This paper presents the evaluation of the proportion of the population connected to safely managed wastewater collection systems (PW) based on the proportion of population connected to wastewater collection systems and additional specific indicators that can properly inform on the extent of environmental risks associated with the disposal of wastewater. A safely managed wastewater factor (SF) is proposed to take into consideration the environmental risks when evaluating PW. At the practical level, results of evaluation of the proposed PW and SF indicators in Lebanon are then presented and discussed. Finally, the conclusion and further developments are presented.

INTRODUCTION

The 2030 Agenda for Sustainable Development was adopted at the United Nations Sustainable Development Summit in September 2015 and includes 17 sustainable development goals (SDGs) whose progress is monitored and reported upon through 169 targets (UN 2015). Goal 6 (SDG-6) on ‘ensuring availability & sustainable management of water & sanitation for all’ includes eight targets, the second one of which (target 6.2) is used for monitoring equitable access to adequate sanitation. The indicators, data sources, and the monitoring and reporting mechanism of SDG-6 targets are still under consideration and discussion by the concerned United Nations agencies.

The indicator ‘Percentage of population using safely managed sanitation services' is proposed globally to monitor the SDG target related to sanitation (UNSTATS 2015). According to WHO & UNICEF (2015), the safely managed sanitation services is defined by: a) the use of improved sanitation facility (i.e., flush or pour flush toilets to sewer systems, septic tanks or pit latrines, ventilated improved pit latrines, pit latrines with a slab, and composting toilets); b) the use of sanitation facility which is not shared; and c) the use of sanitation facility where excreta are safely disposed in situ or transported and treated off-site. This indicator can be evaluated by combining data on the proportion of the population using different types of improved sanitation facilities with estimates of the proportion of wastewater or fecal waste which are safely disposed (WHO & UNICEF 2015). For the purpose of systemizing the evaluation of the proportion of wastewater or fecal waste which are safely disposed or treated, the sanitation facilities could be divided into two main categories:

  • (a) Sewerage systems: in this category the evaluation of the proportion of wastewater which is safely treated and reused could be performed based on country data from service providers or regulators who usually possess authentic technical and operational data related to the annual volumes of produced, treated, and reused wastewater.

  • (b) On-site sanitation systems: in this category the evaluation of the proportion of fecal waste which is safely treated and disposed necessitates combination of different data sources (service providers or regulators, household surveys, censuses and simulation methods based on types of toilets people use and the country they are used in). In Lebanon, such systems are owned and managed at the household level, therefore, it is difficult to obtain for this category accurate data related to the annual volumes of the disposed fecal waste. Data related to the on-site sanitation systems are generally obtained from household surveys and census.

Many research studies have sought to develop indicators and methods to measure the wastewater or fecal waste which is safely treated, reused, or disposed (Eawag/Sandec 2008; Scott 2011; Peal et al. 2014; WHO & UNICEF 2015). The fecal waste flow diagram method in particular was found to be an important tool for explaining the situation and challenges and for drawing attention to the need for improved fecal sludge management. Examples of using this method are provided in Scott (2011) and Peal et al. (2014). However, the above-mentioned studies did not address the assessment of accurate safety factors calculated based on the proportion of pollutants released to the environment.

This study aims to propose a framework for quantifying the proportion of population connected to safely managed wastewater collection systems based on the proportion of population connected to wastewater collection systems and a safely managed wastewater factor (SF) that can properly inform on the extent of environmental risks associated with the disposal of the collected wastewater. The proposed approach is then applied to the wastewater collection systems in Lebanon.

EVALUATION OF THE PROPORTION OF POPULATION CONNECTED TO SAFELY MANAGED WASTEWATER COLLECTION SYSTEMS

Hereafter, a safety factor calculated based on the proportion of pollutants released to the environment is proposed. The percentage of population connected to safely managed wastewater collection systems can be calculated by applying the safety factor ratings to the proportion of population connected to sewerage networks.

