DOMESTIC WASTEWATER PIPING NETWORK PLANNING AND TECHNOLOGY RECOMMENDATIONS FOR WASTEWATER TREATMENT CASE STUDY: THE AMBARITA AREA, SAMOSIR REGENCY, NORTH SUMATRA

Lake Toba is one of ten programs the Ministry of Tourism in the Republic Indonesia, as a priority tourism area because of its unique potential. The Ambarita is one of 16 villages that are priority areas in Simanindo Subdistrict, Samosir Regency. At present, the quality of Lake Toba's waters has been polluted, the pollution is caused by domestic waste water which is discharged directly without prior treatment. The purpose of this study is to plan a domestic wastewater pipeline network and recommendations for wastewater treatment plants with a centralized system in the Ambarita. This study uses a quantitative data analysis method by using a population projection approach with maximum capacity to be planned in the draft MasterPlan of Ambarita and literature study for WWTP technology recommendations. The results showed that the total discharge of wastewater in the Ambarita was 0,06495 m3/second and the results of laboratory tests showed the parameters that exceeded quality standard were free chlorine and fecal coli. Piping network planning in the Ambarita uses concrete type pipes with diameters of 100 mm, 125 mm, 150 mm, 200 mm and 250 mm. The selected Waste Water Treatment Technology recommended is anaerobic-aerobic biofilter technology with removal efficiency for fecal coli and free chlorine are 99.9% and 65%.


INTRODUCTION
Lake Toba is a volcanic lake located in North Sumatra. The potential for the uniqueness of Lake Toba is that there is an island in the middle of the lake called Samosir Island so that its uniqueness makes Lake Toba one of the ten programs of the Ministry of Tourism Republic Indonesia, as a priority tourist area. According to the President of the Republic of Indonesia, Lake Toba has 28 tourist points that can be developed into world-

RESEARCH METHODS
The pipeline network planning and recommendations for domestic WWTP are carried out based on the results of several field applications that are in accordance with existing conditions. This research was conducted in the Ambarita area, Simanindo District, Samosir Regency, North Sumatra from December 2019 to February 2020. Sources of data used in this study come from primary data, namely the amount of wastewater, sources of wastewater, conditions of MCK, WWTP, soil elevation and documentation to support the research, while secondary data includes topography, lake water quality parameters Toba, population, average water consumption, location map. The method used in this research is using a descriptive quantitative data analysis method in designing and recommending domestic WWTP (Nasoetion et al., 2017). The stages of the research method as a whole can be seen in Figure 1.

Figure 1. Research Flowchart
The calculated and analyzed data is processed to obtain a domestic wastewater pipeline network design and a recommendation for WWTP technology using the following methods:

A. Population Projection
Indonesia is the fourth country with biggest population in the world (Sari, Madonna, et al., 2018). The calculation of population projections will affect domestic clean water needs. The population projections of the Simanindo Priority Area are divided into 2 types, namely natural projections and progressive projections. Natural projection is a natural population growth projection which has not been influenced by external factors that will affect population development in the area. Meanwhile, a progressive projection is a population projection that looks at population development if population migration is expected to support. Unfortunately, high population density can lead to natural disaster and disturbed ecosystem balance (Sari, Sugiana, et al., 2018).
There are several methods that can be used to analyze the development of natural population, namely: To determine the most appropriate method to be used in planning, it is necessary to calculate the correction factor, standard deviation, and the state of future developments in the city. The correlation, r, can be calculated using the formula: Annotation: R 2 = Correlation factor Pn = Total population at year n Pr = average population of known data P = Projected population based on calculations the regression method done The correlation criteria are as follows: 1. r < 0, strong correlation, but negative value and relationship between the two variables is inversely proportional. 2. r = 0, both data have no relationship.
3. r > 1, strong correlation, positive value and the relationship between the two variables is directly proportional.
The standard deviation can be calculated using a formula: n P -Pn n STD = n Annotation: STD = Standard deviation of known data n = Amount of known data The projection method chosen is the method with the lowest standard deviation value and the largest correlation coefficient.

B. Need for Clean Water a) Domestic Water Needs
Domestic water needs are met in two ways, namely House Connections and Public Taps. For now, the Ambarita area still serves the planning area at 0%. It is planned to increase to 91%. Based on data (Badan Pusat Statistik, 2018), the existing population of Ambarita in 2018 is 1043 people and is included in the rural category. The ratio between the number of residents served by Domestic Connection and Public Taps for rural areas is 70:30. Standard drinking water needs of: -Home connection: 100L / person /day -General faucet: 30 L / person / day The calculation of domestic water demand can be seen in the equation below (Fatimah et al., 2014).

