The Utilization of Bacillus Subtilis Bacteria to Improve the Mechanical Properties of Concrete

The utilization of concrete as a building material is well-known worldwide and increasing continuously due to its sustainability, low maintenance cost, durability, performance, etc. The ingredients of concrete, its constructional methodology, and exposure conditions have been observed to be moderating and improving daily but the focus of this research is on the laboratory investigation of Bacterial Concrete which is the technology established on the application of the mineral producing microbes like Bacillus subtilis which have the properties of bio-calcification and the ability to precipitate CaCO3 effectively inside concrete structures. This CaCO3 precipitation is able to fill the pores and cracks internally and this subsequently makes the structure to become more compact. Nutrient Broth (NB) media was employed for the growth and spore formation of Bacillus subtilis bacteria in this experimental study and four different bacterial culture densities including 0.107, 0.2, 0.637, and 1.221 were estimated at OD600 and directly added to the concrete matrix using the previously fixed water to culture ratio of 0.5:0.5. Moreover, 100 mm cubical concrete specimens were cast, subjected to compressive and tensile strength tests for different curing ages, and finally compared with Conventional Concrete with OD600=0. A significant increase was observed in the mechanical strengths due to the addition of Bacillus subtilis bacteria in concretes with a culture density of 0.637. Furthermore, cylindrical concrete specimens with 100 mm diameter and 200 mm height were prepared for Ultrasonic Pulse Velocity (UPV) analysis and the results showed specimens prepared with culture density of 0.637 have higher pulse velocity than other microbial groups. A UPV vs. compressive strength relationship curve was, however, later proposed for different strengths of concrete

The Influence of Jogjakarta Outer Ring Road Development Plan on the National Roads in the Special Region of Yogyakarta

The Influence of Jogjakarta Outer Ring Road Development Plan on the National Roads in the Special Region of Yogyakart

Acceptance Analysis of PDAM Sleman’s Water Tariff, Based on Revenue and Willingness to Pay Projection

In Sleman, the Regional Water Company (PDAM) provides clean water to the community and charges a tariff for each cubic meter of water sold to customers. According to the Minister of Home Affairs Regulation No. 71 of 2016 states, PDAM tariffs requiring an annual review in November. The most recent tariff was set by PDAM Sleman in 2016, therefore, a recalculation is required. In addition, there is a need to analyze the tariff acceptance from the service provider, and service recipient’s point of view. In this study, the calculation tariff method utilized a formula based on the Minister of Home Affairs Regulation No. 71 of 2016. Meanwhile, the acceptance analysis from profit point of view conducted by calculating the projection of water sales revenue, profit to earning assets ratio, and customer willingness to pay (WTP). Furthermore, revenue projections were obtained by multiplying tariffs with the water sold volume, while the WTP projection is obtained using the inflation method, based on the PDAM Sleman customers’ wTP, from the 2007’s research. PDAM Sleman tariffs based on calculations resulted in low tariffs of IDR3727.48, basic tariffs of IDR4659.36, and full rate of IDR9460.17. Based on the WTP analysis, the tariffs are feasible from the service recipient’s (PDAM customers) point of view, because this is affordable by customers, for the average water consumption. However, from the service provider’s (PDAM Sleman) point of view, the tariffs are not feasible a 0.31% profit ratio is much lower, compared to the 10% profit ratio. Therefore, tariff adjustments are required to increase profits. These strategies include determining tariffs based on consumption blocks alone, without breaking down based on customer group categories and adjusting the second and third consumption blocks’ rate

Analysis of the Carrying Capacity and the Total Maximum Daily Loads of the Karang Mumus Sub-watershed in Samarinda City Using the WASP Method

Watershed is a multi-aspect ecological system, which functions as a source of water resources, in order to meet daily needs. It also motivates both economical and life matters, as well as serve as a sanitary channel for the surrounding community. Watershed also generates pollutants, which are known to potentially cause a decrease in river water quality. The degradation of river habitats that are caused by high pollutants penetration into the water body, decreases the capacity to carry out self-purification of toxic loads. The water pollutant load-carrying capacity is then calculated through various methods, one of which is the use of a computerized numerical modeling simulation called WASP (Water Quality Analysis Simulation Program). This method was developed by the ES-EPA, in order to process TMDLs (Total Maximum Daily Loads) data on river bodies, as well as examine each part of the water quality, based on spatial and temporal inputs. This study was conducted at the Karang Mumus Sub-watershed flowing through the centre of Samarinda City, with aims to determine the pollutants' carrying capacity, existing load, and toxic waste allocation, via the use of the BOD (Biological Oxygen Demand) technique as a parameter of water quality. The calculation was carried out by segmenting the river into five parts, based on the number of districts it passes through, during pollutant loads inventory. The WASP modeling simulation showed that the total pollutant load-carrying capacity of the whole segments was 5,670 kg/day. It also showed the existing loads of about 3,605 kg/day, with the margin having the ability to receive pollutants at 2,065 kg/day. Moreover, the allocation of pollutant loads varies for each segment, with 2, 3, and 4 observed to reduce the pollutant by 390, 220, and 10 kg/day, respectively. However, segments 1 and 5 were still allowed to receive pollutant loads up to 1,740 and 945 kg/day, respectively