If P denotes the proportion of population connected to the wastewater network, which is calculated as follows: 
formula
1
where CP = number of population connected to wastewater network and TP = total number of population.
If we denote by PW the proportion of population connected to safely managed wastewater collection systems, PW could be then calculated using the following equation: 
formula
2
where SF (%) is a safety factor related to the safely managed wastewater collection services in a specific country.

The proposed safely managed wastewater factor will be limited to the sewerage systems only; the on-site sanitation systems are not considered in this study. The proposed methodological issues will be addressed in sequence.

Indicators related to safely managed wastewater

An effort has been pursued at the Arab regional level with the launching of a regional initiative for establishing a regional mechanism for improved monitoring and reporting on access to water supply and sanitation services in the Arab region (MDG + Initiative). This is an outcome of a series of resolutions adopted by the Arab Ministerial Water Council through a set of indicators that respond to regional concerns for monitoring and reporting on access to water supply and sanitation services in the Arab region (UN-ESCWA 2013). The initiative is based on a set of regional specific indicators that take into consideration the challenges associated with accessing these basic services in Arab countries (UN-ESCWA 2013).

These additional regional specific sanitation indicators include:

  • proportion of population connected to wastewater network;

  • proportion of primary, secondary, or tertiary treated wastewater;

  • proportion of safe reuse of secondary and/or tertiary treated wastewater.

The proportion of wastewater that had undergone primary, secondary, or tertiary treatment indicator has been widely used by different universal environmental organizations (US EPA 2009; Van Den Berg & Danilenko 2011; European Environment Agency 2013; UN-ESCWA 2013). The wastewater treatment reveals the extent of environmental risks associated with the disposal of treated or untreated effluent. Moreover, the safe reuse of treated wastewater can also reduce environmental risks by reducing wastewater discharge into the natural environment (Council of the European Communities 1986, 1991; Chowdhury & Al-Zahrani 2013), and they can also increase agricultural production in regions where water resources are extremely limited such as the Arab region (Karnib 2014).

Aside from the fact that the above-mentioned indicators were regionally proposed and agreed upon, they fully reflect the concerns about the safe management of the wastewater collection systems. Therefore, we will consider these indicators to evaluate the safely managed wastewater collection services.

It is important to mention that each country is peculiar to its social, institutional, and economic situations that influence its wastewater management policies and strategies. The identification of indicators is guided by the level of development of the sewerage systems in the country and the availability of data related to these systems. Therefore, the identified indicators could be addressed in different ways according to the specific situations of each country. At present, tertiary wastewater treatment in Lebanon is not applicable.

Table 1 provides descriptions of the considered indicators.

Table 1

Descriptions of the selected indicators

Indicator Descriptions and measurable variables 
Population connected to wastewater network (CPNumber of population connected to wastewater network (millions of population) 
Total population (TPTotal number of population (millions of population) 
Collected wastewater (CAnnual volume of collected domestic wastewater (MCM/year) 
Primary treated wastewater (W1Annual volume of collected domestic wastewater which has undergone primary treatment (MCM/year) 
Secondary treated wastewater (W2Annual volume of collected domestic wastewater which has undergone secondary treatment (MCM/year) 
Tertiary treated wastewater (W3Annual volume of collected domestic wastewater which has undergone tertiary treatment (MCM/year) 
Reuse of secondary treated wastewater (W4Annual volume of reused secondary treated domestic wastewater (MCM/year) 
Reuse of tertiary treated wastewater (W5Annual volume of reused tertiary treated domestic wastewater (MCM/year) 
Indicator Descriptions and measurable variables 
Population connected to wastewater network (CPNumber of population connected to wastewater network (millions of population) 
Total population (TPTotal number of population (millions of population) 
Collected wastewater (CAnnual volume of collected domestic wastewater (MCM/year) 
Primary treated wastewater (W1Annual volume of collected domestic wastewater which has undergone primary treatment (MCM/year) 
Secondary treated wastewater (W2Annual volume of collected domestic wastewater which has undergone secondary treatment (MCM/year) 
Tertiary treated wastewater (W3Annual volume of collected domestic wastewater which has undergone tertiary treatment (MCM/year) 
Reuse of secondary treated wastewater (W4Annual volume of reused secondary treated domestic wastewater (MCM/year) 
Reuse of tertiary treated wastewater (W5Annual volume of reused tertiary treated domestic wastewater (MCM/year) 

MCM, million cubic meters.