Domestic Water Need = Total Population x Water Needs per Capita
Per capita water needs will differ in each city depending on the social and economic level of the community. The minimum basic requirement for water consumption per person is 121 liters per day. These needs are needed in the needs of drinking, cooking, washing clothes, bathing, cleaning the house and the needs of worship. According to Poedjastanto, Indonesia's minimum basic need is 70 liters / person / day (Pusat Komunikasi Publik Kementrian PUPR, 2007).

b) Non-Domestic Water Needs
Non-domestic water needs are water needs that include urban (social and public) facilities in the planning area. Urban facilities located in Ambarita include education, health, worship and recreation. The calculation of non-domestic water demand is as follows (Fatimah et al., 2014).

Total Non-Domestic Water Needs = ∑Water Requirement for Industry + Water Needs for Trade and Services + Water Needs for Other Economic Activities.
The water requirement of each activity is the multiplication of the number of units and the water requirement per unit of activity.

C. Domestic Wastewater Discharge
In calculating the volume of domestic wastewater, it is necessary to know the volume of clean water requirements. The need for clean water is expressed as the peak hour discharge which is the amount of water during the greatest use in 24 hours (Martono, 2015). The peak hour discharge is calculated by the formula below. Q jp = f jp x Qr Annotation: Qjp = peak hour discharge (m 3 /s) Qr = average discharge (m 3 /s) fjp = peak hour factor The peak hour discharge states the amount of clean water needed. Wastewater discharge states the amount of wastewater or waste produced by the community during a certain period of time. According to (Martono, 2015) wastewater discharge can be calculated in the following formulation below. = 80% × Annotation: Qab = wastewater discharge (m 3 /s) The minimum wastewater discharge (Qmin) is the discharge of wastewater when using minimum water. The minimum discharge calculation requires equivalent population data (PE) and average wastewater discharge (Qr ab). Equivalent population (PE) is the amount of organic waste decomposed from household and commercial activities (Martono, 2015).
Annotation: Qmin = minimum wastewater discharge (m 3 /s) PE = equivalent population (people) Qr ab = average wastewater discharge (m 3 /s) n = number of nodes in a wastewater distribution system The peak discharge calculation can be obtained from the equation below. Qpeak = Qr ab x fpeak Annotation: Qpeak = Peak discharge of wastewater (m 3 /s) Q r ab = Average water discharge waste (m 3 /s) Fpeak = Peak factor The maximum wastewater discharge (Qmax) is the discharge of wastewater at the time of maximum water use. The Qmax calculation uses the maximum daily factor value data which is the ratio between the average water (Martono, 2015).

D. Wastewater Channelling System
The design of the wastewater distribution system must first know the value of the initial full flow rate (initial Qfull). The initial full flow rate (initial Qfull) is calculated as follows (Martono, 2015).

Design of Main Sewers Graph
Source : (Martono, 2015) The calculation of the dimensions of the sewerage is carried out after the initial full flow rate (initial Qfull) and full flow velocity (vfull) are assumed. The channel diameter is generated by the following formula (Martono, 2015).
Once the diameter is obtained, the hydraulic radius (R) can be calculated. The hydraulic radius is calculated using the following equation (Martono, 2015). = 0.25 × Annotation: Dcount = diameter of the output channel calculation (mm) Q full Initial = initial full flow rate (m 3 /s) Vfull = full flow rate (assumed) (m/s) R = hydraulic radius (mm) D = channel diameter (mm) The slope of the pipe (slope) is one of the factors that greatly affects the value of V full . A minimum slope of the pipe is required so that the minimum flow speed is obtained by self-cleansing so that deposits do not occur in the sewerage. The pipe slope value can be an assumption provided that the value of Vfull is not less than 0.6 m/s and not more than 3 m/s (Martono, 2015). Calculate the slope of the field using the following equation (Pratiwi & Purwanti, 2015). Annotation: S = slope of pipe or channel (%) n = Manning's coefficient of roughness Vpeak = peak flow rate (m/s) R = hydraulic radius The full discharge of wastewater (Qfull) is the discharge of wastewater when the pipe is full. In addition, it is necessary to calculate the minimum water level (dmin) and minimum flow velocity (vmin). This was done so that the need for flushing could be identified in a waste water distribution system. =

