Poster - Emergency control discharges in sewerage services

PERFORMANCE INDICATOR DEFINITION

ERSAR INTERVENTION

The PI used has been defined as:

Based on the experience in applying the UPM methodology to evaluate the indicator,

ERSAR adopted a metric based on the frequency of discharges depending on the uses of

the receiving waters:

The ERSAR’s evaluation of quality of service in this issue of discharges is represented in

the next scheme, where are mentioned the performance indicators (PI) for each type of

discharges (AR12, AR13, AR14 and AR15).

To control de emergency discharges (AR13) ERSAR chose, as an initial approach, to

evaluate only discharges occurring upstream of the WWTP and PS.

For the 284 operators in Portugal it is estimated that there are about 5 567 dischargers in

PS and WWTP.

INTRODUCTION

Rute Rodrigues, Maria José Franco, Paula Freixial

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

www.ersar.pt; [email protected]

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

Intermittent wet weather discharges from urban wastewater systems represents a potentially significant source of release of pollutants to the aquatic environment

One of the aims of the Portuguese water and waste services regulation authority (ERSAR) is the evaluation of the quality of service provided by the operators to the end-users. The evaluation of the

quality of service includes three goals:

• protection of user interests,

• operator sustainability and

• environmental sustainability.

In the environmental sustainability , the pollution prevention of receiving waters has been monitored by evaluating the extent to which the wastewater discharge parameters of treated wastewater is met

in the wastewater treatment plants (WWTP) and by evaluating the adequate disposal of the sludge produced at WWTP. Therefore, a gap remained in the integrated water urban cycle philosophy

concerning the discharges of raw wastewater and storm water through overflows in the network or by-pass of pumping stations (PS) or WWTP.

The potential pollution caused by intermittent wet weather discharges is a concern for ERSAR and recently an indicator to assess the problem has been implemented.

PROBLEM

CONCLUSIONS

inspiring change

References: ERSAR/LNEC (2012), Guia de avaliação da qualidade dos serviços de águas e resíduos prestados aos utilizadores, 2ª geração do sistema de indicadores. Portugal. http://www..ersar.pt

ERSAR (2013), RASARP 2012, Relatório anual dos serviços de águas e resíduos em Portugal, Portugal. http://www.ersar.pt.

EPA (1999),Combined Sewer Overflows – Guidance for monitoring and modeling, United States of America

www.iwahq.org

Emergency control discharges in

sewerage services

RESULTS

Uses of he receiving water Allowed frequency of discharges

areas wirh bathing and water contact sport <=3 spills per bathing season

sensitive areas <=6 spills per year

less sensitive areas but with recreation uses or popular footpath <=10 spills per year

less sensitive areas <=30 spills per year

The data reported to ERSAR under the scope of the quality of service assessment provided by the

operators in 2012 is represented in the next graphic:

It is observed that the most of operators that had unsatisfactory evaluation in the PI is due to a lack

of daily monitoring of their dischargers, as next graphic shows:

As a conclusion, the needs for further development to reduce the magnitude, frequency and duration of the discharges and their impacts on receiving waters require further development regarding:

• licensing the discharges according to receiving water characteristics;

• implementing systematic monitoring, may be used simple monitoring techniques, like “Chalk board” or “Bottle board” ;

• evaluation of the need for additional infrastructures (detention basins).

DIS

CH

AR

GE

S

Occasional

Continuous

Overflows in the network

and by-pass of PS and

WWTP)

Emergency (PS and

WWTP)

AR13 – Emergency Control

Discharges (%)

Without treatment

With treatment

AR12 – Proper treatment of collected

wastewater (%)

AR14 – Wastewater analysis (%)

AR15 - Compliance with discharge

parameters (%)

Figure 1 – Performance indicators used by ERSAR to evaluate each type of discharge

0

20

40

60

80

100

Nu

mb

er o

f d

isch

arge

rs

Operators

Number of dischargers and dischargers not monitored

Number of dischargers in PS and WWTP Number of dischargers not monitored

0

10

20

30

40

50

60

70

80

90

100

AR

13

-Em

erg

en

cy C

on

tro

l Dis

cha

rge

s (%

)

Operators

Quality of service assessment in 2012

81% of operators2% of operators

17% of operators

The control discharges in sewerage services has already been required in several EU

directives, in particular::

• Council Directive 91/271/EEC of 21 May 1991

• Directive 2000/60/EC of 23 October 2000 - Water Framework Directive

• Directive 2004/35/CE of 21 April 2004

However, there are some difficulties in controlling discharges, including:

• Knowledge of the sewer system;

• Response of the system to various precipitation events;

• Characteristics of the overflows and

• Receiving water quality impacts

The control of the discharges of raw wastewater and storm water has evolved very

differently in the various Member states. While discharges from treatment plants are

licensed in all Member States, the same is not true for intermittent wet weather

discharges. In many cases, no license is yet required and the control is

accomplished usually by limiting the frequency of discharges.