Evaluation of SF factor

Based on the types of collected wastewater treatment and reuse, safety factor could be evaluated for a specific sewerage systems at the regional or national level in the country, therefore, a sewerage system could be shown as having x% of pollutants released to the environment. In fact, the collected wastewater and associated pollutants are discharged directly into the environment in one, two, or three stages: a) directly without treatment, b) through a treatment plant, or c) through reuse after treatment; which leads to a distinction between raw and final pollutants. ‘Raw pollutants' are the pollutants assessed at the point where the wastewater leaves the dwelling (the case of domestic wastewater). ‘Final pollutants' correspond to the pollutants released to the environment. When wastewater is discharged directly to the environment, raw and final pollutants coincide. However, in practice, a domestic wastewater collection system may discharge part of its wastewater directly to the environment, thus releasing the pollutants directly, and thereafter supply the rest to a wastewater treatment plant. The treated wastewater could be discharged into the environment or reused. Since treated wastewater may still contain traces of the pollutants generated by the domestic use of water, the final pollutants of the water use unit would correspond to the sum of the directly released pollutants into the environment and that indirectly released through wastewater treatment plants before or after reuse.

The proposed approach is based on computing the final pollutants as a proportion of raw pollutants released to the environment based on type of treatment and/or reuse.

Domestic wastewater treatment effluent standards are commonly expressed as a minimum level of effluent quality in terms of biochemical oxygen demand measurements over a 5-day interval (BOD5) (US EPA 2009). In primary wastewater treatment, solids are removed from raw sewage through processes involving sedimentation. This process typically removes about 20% to 35% of solids and related organic matter (US EPA 2009). Secondary wastewater treatment includes an additional biological process in which organic materials are removed through bacterial synthesis. About 85% of organic matter in sewage is removed through this process (US EPA 2009). Tertiary treatment is capable of producing high-quality water before it is released to the receiving environment.

Table 2 provides typical raw and percentage removal of domestic wastewater pollutants expressed in BOD5 constituent in ton/MCM (Metcalf & Eddy 2003).

Table 2

Typical domestic wastewater BOD5 constituent in ton/MCM

  Raw conc.* (RPrimary treated effluent conc. (E1Secondary treated effluent conc. (E2Tertiary treated effluent conc. (E3Reused wastewater secondary treated conc. (E4Reused wastewater tertiary treated conc. (E5
Concentration 185 148 13 3.7 3.7 
% Removal – 20 93 98 98 100 
  Raw conc.* (RPrimary treated effluent conc. (E1Secondary treated effluent conc. (E2Tertiary treated effluent conc. (E3Reused wastewater secondary treated conc. (E4Reused wastewater tertiary treated conc. (E5
Concentration 185 148 13 3.7 3.7 
% Removal – 20 93 98 98 100 

* conc., concentration.

Source: Based on Metcalf & Eddy (2003).

It is important to mention that, because there is no ‘typical’ wastewater, the typical domestic wastewater BOD5 constituent in raw as well as primary, secondary, and tertiary effluent with or without reuse presented in Table 2 should only be used as a guide. Several types of constituent pollutant variations can occur depending upon the particular setting of the wastewater collection system.

If we denote by:

  • RP: total raw pollutants (in tons) contained in the total collected wastewater

  • FP: total final pollutants (in tons) released to the environment after treatment and reuse.