A. Study Area Conditions
The Ambarita area is in position 2°40'92" east longitude and 98°49'47" South latitude. Slope conditions in the Ambarita area, which is included in the Simanindo Priority Area, have a slope of more than 40%, which is 24% of the total land area, which is difficult to build, while the easy-to-build areas that are on a slope of 0-8% are only around 18%. According to (Badan Pusat Statistik, 2018) The total population of the Ambarita area is 1043. The Ambarita area was selected as the study area because the Ambarita area is a priority tourist area whose population will increase rapidly due to tourism activities. This will affect the generation of domestic waste water, which, if not handled, will cause problems with Lake Toba water pollution. The problem of wastewater in the Ambarita area has yet to be addressed because there is no sewage system and WWTP.

B. Population Projections of the Ambarita Area
In the planning of this domestic wastewater distribution system, a planning area is determined which will be calculated based on the maximum capacity of the design that will be made in the Master Plan draft, namely the area that is the busiest center of tourism activities to residential housing. The population to be served is the population of progressive projections and the design period used in this planning is 20 years from 2020 to 2040 according to the planning in the Master Plan draft in  From Figure 4, for the areas served, the number of parcels from each segment is obtained multiplied by the number of families (family cards) where each parcel consists of 5 family members, which can be seen in Table 1.

Table 1. Ambarita Area Population Per Segment
Annotation: 1. Segment = Division of the area to be served is divided into several segments 2. Block = A segment divided into service blocks 3. L = pipe length (m) 4. L equivalent = length of straight pipe (m) 5. Cumulative L = Addition of the equivalent length before and after (m) 6. H1 = initial height (m) 7. H2 = the final height (m) 8. Block area = Area per block (ha)

C. Clean Water Needs and Wastewater Projection
Wastewater discharge is the need for clean water from the total domestic and nondomestic water needs that people use every day. Of this water requirement, about 80% will become domestic wastewater. The Ambarita area is included in the rural category so that the need for house connections is 95 l/person/day and non-domestic water needs such as health, education, recreation and sports facilities seen from the planning needs to be served in the Ambarita Area Master Plan draft and non-standard water needs. -Domestic PU Cipta Karya. Calculation of water needs for berish and wastewater can be seen in Table 2 and Table 3.

D. Calculation of Pipe Dimensions
Pipes made of concrete are chosen in the planning of domestic wastewater networks because the material is not easy to react and has a large size. Calculations for the dimensions of concrete pipes, which have a manning coefficient (n) of 0.012 -0.016. The results of the calculation of pipe dimensions can be seen in Table 4.

Table 4. Calculations to get pipe dimensions and values for Vfull
Annotation: 1. Qmd = Maximum discharge of wastewater in 1 day (m 3 /second) 2. Qinf = Infiltration discharge (m 3 /sec) 3. Qpeak = Peak discharge of wastewater (m 3 /sec) 4. Q design = Total infiltration discharge and peak discharge (m 3 /sec) 5. n Pipe = Manning coefficient (roughness of the pipe) 6. Vfull = Maximum speed (0.6-3 m 3 /s) 7. Qfull = Maximum discharge (m 3 /sec) 8. Qd/Qf = The ratio of the discharge of water needs per day to the maximum discharge 9. d/D = the ratio of the water level to the pipe diameter 10. Vp/Vfull = The ratio of the minimum speed to the maximum speed The planning of the piping network from the calculations that have been obtained is seen in Figure 5.

E. Sewerage with a Closed System
The distribution of domestic wastewater is carried out in a closed system, which aims to ensure that the distribution does not interfere with activities in the vicinity. The treated water or WWTP effluent will be flowed into the waters of Danu Toba, in accordance with the established quality standards, namely Peraturan Pemerintah Number 82 of 2001 class 2 (Presiden Republik Indonesia, 2001), which is designated for water recreation infrastructure / facilities, freshwater fish farming, animal husbandry, and irrigation.

F. Equipment and Types of Piping used
The equipment and types of piping that will be used for piping in the Ambarita area are manholes, clean out, and using concrete pipes.

