Gallery well application as a media for water treatment in flooded areas (case study: Morowudi Village, Gresik Regency)

High-intensity rainwater is known to cause flooding in Morowudi Village, Gresik Regency. This is a major issue for the local community because flood-related to water quality degradation renders it unfit. This study aims to apply gallery wells made as an alternative media to treat floodwater with better-quality water in Morowudi Village, Gresik Regency. In this research, there are two media variations: silica sand or building sand with a diameter of 0.2–0.4 mm applied in the form of a reactor with a diameter of 0.8 meters and a media thickness of 60 cm, which used a separation technique. The separation technique mechanism of the gallery well is SSF (Slow Sand Filtration). The floodwater percolates slowly through a gallery well reactor, with the influent water penetrating from the outside reactor and congregating in the wall as the effluent. The effectiveness of artificial gallery well application is measured by the reduction percentage of TDS, total turbidity, and total coliform. The results showed that artificial gallery well application reduces of TDS, total turbidity, and total coliform in floodwater at Morowudi Village. Thus, it can be used as usable water for the local community.


Introduction
Water is a fundamental and vital human need, so it must be adequately met to sustain life.Water is used for various activities, such as household consumption, industrial activities, and public places and places of worship [1].According to its function and designation, water is classified into two: clean water and drinking water.
Consumption and demand for clean water are directly proportional to the current density.The demand for clean water in Indonesia is very high, considering the extreme population density.Based on data released by Worldmeter, Indonesia's population in 2020 reached 273,523.615 million people, making it the fourth most populous country in the world.Data released by the Indonesian Central Statistics Agency (BPS) for 2020 states that clean water production has reached 5,262.1 million m3 for social, commercial, industrial, and other needs.BPS also stated that the achievement of clean water supply reached 72.55%.Even though there has been an increase in achievements compared to previous years, 27.45% of Indonesian people still need access to clean water.Meanwhile, the Sustainable Development Goals (SDGs) target for clean water supply is 100%.
The problem with the lack of clean water supply is that other problems cause scarcity of clean water, one of which is flooding.According to Law Number 24 of 2007, a flood is an event where water overflows in an area so that it disrupts and harms people's lives, both materially and healthfully.Flood disasters in Indonesia occur from year to year with fluctuating numbers.The National Disaster Management Agency (BNPB) noted that 2020 had the highest number of floods, with 1,518.The disaster resulted in death, suffering, disruption of access to education, decreased public health, and problems with access to clean water.When a flood occurs, the healthy water used by the local community will experience turbidity because it is mixed with sediment, making it unfit for daily use.
Every year Morowudi Village is affected by floods.In this case, flooding occurs when rainfall is not at its peak.Factors that influence the occurrence of flooding include the shape of the river, the capacity of the river that is too small, and the presence of buildings on the riverbanks.According to the testimony of residents, flooding can last for one week.There are several areas with different heights of inundation.Areas with the highest inundation can reach a height of 50 cm with an area of about 17%, areas with moderate inundation can reach a height of 20-50 with an area of around 19%, and areas with low inundation with a height of less than 2 cm with an area of 64%.This research will apply artificial gallery well technology to provide better quality water for use in daily needs.The media used to apply this gallery well are silica sand and building sand.Dug wells will be designed by combining slow sand filter criteria with a certain thickness to optimize performance in reducing pollutants.In addition, there is also a geotextile that functions as an initial filter and a container to refute the sand media so that it remains inside the wire mesh.

Study area
Morowudi Village is located in Cerme District, Gresik Regency, East Java.More precisely, this village is located south of the capital city of Gresik Regency and adjacent to Benjeng District.According to BPS Cerme District in 2021, Morowudi Village has an area of 2.52 km 2 with a percentage of the subdistrict area of 3.51%.The population of Morowudi Village reaches 4001 people, with a population density of 396.43 km 2 .BPS Cerme District for 2021 also informed that the highest rainfall in this area was in November, with an intensity reaching 298 mm and an average of 18.6 mm per day.It is known that every year Morowudi Village must experience flooding, which causes a cessation of clean water supply from the PDAM, which is the primary source of clean water for the residents of Morowudi Village, and this also contributes to a scarcity of clean water sources, which eventually becomes a particular problem for its residents.