The SF factor is calculated as follows: 
formula
3
The raw and final pollutants are calculated as follows: 
formula
4
 
formula
5
Note: C, W1, W2, and W3 are the annual volume of collected, primary, secondary, and tertiary treated domestic wastewater, respectively, in MCM/year; W4 and W5 are the annual volume of reuse of secondary and tertiary domestic wastewater, respectively, in MCM/year; R, E1, E2, and E3 are the BOD5 constituent in ton/MCM for raw, primary, secondary, and tertiary treated effluent, respectively; E4 and E5 are the BOD5 constituent in ton/MCM for secondary and tertiary treated and reused effluent, respectively.
  • If FP = 0 then SF = 100% (no final pollutants released to the environment).

  • If FP = RP then SF = 0 (wastewater is discharged directly to the environment, therefore, raw and final pollutants coincide).

  • If 0 < FP < RP then SF scores vary between 0 and 100%.

The higher the ratings of the SF, the less the pollutants from raw wastewater reach the environment.

APPLICATIONS AND ANALYSIS OF RESULTS

In order to examine the various steps of the proposed approach and to put the developed framework on a practical level, this section describes an application of the developed methodology to assess the evaluation of the proportion of population connected to safely managed wastewater collection systems in Lebanon.

Background information

The climate of Lebanon is characterized by heavy rain in the winter season from January to May and dry and arid conditions in the remaining seven months of the year. The renewable water resources per capita amount to 839 m3/capita/year with an expected decrease in the coming years. High population growth and the effect of climate change on water availability are the main challenges facing water demand in the country, with expected higher temperatures, changing rainfall patterns, and increased frequency of extreme weather events. At present, the population of Lebanon is calculated at about 4.65 million and produces about 252 million cubic meters of domestic wastewater annually. 58.54% of the population are connected to sewerage systems and 41.46% are using on-site sanitation systems which are mainly flush toilets to septic tanks or pit latrines.

The responsibilities of water supply and wastewater collecting and treatment systems in Lebanon are delegated to the following four regional water authorities (RWAs): Beirut and Mount Lebanon (BML), North Lebanon, South Lebanon, and Bekaa. Table 3 presents the population served by RWAs and the data of the measurable variables and indicators necessary to evaluate the proposed safety factor for the year 2015. These data are obtained from the available records at the RWAs, the Ministry of Energy and Water (MEW) in Lebanon (MEW 2012), and data compiled by the author.

Table 3

Data of the measurable variables and indicators

Water authority CP TP C W1 W2 W3 W4 W5 
BML 1.77 2.49 93.35 45.00 0.00 0.00 0.00 0.00 
North Lebanon 0.42 0.89 26.25 0.00 6.92 0.00 0.00 0.00 
South Lebanon 0.33 0.71 18.43 6.52 3.20 0.00 0.00 0.00 
Bekaa 0.20 0.57 9.35 0.00 0.90 0.00 0.45 0.00 
Water authority CP TP C W1 W2 W3 W4 W5 
BML 1.77 2.49 93.35 45.00 0.00 0.00 0.00 0.00 
North Lebanon 0.42 0.89 26.25 0.00 6.92 0.00 0.00 0.00 
South Lebanon 0.33 0.71 18.43 6.52 3.20 0.00 0.00 0.00 
Bekaa 0.20 0.57 9.35 0.00 0.90 0.00 0.45 0.00 

Source: Compiled by the author from the available records at the RWAs, the Ministry of Energy and Water (MEW) in Lebanon (MEW 2012).

Note: CP and TP are population connected to wastewater network and the total population, respectively, in millions of population; C, W1, W2, and W3 are the annual volume of collected, primary, secondary, and tertiary treated domestic wastewater, respectively, in MCM/year; W4 and W5 are the annual volume of reuse of secondary and tertiary domestic wastewater, respectively, in MCM/year.

Analysis of results

First, the values of the considered performance indicators P, PW, SF, RP, and FP are calculated using Equations (1)–(5), respectively. Table 4 presents the resulting values.