G. Domestic Wastewater Treatment Plant Capacity
The quantity of wastewater to be treated at the wastewater treatment plant has been obtained from previous calculations, which is the amount of the average discharge of wastewater, the WWTP discharge is 0.06495 m 3 /s and the WWTP capacity is obtained as follows.
Daily WWTP capacity (m 3 /day) = ∑Qr of waste water = 0,06495 m3 s 86400 = 5611,460 3 The design that will be planned in determining the WWTP Layout in the Ambarita area can be seen in Table 5.

Table 5. Dimensions for Layout of Domestic Wastewater Treatment Plants
The following is the WWTP layout based on the planning design which can be seen in Figure 6.

H. Technology Recommendations for Domestic Wastewater Treatment Plants
The laboratory test results of the water quality of Lake Toba at Siallagan Harbor, which is located in Ambarita, can be seen at Table 6.  Indonesia, 2001) concerning Water Quality Management and Water Pollution Control are fecal coliform and free chlorine. According to the characteristics of domestic wastewater, fecal coliform is included in biological characteristics, whereas, free chlorine is classified as organic chemical characteristics which usually comes from the use of detergents from hotels, households, and other public facilities. Biological processing technology is selected in the removal of these two parameters because of its lower cost than chemical processing and limited land availability. The choice of biological technology is also a request from the Samosir Regency Environmental Service. Several alternative technologies that are assessed based on the advantages and disadvantages can be seen in Table 7.  Table 7. Wastewater Treatment Alternative Assessment Source : Said (2008) in Asmadi dan Suharno (2012) in (Nasoetion et al., 2017), 1 Hasil analisis Based on the total value of technology selection with several assessment criteria, the biofilter was selected as an alternative technology to be used in domestic wastewater treatment in the Ambarita area. The biofilter that will be used in domestic wastewater treatment in the Ambarita area is anaerobic-aerobic biofilter, because the use of anaerobic processes, organic pollutants in wastewater will be converted into carbon dioxide gas and methane which is broken down by anaerobic bacteria and facultative bacteria without using energy. like an air blower, but the content of ammonia and hydrogen sulfide gas (H2S) cannot be lost. So, if only anaerobic biofilter is used, only organic pollutants such as BOD, COD and TSS can be removed. Therefore, it is necessary to process an aerobic biofilter that can break down the remaining organic pollutants from the anaerobic process, where organic pollutants will be converted into CO2 and H2O (Kemenkes, 2011). An illustrative anaerobic-aerobic biofilter process can be seen in Figure 7.

Figure 7. Illustration of Anaerobic-Aerobic Biofilter Unit Model
Source : (Republik Indonesia, 2017) In the provision of two parameters that exceed the quality standard of Peraturan Pemerintah Number 82 of 2001 (Presiden Republik Indonesia, 2001), namely fecal coli and free chlorine, the efficiency of the aerobic-anaerobic biofilter according to (Hariyani & Sarto, 2018

CONCLUSIONS
The conclusions from the above discussion are as follows: 1. Quantity and quality of domestic wastewater in the Ambarita area: a. The total discharge of wastewater in the planning area is = 0.06495 m 3 /sec b. The quality of the waters of Lake Toba which indicates pollution from domestic wastewater is COD 12.97 mg/l, TSS 3.5 mg/l, BOD <2 mg/l, fecal coli 150 coliform/100ml, Free Chlorine 0.32 mg/l, and total phosphate as P 0.0228 mg/l. The only parameters that exceed the quality standard are free chlorine and fecal coli. 2. The planned waste water distribution system is an Ambarita service area distribution system in the MasterPlan draft that focuses on congested activities. The pipe used is a concrete pipe because is strong enough for the distribution of domestic wastewater. The diameter used for pipes made of concrete is 100 mm, 125 mm, 150 mm, 200 mm, and 250 mm and it will have 5 manholes.
3. The total length of pipe required for each diameter of the commonly pipe used in the market, 100 mm = 1010 m; 125 mm = 663 m; 150 mm = 248 m; 200 mm = 338 m and for 250 mm = 285 m.
4. Wastewater treatment plants selected to use anaerobic-aerobic biofilter with effectiveness in reducing fecal coli and free chlorine by 99.9% and 65%. Although, the free chlorine allowance has not met the quality standards of Peraturan Pemerintah Number 82 Year 2001 class 2 (Presiden Republik Indonesia, 2001), the use of this anaerobic-aerobic biofilter is the most effective alternative technology.
5. Reduction of the key parameters of domestic wastewater, namely BOD, COD and TSS with allowances of 85%, 85% and 80% in using anaerobic-aerobic biofilter technology.