Gallery well scenario
Based on the 2008 Indonesian National Standard (SNI), the slow sand filter method is filtering to separate solids and fluids with a tiny sand media diameter but with a high quartz content.Slow sand filter filtration has several advantages: low installation costs, simple operations, no need to add chemicals, and washing can be done only on the surface without backwashing [2].So instead of that, the application of the slow sand filter method in this study will be applied in the form of mock gallery wells and combined with wells made by the people of Morowudi Village, which will then be used as a source of clean water and used by local residents when floods occur.

Experimental design
The initial process of this research was carried out by taking flood water samples analyzed in the laboratory to determine the quality level of flood water with the parameters TDS, turbidity and total Coliform.Then the analysis process that shows flood water quality is carried out by setting clean water standards using Government Regulation 20 of 1990 concerning Water Pollution Control.The following process is manufacturing a gallery well reactor with an area diameter of 0.8 m and a height of 1 m.It is given geotextile on the outside along with wire mesh with a waterproof circle tarpaulin to prevent contamination from outside and as a container for treated water with two types of filter media: silica sand and building sand, each of which has a thickness of 60 cm and a media diameter between 0.2-0.4mm.
The gallery well reactor and this filtration technology were then applied to an artificial well located in a flooded area in Morowudi Village with the following steps: (a) The reactor will be assembled and placed in the planned flood area; (b) Flood water will flow through various sides of the reactor to the water reservoir in the middle of the reactor; (c) Furthermore, tests were conducted to determine turbidity and total coliform levels; (d) Processed samples are taken 3 (three) times; (e) After taking the first sample, drain it first before taking the second sample, as well as taking the third sample (Figure 1 and 2).

Data analysis
Processing and laboratory test processes are then analyzed from each experimental sample to analyze the effectiveness value on the parameters turbidity and total coliform to be processed according to the research objectives to get results and conclusions afterwards.The effectiveness value can be obtained using the following formula (Equation 1).(1)

Results and Discussions
In this study, the application of silica sand and building sand is used to process flood water through a filtration mechanism with a thickness of 60 cm.The sand media used is a type of sand with a 0.2 to 0.4 mm diameter.The input and output parameters tested in this study were turbidity and total coliform.This is done to determine how much effect the removal can produce, especially the total coliform by the schmutzdecke layer, which plays a role in the slow sand filter unit.
Figure 3 shows that the effectiveness of reducing turbidity resulting from the use of silica sand and building sand can be achieved by more than 99%.To find out the quality of water filtered by slow sand, the quality standard for clean water quality requirements of the Minister of Health Number 2 of 2023 concerning environmental health is used as a reference.It is known from Permenkes Number 2 of 2023 concerning environmental health that the maximum turbidity value in clean water for sanitation is 3 NTU per 100 mL sample.
Table 1 shows that the value of the average quality of processed water in this treatment is declared not to meet the requirements for clean water for sanitation.Therefore, efforts are needed to produce water that meets the clean water requirements for sanitation [3].This effort can be carried out by further processing, for example, the filtration process using membranes.
Based on the research results, the turbidity parameter has a high effectiveness value even though it does not yet meet the reference quality standard value.This is due to the high load received by the reactor, so many suspended substances still pass through the slow sand filter [4].As a result, the turbidity value in treated water still needs to meet quality standards.
The height of the filter media dramatically affects the removal of turbidity and head loss.The higher the filter media, the better the turbidity removal, but the resulting head loss will be more significant [5].This is because the higher the filter media, the more space between particles so that the particles trapped in the filter media will increase and the removal will be better.Figure 4 shows that the effectiveness of lowering TDS is deficient by less than 5%.To find out the quality of treated water, based on Permenkes Number 2 of 2023 concerning environmental health, the maximum TDS value for clean water for sanitation is 300 mg/L.Table 1 known that the TDS value of the average processed water in this treatment is declared not to meet the clean water requirements for sanitation.This is due to the use of sand in the filtration process [6]. Figure 5 shows the effectiveness of reducing the total number of coliforms reached more than 85% of a large number of bacteria.This is because the presence of geotextiles helps increase the number of bacteria, where this geotextile has a surface structure that is almost the same as the surface structure of a sand filter as well as its pores [7] so that filtered bacteria can grow on it.In addition, adding geotextiles can expand the surface area for the attachment of bacteria.This decrease indicates that the condition of the reactor is starting to undergo a clogging process so that in the thickened schmutzdecke layer, there is not only biomass but colloidal particles are also filtered out.In addition, bacterial competitors, such as protozoa which are also filtered, can inhibit the growth of bacteria in the schmutzdecke layer.Geotextiles help the performance of slow sand filter units [8].Geotextile fibers in the form of hydrophobic polymers allow microorganisms to adhere to surfaces that are not too flat.Therefore, a matrix in the form of mucus is formed to fill the spaces between the geotextile fibers.The continuous flow of water causes the thickness of the biofilm layer to form, causing the media pores to become clogged and increasing the decomposition products.Geotextiles made of PET or PP are hydrophobic, so suspended particles carried in raw water can trap microorganisms where the matrix formed between geotextile fibers is affected by variations in pore size [7].The existence of geotextiles is quite helpful in growing the schmutzdecke layer because of its sand-like structure, which can increase the number of bacteria in the filter bed [9].
Furthermore, many microorganisms and bacteria in the schmutzdecke layer also reduce turbidity [10].The schmutzdecke layer significantly removes contaminants because of a matrix formed from the excretion of microorganisms that grow and develop in the media [11].Water turbidity will be retained in the geotextile media and the schmutzdecke layer, which contains various kinds of microorganisms, so that the more microorganisms present in the schmutzdecke layer, the higher the efficiency of turbidity removal.In addition, the thicker the biofilm layer formed from microorganisms, the less surface area available for mass transfer, such as substrate or oxygen, into the biofilm.Biofilms consist of microorganisms and particulates that bind together and form a matrix of extracellular products.The