Table 4

Resulting values of RP, FP, SF, P, and PW for year 2015

Water authority RP (tons) FP (tons) SF (%) P (%) PW (%) 
BML 17,270.49 15,605.49 9.64 71.23 6.87 
North Lebanon 4,855.70 3,665.46 24.51 47.53 11.65 
South Lebanon 3,409.37 2,617.65 23.22 46.48 10.79 
Bekaa 1,730.49 1,571.51 9.19 35.39 3.25 
Water authority RP (tons) FP (tons) SF (%) P (%) PW (%) 
BML 17,270.49 15,605.49 9.64 71.23 6.87 
North Lebanon 4,855.70 3,665.46 24.51 47.53 11.65 
South Lebanon 3,409.37 2,617.65 23.22 46.48 10.79 
Bekaa 1,730.49 1,571.51 9.19 35.39 3.25 

Note: RP and FP are total raw and final pollutants, respectively; SF is safely managed wastewater factor; P is the proportion of population connected to piped wastewater network, and PW is the proportion of population using safely managed wastewater collection systems.

Figure 1 presents the proposed safely managed wastewater collection services ratings along with the proportion of population connected to wastewater network indicator and the proportion of population connected to safely managed wastewater collection systems indicator in the four RWAs.
Figure 1

The proposed PW indicator along with P and SF indicators in the four RWAs.

Figure 1

The proposed PW indicator along with P and SF indicators in the four RWAs.

The proportion of population connected to piped wastewater network is 47.53% in the North Lebanon water authority and 24.51% of the collected raw wastewater pollutants are removed. As a result, the proportion of population connected to safely managed wastewater collection systems measures only 11.65%. This means that only 11.65% of the population are connected to sewerage systems with collected wastewater being disposed without any pollutants released to the environment (almost all raw wastewater pollutants are removed before discharge to the environment).

Similarly, despite the high rate of the population connected to a piped wastewater network in the BML water authority, the proportion of population connected to safely managed wastewater collection systems is 6.87% only.

The above-mentioned results confirm the necessity to put the management policies and strategies of the wastewater collection systems in Lebanon on a sustainable footing. This can be done by developing wastewater treatment and reuse related infrastructure to reduce the proportion of pollutants released to the receiving environment coupled with development of wastewater reuse projects.

With the purpose to compare the SF score calculated at the national level in Lebanon, which amounts to 13.96%, and when using an approximate similar safety factor for sewerage systems proposed by WHO & UNICEF (2015), which is set to 60% for upper middle income countries, the calculated safety factor based on the percentage of pollutant removal proposed in this paper is much lower than the approximate common value mentioned above. However, 92% of the collected wastewater in Lebanon is disposed without treatment, therefore, the 60% safety factor is not appropriate for the Lebanese case. These results confirm that information about the actual pollutants released to the environment are not properly accounted for by using approximate safety factors estimated based on a common classification of countries, which may lead to a bias in the overall assessment of the proportion of population connected to safely managed wastewater collection systems.

CONCLUSION AND FURTHER DEVELOPMENT

This study proposes a framework for quantifying the proportion of population connected to safely managed wastewater collection systems indicator. In addition to the universal sanitation indicator (proportion of population connected to wastewater network), a safety factor that reflects the safely managed wastewater collection services is considered. The evaluation of the proposed safety factor is based on computing the final pollutants as a proportion of the raw pollutants released to the environment based on type of treatment and/or reuse. The proposed approach is then applied to the wastewater collection systems in Lebanon.

The established safely managed wastewater factor aims to improve monitoring and reporting on access to safely managed sanitation services in the Arab region. It could be of use to evaluate the proposed SDG indicators ‘percentage of population using safely managed sanitation services' and ‘percentage of wastewater safely treated’ under the SDG targets 6.2 and 6.3, respectively.

In this initial stage, the considered safely managed wastewater indicators focus on access to sewerage systems. The extension of this approach is to consider fecal waste management safety factors for different types of on-site sanitation facilities. These safety factors could be calculated based on the overall pollutants released to the environment during the different phases of the on-site sanitation service chain (direct discharge, emptying, transportation, treatment, and disposal or reuse) where annual volumes of produced fecal waste and amounts of typical raw and removal of waste pollutant constituents should be estimated. This aspect, to promote access to sustainable safely managed sanitation services in developing countries, is still under development at our university.

