Performance of black stone waste (BSW) as a substitute for natural coarse aggregate in concrete production has been studied concerning the unit weight, compressive strength and splitting tensile strength. The concrete mixtures were designed using a weight ratio of 1 Portland Pozzolan cement: 2 fine aggregate: 3 coarse aggregate and water cement ratio of 0.5. Five concrete mixtures were made by replacing natural coarse aggregate in concrete mixtures with BSW of 0%, 25%, 50%, 75%, and 100%. For each mixture 10 specimens were made: 5 cube specimens measuring 150x150x150 mm for compressive strength test and 5 cylindrical specimens with a diameter of 150 mm and 300 mm high for splitting tensile strength test. For measurement of unit weight, the two types of specimens were used. The result shows that the unit weight of concrete made with BSW is about 3%-7% lighter than that of concrete made with natural coarse aggregate. Concrete made with certain quantity of BSW can produce both compressive strength and splitting tensile strength higher than concrete made with natural coarse aggregate. The compressive strength and splitting tensile strength of concrete made with 100% BSW can respectively reach about 88% and 104% of that of concrete made with natural coarse aggregate. Keyword-Black Stone Waste, Unit Weight, Compressive Strength, Splitting Tensile Strength I. INTRODUCTION Concrete is a very popular construction material used in the construction industry. This is because concrete is easy to make, strong withstand compressive loads, durable and the price is relatively cheaper than competing construction materials, such as steel. The performance of concrete is much influenced by the forming material: water, cement and aggregate, so that the selection of the material must be considered carefully in order to obtain the quality of the concrete as designed. The use of aggregates, fine aggregate and coarse aggregate, in concrete production can reach about 75% of the total material needed [1]. Thus the selection of the type of aggregates used must be well controlled, particularly with regard to their properties. Black stones are basalt stones which origin from volcanic lava having frozen. This type of stone is blackish in color, sharp and rough. In the Province of Bali, black stones are usually processed by carving craftsmen to be used as traditional building ornaments. Approximately 30% of black stones processed by craftsmen becomes waste, in the form of granules or powder. At present, this waste has not been managed properly and is usually left to accumulate around the working area and/or drainage channels, so that it has the potential to cause environmental disruption. Figure 1 shows the waste around the craftsmen working area.

The provision of clean water is still a very serious problem in some places. Many times, water is available in abundant quantities but the quality does not meet human needs. On the other hand, there is a lot of locally available raw materials available for producing ceramic filters which in turn can be used to produce clean water from polluted water. The wild and domesticated fern grows widely in Southeast Asia. The stem can be used as the carbon material for producing filters. This study aims to utilize the fern stem as indigenous material to produce an affordable, easy to use, robust clay base water filter for the less advantaged communities. Chopped fern stem mixed with clay in several compositions (50%, 60%, 70%, 80%, 90% clay), shaped to produce 2 cm thick biscuits with 10 cm diameter, and dried for one week at room temperature and then fired at 9000C overnight. It was found that biscuits with 50% and 60% clay can be used as filters and filter with 50% clay produced filtrate with a better quality which meets the Indonesian standards for class two water which is water for drinking but not potable water. Therefore the fernstem is a potential raw material for ceramic filter production.

Abstract. Ciawi Y, Inabuy FS, Teriyani NM, Ramona Y. 2023. Potential of sodium dichromate and sodium silicate to control in vitro growth of Bacillus cereus, a metal corrosion-causing bacterium. Biodiversitas 24: 1530-1537. The maintenance cost of metal-based objects in industrial and construction sectors has been found to significantly increase due to corrosion. Most corrosion is caused by metal oxidation, and about 2% of this corrosion is induced by microbial activity (MIC). The main objectives of this research were to isolate, and identify corrosion-causing bacteria, and to find out the optimum concentration of sodium dichromate and sodium silicate to control their growth in vitro. These compounds have been used to protect the metal surface from corrosion caused by non-microbial-induced corrosion. Three different bacterial isolates were obtained in this study and the black colony (the predominant isolate) was further investigated in the determination of their optimum inhibitory concentrations. Application of sodium dichromate and sodium silicate at the rates of 0.1% w/v and 2% w/v, respectively were found to be optimum to inhibit the in vitro growth of this black bacterial isolate in our study. The predominant isolate found in our study was identified as Bacillus cereus, following the alignment of its 16s rDNA sequence with those deposited at the GenBank (NCBI). Additionally, Enterobacter asburiae was also found on the surface of corroded water tanks.

The soil is an important material for human life. The problem that is often encountered with soil is soil contamination due to the discharge of leachate into the soil. This research aims to observe the influence of leachate viscosity on seepage using Geo-Studio SEEP/W Program. The samples of leachate were taken from ceramic industry and from Suwung landfill site. Soil samples were silty sandy taken from Ida Bagus Oka street, Denpasar, Bali. Seepage modeling in Geo-Studio SEEP/W was conducted on silty sand condition using pure water (without leachate), leachate from ceramic industry, and leachate from Suwung Disposal Site. Seepage modeling on Geo-Studio was conducted on saturated/unsaturated condition. It was found that the leachate viscosity was different each other. The viscosity of leachate from ceramic industry was 0.01366741 N s/m 2 and 0.002061309 N s/m 2 from Suwung Disposal Site. Due to mixed with leachate, soil hydraulic conductivity decreased from 0.001949 cm/s to 0.0001029 cm/s. The largest discharge and velocity of seepage on silty sand material from Ida Bagus Oka street, Denpasar, obtained by using Geo-Studio SEEP/W Modeling was produced by pure water (without leachate), whereas, the smallest one produced by leachate from Suwung landfill site. The influence of seepage discharge and seepage velocity change on silty sand in Ida Bagus Oka street, Denpasar due to the flow of leachate from ceramic industry and leachate from Suwung Disposal Site against pure water seepage discharge and seepage velocity are 70,573% and 5,313%.

Tukad Badung is the major river flowing through Denpasar, the capital city of Bali Province, Indonesia. It is polluted by domestic dan industrial waste which is contributed by surrounding communities such as hotels, shopping area, animal husbandry, printing industries, tofu and tempeh industries industry, and housing area. This research aims to analyse the quality of the water and determine the best among options provided to overcome the pollution problem conducted by using two analytical programs, i.e. QUAL2Kw and Analytical Hierarchy Process (AHP). According to the results of QUAL2Kw analysis, several parameters of water quality of Badung River did not meet the Indonesian standards of water quality stated in Regulation Number 82 the Year 2001 about Water Quality Management and Water Pollution Control. The TSS reached 111.02 kg/day, the BOD reached 92.24 kg/day, and the COD reached 440.92 kg/day. Whereas the pollution load capacity is only 15.43 kg/day for TSS, 19.68 kg/day for BOD, and 7.45 kg/day for COD. This problem occurred was due to the home industries activities in the upstream part of the Badung River. The result of the Analytical Hierarchy Process (AHP) shows that “improving monitoring and supervision of waste disposal” has the highest composite weight value of 0.317. Among a series of solutions offered, this result suggests that the local government should take actions to impose the regulations on wastewater disposal to the river stream by surrounding communities especially the small and middle-size enterprises.