Effect of Well Resistance on Time Factor Ratio Due to PVD Deformation

One of the most common soft soil enhancement techniques used to expedite the consolidation time significantly is Prefabricated Vertical Drains (PVD). This technique needs a sufficient discharge capacity value because it primarily functions as a drainage channel. The deformation of PVD is considered as one of the primary factors which affect discharge capacity. Therefore, this research determined the influence of upper-side deformation on PVD's discharge capacity (qw) using a specific design apparatus known as ASTM D4716, which manages the determination of transmissivity and flow rate at the longitudinal direction of geosynthetics. Furthermore, two PVD samples with dimensions of 3 and 4 mm thickness, 100 mm width, and 1000 mm length were examined under straight and buckled conditions. Stepwise confining pressures from 50 to 200 kPa were subjected to the samples under hydraulic gradients with values of 0.2, 0.5, and 1.0. The results showed that samples with greater thickness had higher discharge capacity, which significantly reduced in the lower hydraulic gradient. The deformation on the upper side of PVD induced a decrease of discharge capacity by approximately 13-16%, which led to a delay in the consolidation time. The discharge capacity values obtained from the experiments were employed as parameters in a time factor ratio of Th,w/Th. The analysis results show that the buckled PVD has a more considerable consolidation time due to the increase in the Th,w/Th ratio, with a discharge capacity value below 10-4 m3/s. It can be concluded that the deformation in the form of buckled conditions on the upper side of PVD had a considerable impact on PVD effectiveness

The Utilization of Soybean as a Catalyst Material in Enzyme-Mediated Calcite Precipitation (EMCP) for Crack Healing Concrete

The effect of using soybean as a catalyst in the Enzyme-Mediated Calcite Precipitation (EMCP) method of crack healing concrete is discussed in this research. The existence of cracks in concrete reduces its quality, therefore, there is the need for repair efforts and one of these is through injection using the EMCP method. This technique employs the plant-derived urease enzyme to catalyze the reaction between calcium chloride (CaCl2) and urea (CH4N2O) towards precipitating calcium carbonate (CaCO3). Its effectiveness was, however, evaluated using a test tube experiment, and the optimum combination of urease, urea, and calcium chloride was selected and used as the preliminary data for the soybean added as a catalyst. Meanwhile, the concrete samples were prepared in the form of 5 cm x 10 cm cylindrical concrete and the crack was made through Universal Testing Machine (UTM) with a controlled area observed to be in the range of ± 0.2-0.3 mm. The injection solution was added to the concrete using the percolation method up to the period the height of the solution was 5 mm above the concrete surface and this was conducted several times with the effect on the concrete cracks evaluated through permeability tests which were used as one of the concrete quality parameters. Moreover, the permeability coefficient value was found to be inversely proportional to the quality and this means a smaller value of the coefficient produced better concrete quality and vice versa. The results showed the total calcite formed in the sample after the 4th injection was 18.3% of the total surface area of the concrete crack and was able to reduce the concrete permeability value by 95.43%. This, therefore, means the use of soybean in the EMCP method is considered feasible to repair concrete cracks

Regional Frequency Analysis of Rainfall, using L-Moment Method, as A Design Rainfall Prediction

Frequency analysis is a method for predicting the probability of future hydrological events, based on historical data. Generally, frequency analysis of rainfall data and discharge data is performed using the moment method, but this method has a large bias, variant, and slope, thus there is a possibility of producing inaccurate hydrological design magnitudes. Meanwhile, the L-moment method is a linear combination of Probability Weighted Moment, with the ability to process data concisely and linearly. This study was therefore conducted to discover the L-moment method’s capacity to obtain a regional probability distribution and design rainfall, used as a basis for calculating hydrological planning, in anticipation of disasters. The study location, Mount Merapi, was selected to enable a more accurate prediction of maximum rainfall with the capacity to cause cold lava in the area, and consequently, reduce the risk of loss for people living within close proximity. According to the results, the L-moment regional ratio results were τ2R = 0.203, τ3R = 0.166, and τ4R = 0.169. The homogeneity and heterogeneity tests show all rainfall stations are uniform or homogeneous, and no data were released from the discordance test results. Also, the growth factor value increases in each return period design rainfall prediction. In this study, the suitable regional probability distribution for the research area is the Generalized Logistic distribution with formulated design rainfall equation. Regional design rainfall is able to predict possible rainfall within the area. The Test model showed the minimum RBias = 0.45%, maximum RBias = 41.583%, minimum RRSME = 0.45%, and maximum RRSME = 71.01%. Meanwhile, the L-moment method’s stability was shown by the model test minimum error = 1.64% and maximum error = 16.60%. The higher error value in the higher return period shows L-moment is able to reduce bias data, however, this has limitations in the higher return period