REFERENCES

REFERENCES
Chowdhury
S.
Al-Zahrani
M.
2013
Fuzzy synthetic evaluation of treated wastewater reuse for agriculture
.
Environment, Development and Sustainability
16
,
521
538
.
Council of the European Communities
1986
Council Directive on the Protection of the Environment, and in Particular of the Soil, When Sewage Sludge is used in Agriculture
.
Official Journal of the European Communities (86/278/EEC)
.
Council of the European Communities
1991
Urban Waste Water Directive
.
Official Journal of the European Communities (91/271/EEC)
.
Eawag/Sandec (Department of Water, Sanitation in Developing Countries, Swiss Federal institute of Aquatic Science and Technology)
2008
Fecal Sludge Management. Sandec Training Tool 1.0 - Module 5
,
Switzerland
.
European Environment Agency
2013
Urban waste water treatment (CSI 024) – Assessment published Jan 2013. Available at: http://www.eea.europa.eu/data-and-maps/indicators/urban-waste-water-treatment/urban-waste-water-treatment-assessment-3
(accessed 5 January 2016)
.
Karnib
A.
2014
A methodological approach for quantitative assessment of the effective wastewater management: Lebanon as case study
.
Environmental Processes Journal
1
(
4
),
483
495
.
DOI 10.1007/s40710-014-0032-8.
Metcalf and Eddy, Inc
.
2003
Wastewater Engineering Treatment and Reuse
.
McGraw-Hill
,
New York
,
USA
.
MEW
2012
National Strategy for the Wastewater Sector
,
Ministry of Energy and Water
,
Resolution No. 35, Date 17/10/2012
,
Beirut, Lebanon
.
Peal
A.
Evans
B.
Blackett
I.
Hawkins
P.
Heymans
C.
2014
Fecal sludge management: analytical tools for assessing FSM in cities
.
Journal of Water Sanitation and Hygiene for Development
4
(
3
),
371
383
.
Scott
P.
2011
Unbundling Tenure Issues for urban Sanitation Development
.
PhD thesis
,
Loughborough University of Technology
,
UK
.
UN-ESCWA
2013
Water Development Report 5 – Issues in Sustainable Water Resources Management and Water Services
.
UN-ESCWA
,
Beirut, Lebanon
,
E/ESCWA/SDPD/2013/4
.
United Nations (UN)
2015
Transforming Our World: the 2030 Agenda for Sustainable Development (Draft outcome document of the United Nations Summit for the Adoption of the post-2015 Development Agenda). Available at: http://www.un.org/pga/wp-content/uploads/sites/3/2015/08/120815_outcome-document-of-Summit-for-adoption-of-the-post-2015-development-agenda.pdf
(accessed 6 January 2016)
.
United Nations Statistics Division (UNSTATS)
2015
Second meeting of the IAEG-SDGs (26–28 October 2015 Bangkok), Available at: http://unstats.un.org/sdgs/meetings/iaeg-sdgs-meeting-02
(accessed 1 December 2015)
.
U.S. Environmental Protection Agency (US EPA)
2009
State of the Great Lakes
.
EPA 950 K 09 001
,
Washington DC
,
USA
.
Van Den Berg
C.
Danilenko
A.
2011
The IBNET Water Supply and Sanitation Performance Blue Book
.
The International Benchmarking Network for Water and Sanitation Utilities Data book, Water and Sanitation Program, World Bank
,
Washington DC
,
USA
.
WHO and UNICEF
2015
Methodological note: Proposed indicator framework for monitoring SDG targets on drinking-water, sanitation, hygiene and wastewater. Available at: http://www.wssinfo.org/fileadmin/user_upload/resources/Statistical-note-on-SDG-targets-for-WASH-and-wastewater_WHO-UNICEF_21September2015_Final.pdf
(accessed 14 January 2016)
.