INTRODUCTION

Adequacy of the treatment capacity in

water and wastewater services

Ana Rita Ramos, Francisco Mira

Entidade Reguladora dos Serviços de Águas e Resíduos (the Water and Waste Services Regulation Authority), Portugal,

www.ersar.pt; geral@ersar.pt

Phone: +351 210 052 200; Fax: +351 210 052 259

The adequate utilization of the treatment plants capacity for water supply and/or wastewater is reflected on the sustainability of the infrastructure management operators and, hence, on the sustainability of

the service management they provide.

The treatment plants size is based on factors such as the population to be served and the capitation, and, consequently, on the volume of water to be treated, the quality of the water source (in the case of

water supply systems) and the quality of the receiving environment (in the case of a wastewater systems), among other factors. Therefore, the reliability of the size estimates when designing treatment

facilities is particularly relevant so as to make sure that the installed treatment capacity is used under appropriate conditions.

However, the use of the installed capacity in inadequate conditions may be related with factors other than those mentioned above. Once the treatment infrastructure is built, the connection levels to the

service is one of the factors that may influence, the utilization of the treatment capacity installed.

This poster aims to quantify the current percentage of the total water volume which is treated properly taking into account the treatment infrastructure capacity and to analyze the influence of the connection

levels to water services on the adequate utilization of the capacity installed at the water treatment plants.

The quantification of the volume of water and wastewater treated adequacy to the installed

capacity in treatment plants, as well as how this relates to the connection levels to water and

wastewater services, is achieved by using the data collected under the quality of service

assessment data provided by the operators in 2012.

Table 1: describes the quality of service indicators and data provided by the operators and used

in this study.

The universe considered encompasses the water and wastewater treatment multimunicipal

operators, both retail and bulk services, covering about 93% of the Portuguese population.

We considered only the water treatment plants (WTP) and wastewater treatment plants (WWTP)

for which the «Adequacy of treatment capacity» indicator was answered by the operators, which

represent 39% of total WTP (101) and 12% of total WWTP (905).

But, to analyze the treatment plants usage behavior given a real increase in the number of

connections to the water supply and wastewater service, we considered only treatment plants

that showed, in 2012, an inadequate treatment capacity against the water flow treated. The table

below characterizes the sample used for this study

Table 2: characterizes the sample used for this study

In order to assess if the number of end users that are connected to water and wastewater

services affected the utilization of the treatment capacity, we analyzed two distinct scenarios:

The study considers the following intervals to evaluate the performance of the adequacy of

treatment capacity:

METHODS RESULTS

According to the results, and as it shows in the figure below, only few WTP and WWTP reached the

suitable treatment capacity after applying scenario 1 and 2

CONCLUSIONS

inspiring change

Figure 1 – Behaviour of WTP when we apply scenario 1 and scenario 2

Regarding the water treatment plants usage behaviour when we use the scenario 1

and when we use the scenario 2, the figure shows the following:

ERSAR (2013), Relatório anual do setor de águas e resíduos em Portugal, Entidade Reguladora dos Serviços de Águas e Resíduos, 2011.

ERSAR/LNEC (2012), Guia de avaliação da qualidade dos serviços de águas e resíduos prestados aos utilizadores, 2.ª geração do sistema de indicadores.

ERSAR/LNEC (2009), Guia de avaliação da qualidade dos serviços de águas e resíduos prestados aos utilizadores, 1.ª geração do sistema de indicadores.

www.iwahq.org

Total of maximum monthly installed

capacity of treatment

(1000 m3/month)

Total of maximum monthly volume

treated

(1000 m3/month)

WTP 41.506 21.207

WWTP 4.585 1.963

Regarding the wastewater treatment plants usage behaviour, the figure shows the following:

Percentage of total households located in the operator’s intervention area for which the infrastructure of the service water distribution and /or collection and drainage are available.

Physical

accessibility of the

service (%)

Percentage of total households located in the operator’s intervention area for which the infrastructure of the service water distribution and/or collection and drainage are available and has effective service.

Connection to

service (%)

Maximum percentage of used capacity in the existing treatment plants.

Treatment

utilization (%)

Maximum monthly volume of water treated during the year.

Maximum monthly

volume of water

treated (m3/month)

Maximum volume of water treated that the system is capable to produce during the year.

Maximum monthly

treatment capacity

(m3/month)

Figure 2 – Behaviour of WWTP when we apply scenario 1 and scenario 2

Figure 3 – Adequacy of the treatment capacity in water and wastewater services after applying scenario 1 and 2

For those few infrastructures that reached the satisfactory performance we have to create

incentives aimed at promoting connections and adherence to public water distribution networks.

Most infrastructure has kept its unsatisfactory performance shown an oversizing as a result of

wrong assumptions (population served) at the time of its construction.

For these infrastructures, solutions may pass by:

a) Create incentives aimed at promoting connections and adherence to public water distribution

networks and wastewater collection;

b) For WWTP, integrated or complementary treatment solutions, industrial, agro-industrial and

agricultural effluents, under additional or ancillary activities;

c) Analyze the existing legal framework and possible revisions in order to optimizing

infrastructure taking into account the proximity to potential users and less on issues related to

the administrative division of the managing bodies.

Good

performance

Satisfactory

performance

Unsatisfactory

performance

WTP 90-100% 70-90% 0-70%

WWTP 80-100% 60-80% 0-60%