The integrated monitoring system of water quality is eminently reliant on water quality trend data. This study aims to obtain water quality patterns related to land-use change over a periodic observation in the Opak sub-watershed, Indonesia, both from a seasonal and spatial point of view. Landsat image data from 2013 to 2020 and water quality data comprising 25 parameters were compiled and analyzed. This study observed that land use remarkably correlated to water quality, especially the building area representing the dense population and various anthropogenic activities, to pollute the water sources. Three types of pollutant sources were identified using principal component analysis (PCA), including domestic, industrial, and agricultural activities, which all influenced the variance in river water quality. The use of spatiotemporal-based and multivariate analysis was to interpret water quality trend data, which can help the stakeholders to monitor pollution and take control in the Opak sub-watershed. The results investigated 17 out of 25 water quality parameters, which showed an increasing trend from upstream to downstream during the observation time. The concentration of biological oxygen demand over five days (BOD₅), chemical oxygen demand (COD), nitrite, sulfide, phenol, phosphate, oil and grease, lead, Escherichia coli (E. coli), and total coli, surpassed the water quality standard through spatial analysis.

The Special Region of Yogyakarta is one of the provinces in Indonesia with a large number of communal wastewater treatment plants (CWWTPs). However, less than 40% of CWWTPS in the province are able to be operated well. This study aims to determine the effectiveness of CWWTPs concerning the quality of the surrounding groundwater. The research location was in Mlati, one of three sub-districts with the highest number of CWWTPs and highest population density in the province. Technical data were analyzed in a laboratory, including water quality of CWWTPs and groundwater quality. This study also analyzed non-technical data related to CWWTP management. These data were collected through in-depth interviews with CWWTP managers and users. The data were analyzed systematically, not only quantitatively but qualitatively. The distribution of water quality from CWWTP treatment and groundwater was mapped using inverse distance weighting (IDW). The results show that the CWWTP effluent meets quality standards for pH, temperature, COD, oil and grease, and ammonia. However, some CWWTPs fail to meet the quality standards for the TSS and E. coli parameters. Groundwater has an acidic pH, with ammonia, nitrite, and zinc parameters meeting quality standards, but oil and grease, COD, nitrate, and Pb concentrations exceed quality standards in several wells. This study indicates that the presence of CWWTPs is not correlated with the quality of groundwater due to the inefficiency of the CWWTPs, the unmet coverage area, and the conditions of sanitation facilities at the location.

LPG gas is the main fuel used in households. These days LPG gas leak triggered an accident that resulted in huge losses, especially if the accident occurred within the dense housing. LPG gas leakage monitoring and early detection of a gas leak and a leak warning is needed to prevent more fatal accident. Wireless sensor networking is a technology that can be used to build a centralized monitoring system by using a microcontroller as the interface and control system. This research developed system device monitoring and early detection of gas leaks by utilizing gas sensors MQ-4 and AVR microcontroller family as control devices. The system is also equipped with XBee PRO S2B nirkable devices as the interface to the wireless networking system that is used to transmit sensor data from the detection point to the monitoring center equipped with a PC and software integrated Visual Basic. Gas leak alert is sent with the message formats through social networking Gtalk.

Communal wastewater treatment plant (CWWTP) has been chosen as one system to treat domestic wastewater due to simple technology, flexible management, and cost-effectiveness. There are 376 CWWTP have been recorded by Environmental Agency of Yogyakarta (DLH DIY) that spread in five regencies. Monitoring results on CWWTP effluent showed that some physical and chemical parameters did not meet the domestic wastewater standard. Therefore, evaluation of removal efficiency in terms physical and chemical parameters are necessary. The samples were collected from nine CWWTP in Banguntapan, Bantul and Gamping sub-districts. The physical and chemicals parameters (pH, TSS, BOD, COD, Ammonia, oil, and grease) of influent and effluent from CWWTP are analyzed based on National Standard of Indonesia (SNI) for domestic wastewater. The results show that BOD (>70%) and TSS (>50%) have better removal effectiveness compare with COD, ammonia, oil, and grease (40%). Overall, CWWTP in Banguntapan subdistrict has better performance compare with CWWTP in Bantul subdistrict.

Carbon monoxide (CO) is an odorless, tasteless and colorless gas in which it is difficult to be recognized by human beings. CO gas that enters the human body at a certain concentration has negative impact on health. A monitoring system which can recognize the amount of CO gas concentration, especially for the indoor is needed to cope with this problem. In this paper, monitoring system is designed using XBee as a data transmission medium. Three XBee are integrated with the sensor node circuits, microcontroller as a data processor and one XBee as a data collector. The sensor nodes consist of an LM35DZ temperature sensor, a humidity sensor HSM 20-G and a CO sensor TGS 2600. The data are read by sensor nodes and then they are transmitted wirelessly using XBee. The data collector functions as the receiver, processor and data viewer in the form of tables and graphs using Visual Basic 6.0. From this design, the results of data transmission can be displayed in the form of graphs and tables which are then stored into the database. The data transmission range is ± 53 meters indoor, where the average error TGS 2600 sensor reading is 4.414 %.

An assessment of aerobic granular sludge (AGS) in a bubbled airlift continuous reactor (BACR) was done to determine the AGS growth kinetics in the continuous reactor and the impact of varied hydraulic retention time (HRT) against the AGS structure. Sodium acetate was used as the sole carbon source with a 100:20 ratio of COD/N synthetic water. The system was operated at five variations of HRT, i.e. 12, 10, 8, 6, and 4 hours, with organic loading rate (OLR) ranging from 1.6 to 4.8 g COD/day in the BACR. Organic removal decreased from 73% to 52%, along with the increment of OLR, while HRT decreased from 12 hours to 4 hours. The kinetics of organic removal in the BACR were examined to get a better understanding of organic removal trends by AGS in a BACR. The models used for biomass growth analysis were the Monod, Contois, Grau second-order, and Stover-Kincannon kinetic models. This study showed that the best suited models for organic removal in BACR were the Grau second-order kinetic model with an a value of 0.1382 and a b value of 1.0776, and the Stover-Kincannon kinetic model with an Rmax of 5.8 g COD/L.day and a KB of 6.24 g COD/L.day.