Developing a Decentralized and Integrated Water Management System for Neighborhood Communities Within Indonesia’s Informal Urban Settlements

Abstract

Decentralized water management systems can be a viable solution to the sanitation problems of informal urban areas. To be successful, they have to be tailored to the specific context of an area by using its social and cultural potentials instead of thinking in solely technical system measures. This is shown for the example of Kampung Tamansari, an informal settlement located at a riverbank in Bandung. An analysis of the existing water sources reveals that the current handling of water has a destructive impact on human health and environment. Field research in Tamansari suggests that the neighborhood communities, their leaders, and religious institutions are promising catalysts for the implementation of a new system. A high level of self-organization, social cohesion, democratic mechanisms, and educational infrastructure are to be mentioned. Based on those findings, an integrated water system for one neighborhood is proposed. The implementation, management, and water-related education are realized through the use of the identified community potentials. Technical components such as septic tanks, constructed wetlands, and water storages are designed to facilitate public spaces. Benefits for involved stakeholders ensure the system’s stability and increase the chances for a gradual expansion along the many rivers of Bandung and the countries metropoles.

Appendix

1.1 Household Usage and Water Sources

Source	Use	Amount [L/Person/Day]	Amount (%)
Purified rainwater	Drinking	2	2.2
Purified rainwater	Cooking	3	3.3
Purified rainwater	Praying	1.1	1.3
Purified rainwater	Basic hygiene	5	5.6
Constructed wetland	Shower	45	50.1
Constructed wetland	Dishes	6	6.7
Constructed wetland	Clothes	5.7	6.3
Constructed wetland	Household	0.8	0.9
Re-used grey water	Toilet	21.2	23.6
Total		89.8

1.2 Calculation: Rainwater Catchment Area

Description	Result
Need [l/pers/day]	11.1
Total need [l/pers/year]	4048.3
Precipit. [mm/year]	2164
Area/Person [m2]	2.2
Total Area [m2]	1103.7
Loss compensation [%]	18
Savings from bottled water [Rp/Pers/Month}	61500
Average income [%]	3.3

1.3 Calculation: Rainwater Storage

Month	Precipitation [mm]	Collected [m3]	Efficiency factor	Consumed [m3]	End of month inventory [m3]
November	272	300.2	0.85	168.7	86.5
December	291	321.2	0.85	168.7	190.8
January	243	268.2	0.85	168.7	250.1
February	217	239.5	0.85	168.7	285.0
March	257	283.7	0.85	168.7	357.4
April	246	271.5	0.85	168.7	419.5
May	166	183.2	0.85	168.7	406.5
June	77	85.0	0.85	168.7	310.1
July	70	77.3	0.85	168.7	207.0
August	68	75.1	0.85	168.7	102.1
September	83	91.6	0.85	168.7	11.3
October	174	192.1	0.85	168.7	5.9
Total	2164	2196.4		1855.7
Max. Storage Inventory [m3] = Storage Size	419.5

1.4 Calculation: Volume Septic Tank

Based on “Low Cost Urban Sanitation” (Mara 1996, 74)

Term	Description	Formula	Result
	Blackwater [l/person/day]		38.7
	Blackwater total [m3/day]	19.35
VSC	Zone 1: scum storage	0.4 * Vsl	12
Vn	Zone 2: sedimentation	10−3P * q * tn	2.944148
Vd	Zone 3: sludge digestion	0.5 * 10−3P * td	3.798542
Vsl	Zone 4: digested sludge storage	r * P * n	30
th	Hydraulic retention time [years]	1.5–0.3 log(Pq)	0.304305
P	Population [n]		250
q	Wastewater flow [l/day]		38.7
td	Anaerobic digestion time	1853 * T−1.25	30.38834
T	Bandung av. temperature		26.8
r	Rate of sludge digestion [m3/person/year]	0.04
n	Desludging interval [years]		3
V	Septic tank volume [m3]		48.74269

1.5 Calculation: Constructed Wetlands Area

Based on “Constructed Wetlands Manual” (UN-Habitat 2008, 18)

Term	Description	Formula	Result
Bodc	Bod concentration before treatment [mg/l]	250
Bodc	Bod contribution [mg/pers/day]	40
Qd	Daily flow rate [m3/day]	p * q	34.2956
Ci	Influent BOD5 concentration[mg/l]	408.2
Ce	Effluent BOD5 concentration[mg/l]	30
KBOD	Rate constant [m/d]	Kt * d * n	0.2
Kt		K20 (1.06)(T−20)
K20	Rate constant at 20 °C	20 °C (d−1)
d	Depth of water column [m]
n	Porosity of substrate [percentage expressed as fraction]	0.3
	Substrate depth [cm]		70
P	Population		500
q	Flow rate [l/person/day]		68.6
Ah	Surface area of bed [m2]	(Qd(Ci-Ce))/KBOD	490
Ap	Surface area [m2]/person	Ah/p	0.98

1.6 Calculation: Water Storage

Description	m3
CW output total [m3]	34.3
Max daily need [m3]	28.75
Safety factor	1.5
Water storage	51.4434