Issues related to the wearing of fall-arrest harnesses in the construction industry

Work-related falls continues to be one of the leading causes of fatalities in the Australian construction industry, and the failure to use fall protection equipment, such as fall-arrest harnesses and arresting devices, has been found to be a contributing factor. In an attempt to gain an understanding of the issues surrounding the use of fallarrest harness systems by construction workers a study involving semi-structured interviews of 15 male construction workers was carried out at three construction sites. The majority of interviewees commented that there was discomfort in wearing a fall-arrest harness; that there were a number of problems when anchored via an arresting device; and that using a fall-arrest system reduced productivity. Most of the interviewees considered that they needed safety precautions against falls, and they expressed the view that workers’ attitudes towards safety depended critically upon their supervisors’ attitude towards safety. It was also found that workers were not trained in rescue procedures. Interviewees expressed concern that retrieval of a suspended worker may not be carried out in time to prevent the onset of suspension trauma. A number of issues were identified which require further research, such as, investigation into suspension trauma, harness and arresting device design, training provided to workers, and the provision for rescues.

Online titrimetric and off-gas analysis for examining nitrification processes in wastewater treatment

The two steps of nitrification, namely the oxidation of ammonia to nitrite and nitrite to nitrate, often need to be considered separately in process studies. For a detailed examination, it is desirable to monitor the two-step sequence using online measurements. In this paper, the use of online titrimetric and off-gas analysis (TOGA) methods for the examination of the process is presented. Using the known reaction stoichiometry, combination of the measured signals (rates of hydrogen ion production, oxygen uptake and carbon dioxide transfer) allows the determination of the three key process rates, namely the ammonia consumption rate, the nitrite accumulation rate and the nitrate production rate. Individual reaction rates determined with the TOGA sensor under a number of operation conditions are presented. The rates calculated directly from the measured signals are compared with those obtained from offline liquid sample analysis. Statistical analysis confirms that the results from the two approaches match well. This result could not have been guaranteed using alternative online methods. As a case study, the influences of pH and dissolved oxygen (DO) on nitrite accumulation are tested using the proposed method. It is shown that nitrite accumulation decreased with increasing DO and pH. Possible reasons for these observations are discussed. (C) 2003 Elsevier Science Ltd. All rights reserved.