation was unique. Together they represent the whole width of this branch in Germany. Additionally, the number of plants and exposed workers is limited and relative low. Therefore, a comprehensive consideration and statistical analysis were not feasible.