Influence of Pre-Stressing on Tieback Retaining Wall for Sandy Soils Excavations

Pre-stressed ground anchor systems or tieback systems are commonly used at wide and irregular-shaped excavations, with the advantage of lower cost and ease of construction compared to the braced excavations, but they come with the drawback on permits for excavations near buildings and tunnels. Research on tieback systems in sands was generally conducted. However, the studies on the correlation between the retaining wall deflection and pre-stress force are few. The objectives of this paper are to study the influence of pre-stress force, depth of excavation, wall embedment length, and soil shear strength that is represented by soil friction angle on the deflection and soil pressure acting on the retaining wall. The parametric study was conducted on an excavation in sand using the finite element method with the Hardening soil model. The results showed that a 50 kN/m increase in pre-stress force reduced the wall deflection on top of the wall by 0.005–0.083% of excavation depth. However, the pre-stressing influence in reducing wall deflection at excavations became less significant along with the sand density increase due to higher friction angle contribution to excavation stability. Moreover, the pre-stress force needed for stabilization of the wall with long embedment length is smaller than those on the wall with shorter embedment length, since the embedment length increase of 0.25 times of excavation depth reduces wall top deflection by 0.002–0.095% of excavation depth. Also, the increase of soil density reduces the need for wall embedment length, so at dense sand, the embedment length of 0.5 times of excavation depth is sufficient to support the excavation

Determination of Optimal Rain Gauge on The Coastal Region Use Coefficient Variation: Case Study in Makassar

The quality of rainfall data is highly significant in disaster analysis, ecology, and water resource management. However, the accuracy and quantity of rain gauges are often inadequate, especially for analyzing extreme events, including the Makassar City flood, in 2019. This inadequacy is due to several reasons, including rain gauges’ inadequacy and insufficient distribution. This study, therefore, aims to analyze the requirements of optimal rain gauges, using coefficients of variation in various error levels, based on the latest rainfall data in several locations within Makassar City. Monthly and yearly rainfall observation data from 2010 to 2019 obtained at 5 locations were used to calculating the optimal rain gauge number. According to the results, the existing station has a 10% and 15% monthly and annual error, respectively. This region has 3 groups causing highly optimal rain gauges, and these are the first group comprising Paotere, Panaikang, as well as Biring Romang, while the second and third groups comprise Sudiang and Barombong. The northwest wind blows towards the coast and crosses these three places in a line, thus, causing rainfall intensity with a slight disparity, between the first group. Furthermore, the combination of these places resulted in low optimal rain gauge. However, the combination of the first group with the second and third lead to an increase in the optimal rain gauge number. The low elevation, proximity, and location of the first group’s three locations in line with the rain-causing wind results in low optimal rain gauge. In the combination of the first, second, and third groups, additional gauges are required to obtain a 5% or 10% error. The rainfall intensity and position greatly influence the rain catchment in Makassar, and consequently, the optimal rain gauge number. In addition, the distance, topographical aspects, and the combined land-sea and monsoonal winds’ factors must also be analyzed, in deploying equipment

Feasibility Evaluation of Wastewater Treatment Plant System: A Case Study of Domestic Wastewater System in Sleman Regency, Yogyakarta, Indonesia

Domestic Wastewater Treatment Plant (DWWTP) type 1 and DWWTP type 2 were being evaluated. DWWTP type 1 is located in Sembir area while DWWTP type 2 is located in Tambakrejo area which are both in Sleman Regency, Special Region of Yogyakarta (Daerah Istimewa Yogyakarta or DIY), Indonesia. The emphasis of this research is to choose the manhole material which has the least leakage to the soil, influent discharge performance and wastewater treatment quality effluent. The method used to measure the discharge was by averaging daily discharge for twelve hours, while the E. Coli bacteria under the manhole was also being analyzed. Pollution Index method was also used to evaluate the pollution levels of the wastewater treatment effluent. Results of the study indicated that DWWTP type 1 performance was not optimal because the number of users was greater than that of the design. The impacts were excessive capacity, improper detention time and several parameters of the effluent did not meet the Indonesian legal regulation, including Chemical Oxygen Demand (COD), with efficiency of 34.43%. Wastewater treatment quality effluent parameters which met the Indonesian legal regulation were pH, TSS, TDS, Oil and Grease and Chlorine for DWWTP type 1. Pollution Index (PI) of DWWTP type 1 was 7.02 and PI of DWWTP type 2 was 6.96 which were relatively categorized as moderately polluted. DWWTP type 2 performance was optimal with mean discharge lower than the design discharge. Parameters of the effluent which met the Indonesian legal regulation were pH, TSS, TDS, Oil and Grease, Detergent and COD for DWWTP type 2. The COD of DWWTP type 2 met the Indonesian legal regulation with high efficiency of 73.24%. The E. Coli bacteria was not found in soils under the ring type precast concrete manholes. Hence ring type precast concrete base manhole is recommended