الفهرس 
Introduction and Aim of the StudyOnly 14 pages are availabe for public view
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Abstract
Amalgam has been used by dentists for more than 150 years for dental restorations traditionally called “silver fillings”. Dental amalgam used in Egypt typically contains up to about 50% mercury, silver (20-30%), tin (10%), copper (1-15%) and other metals (0-5%).
Mercury which is used in the form of dental amalgam, can reach the environment when amalgam waste is disposed into the sewerage. However, wastewater which is partially treated still illegally discharged into agriculture drains, lakes, sea water and Nile River.
A significant source of mercury pollution in water is dental amalgam as it often considered to be the largest source of mercury in municipal wastewater. Mercury as an alloy in amalgam has very high specific gravity, therefore almost all amalgam particles are expected to settle out at treatment plants within sludge.
This study is aimed at determination of mercury level, solids profile and flow rate of the wastewater in the dental unit at Alexandria Medical Research Institute by the conventional basic filter. It also measured the mercury level after applying the proposed filters made of woven and non-woven fabric filters to test the efficacy of both in retaining the solids containing mercury. This performance will develop a new technique on mercury removal.
To carry out the study, 180 anatomical replica teeth were divided into three groups (I, II and III), 60 teeth each. The teeth had been prepared and restored with three different weights of dental amalgam 400 mg, 600 mg and 800 mg for groups I, II and III, respectively.
The detection of the mercury level, solids profile and flow rate were determined according to the Standard Methods for the Examination of Water and Wastewater.
The present study revealed the following results:
• The mean of removal percentage of total solids using the proposed non-woven filters ranged from 51.7% by using filter A to 78% by application of filter C. Woven filter D can remove about 71% of total solids.
• It is obvious from the study that filter C (non-woven fabric filter) had the highest removal percentage reaching 98.7% of suspended solids.The mean of removal percentage of suspended solids using the other non-woven filters (A and B) were 69.6% and 80.1%, respectively. Woven filter D was highly removal upto 98% of suspended solids.
• Regarding the removal percentage of settleable solids after 10 and 30 minutesdetention time was about 97% using fabric filter C while filter D recorded the least removal percentage in the proposed filters to show about 65%. It was recognized that there was high removal percentage reaching 94% in filter A and B.
• Study revealed that the mean of removal percentage of mercury concentration level in sediment of the dental wastewater by application of the non-woven fabric filters A and B were 70% and 80%.The highest removal percentage was 95 % by using filter C. it was noticed that filter D (woven fabric filter) had removal percentage about 90%.
• Concerning the mean of removal percentage of mercury concentration level in effluent of the dental wastewater using the filter C (non-woven fabric filter) was recorded the highest removal percentage reaching 95%.
• The mean value of dental wastewater flow rate L/min through the proposed fabrics was high by using filter A and D giving 3.3, 2.7 L/min, respectively.
5-2 Conclusion:
from the study it can be concluded that:
• The basic filter can remove about 50% of the solids and mercury in the dental wastewater. The remaining amount must be removed by other developed technology.
• The application of the proposed fabric filters was found to be effective in removal upto 82% of total solids, 98% of suspended solids, and 97% of settleable solids.
• The proposed fabric filters was useful in decreasing the mercury concentration in both effluent and sediment of dental wastewater with removal percentage reaching 95%.
• All the non-woven fabric filter used (A, B and C) were effective in removal of solids and mercury especially filter C which isnon-woven polypropylene soft fabrics.
• filter D (woven silk) was found effective concerning removal of mercury, it was less effective in removal of settleable solids.
• Filter C which was considered as the slowest filter flow rate (0.16-0.32 L/min) in all proposed fabric filters.
5-3 Recommendations:
Based on the results of this study there are some recommendations to be implemented:
1. Application of the proposed fabric filters as a device to remove mercury from the already established dental units’ wastewater.
2. Construction of newly dental units designed with the proposed fabric filter (C).
3. Combination of woven and non-woven fabrics in the developed filter can achieve the best results concerning removal of most of solids and mercury.
4. Mercury free filling material such as composite.
5. Application of environmental law and simple guidelines for mercury waste handling will reduce the environmental concerns of dental waste to an insignificant level.
6. At a local level, it is recommended that the Egyptian Dental Association takes a lead role in training dental professionals to adopt the best practices for amalgam waste management in the dental setting.Implementation of protocols can be begin with training and awareness-raising and at a later stage, involve legislative control.
7. Development of interventional studies to evaluate the impact of different filter to remove mercury from the dental wastewater.
8. Encouragement of further researches to measure mercury concentration in wastewater, sludge and treatment plants to know the exact magnitude of the problem.