This study reports the use of sewage sludge generated from sewage treatment plant (STP) as raw material in a clay brick-making process. The physico-chemical and mineralogical characterization of the sewage sludge and clay were carried out in order to identify the major technological constraints and to define the sludge pretreatment requirements if necessary. Moreover, the effects on processing conditions and/or on changes of typical final characteristics are also evaluated. Bricks were produced with sewage sludge additions ranging from 10 to 40% by dry weight. The texture and finishing of the surface of sludge-amended clay bricks were rather poor. As for the physical and chemical properties, bricks with a sludge content of up to 40 wt.% were capable of meeting the relevant technical standards. However, bricks with more than 30 wt.% sludge addition are not recommended for use since they are brittle and easily broken even when handled gently. A tendency for a general degradation of brick properties with sludge additions was observed due to its refractory nature. Therefore, sludge bricks of this nature are only suitable for use as common bricks, which are normally not exposed to view, because of poor surface finishing.
Bricks produced from sewage sludge in different compositions were investigated. Results of the tests indicated that the sludge proportion is a key factor in determining the brick quality. Increasing the sludge content results in a decrease in brick shrinkage, bulk density, and compressive strength. Brick weight loss on ignition was mainly due to the contribution of the contained organic matter from the sludge being burnt off during the firing process, as well as inorganic substances found in both clay and sludge. The physical, mechanical, and chemical properties of the bricks that were supplemented with various proportions of dried sludge from 10 to 40 wt% and generally complied with the General Specification for Brick as per the Malaysian Standard MS 7.6:1972, which dictates the requirements for clay bricks used in walling in general. A standard leaching test method also showed that the leaching of metals from the bricks is very low.
Turbid surface water was treated using a pilot scale water treatment plant comprising coagulation, flocculation, sedimentation and rapid gravity filtration, using Moringa oleifera seeds/alum as coagulants. Turbidity removal of M. oleifera, alum, and the mixture of both M. oleifera/alum were compared, and results obtained were 7.2, 4.2 and 3.2 NTU, respectively. The turbidity achieved using M. oleifera/alum mixture and alum were less than the required standard of 5 NTU, while M. oleifera/alum mixture recorded the least turbidity value (3.2 NTU) with removal efficiency of 99%. The natural alkalinity of the water did not vary during the treatment processes. Therefore M. oleifera/alum mixture could be considered as a suitable alternative for partial replacement of alum as coagulant in surface water treatment, which is an added advantage since M. oleifera is a natural product with less or no side effects as compared to alum as a chemical agent.
Malaysia, like any other country has experienced a number of chemical accidents in the past, hence the necessity to undertake thorough consequence analysis to mitigate similar occurrences in future. The water treatment plant in question keeps more than 18.6 MT (metric tonnes) of chlorine to disinfect water for the community in municipal area. However, chlorine is a hazardous chemical that can cause serious injuries, loss of life and damage to properties and environment if not handled properly. Hence using the Environmental Protection Agency (EPA) methodology an offsite consequence analysis was conducted to determine the potential impacts in the event of catastrophic release of chlorine at the water treatment plant. A "worstcase release scenario" and "alternative scenario" were developed for the treatment plant. The results obtained from the use of TRACE software showed that a potential hazard exists, even under average annual weather conditions. Within a 6 km radius, an estimated number of 102 000 people within the zone for a 3 ppm chlorine exposure may be affected due to a worstcase release. The consequence isopleth for the respective chlorine concentration indicates that the chlorine plume is directed towards the administration building and process unit facilities of the plant. Hence, it is critical to ensure that all personnel within the plant are provided with sufficient training on the emergency response plan and the application of the relevant personnel protective equipment (PPE) in the event of accidental releases. Although the hazard exists, the risk to the public may be low. An alternative release scenario would be limited due to the use of safety and mitigation systems incorporated into the chlorinating system, but the plant requires other supporting safety measures to supplement the existing facility's inherent safety. Such measures are essential to ensure that in the event of a potential incident at the plant onsite and offsite effects could be minimised to ensure the risk is as low as reasonably practicable (ALARP).
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