Conclusion
The Gallery well application using silica sand and building sand is known to reduce turbidity, TDS, and total coliform in flood water in Morowudi Village, Gresik.It is known that the effectiveness of reducing turbidity can reach more than 99%.While the level of effectiveness in reducing TDS is known to be less than 5%, and the effectiveness of reducing total coliform is known to be more than 85%.Nevertheless, processed water based on Permenkes Number 2 of 2023 concerning environmental health still to meet the quality standards for clean water for community sanitation. [8] Duran-Ros M, Puig-Bargués J, Arbat G, Barragán

Table 1 .
Input and output results.
J And Cartagena F R De 2009 Effect Of Filter, Emitter And Location On Clogging When Using Effluents Agric Water Manag 96 67-79 [9] Utari A W And Herdiansyah H 2020 Using Filtration As A Technology To Remove Pollutants In Domestic Wastewater Iop Conference Series: Materials Science And Engineering Vol 725 (Institute Of Physics Publishing) [10] Yaman C 2003 Geotextiles As Biofilm Filters In Wastewater Treatment [11] Rizki M H , D R P , Dan F N 2013 The Effectiveness Of Geotextile On Slow Sand Filter In Removing Pollutant The 4 Th Dan Widi Astuti International Seminar Department Of Environmental Engineering Department Of Environmental Engineering (Surabaya: Institut Teknologi Sepuluh Nopember) [12] Kusumawardani Y And Astuti W 2019 Efektifitas Penambahan Media Geotekstil Pada Saringan Pasir Lambat Terhadap Penyisihan Parameter Kekeruhan, Jumlah Coli Dan Cod Jurnal Teknosains 8 114 [13] Hamidah N L , Dan T Y 2012 Studi Komunitas Bakteri Pada Lapisan Schmutzdecke Dalam Slow Sand Filter Dengan Variasi Berbagai Media Tumbuh Thesis (Surabaya: Institut Teknologi Sepuluh Nopember) [14] Campos L C, Su M F J, Graham N J D And Smith S R 2002 Biomass Development In Slow Sand Filters Water Res 36 4543-51