Avløpsanlegg

9 / 72

9
English summary
This report is published in Norwegian by Norwegian Water BA (Norsk Vann BA), /
ISBN: 978-82-414-0347-7
Summary:
This guideline describes the process of environ-
mental risk assessment and management regarding
emissions to the environment from wastewater
systems (sewage system and waste water treatment
plants (wwtp)). It has been written as an aid in the
reduction of the consequences of the emissions and
to mitigate further acute accidental and planned
emissions. The elevated risk caused by climate
change is also included. The guideline provides an
introduction to the work methodology based on the
Norwegian standard ”Requirements for risk assess-
ment” (NS 5814:2008). The work flow has three
phases: planning, risk analysis and risk evaluation
including plans of actions. The risk analysis is based
on the methodology termed ‘Risk Analysis and
Vulnerability’ (RAV). Environmental Risk acceptance
criteria are grouped into high, medium and low risk.
By using a risk matrix, risk is quantified by multiply-
ing the probability of an incidence with a number
for the consequences to the environment.
The guideline describes a process oriented work
methodology for risk assessment by going through
the whole wastewater treatment processes and
discharge points. Vanndal is used as an example mu-
nicipality conducting an environmental risk assess-
ment. This gives an idea of how the environmental
challenges to the operation of the waste water sys-
tems are assessed, and how planning, systemising,
analysis and evaluation of the risk of the emissions
to the environment may be performed. Vanndal
municipality has various challenges that may effect
the environment. These include:
››Combined sewer systems cause periods with
hydraulic overload
››Frequent emergency overflow discharges caused
by flooded pumping stations
››Irregular organic loads in the wwtp
››Odour emissions from sludge treatment
››Vacant positions in the organisation
››Vulnerable river recipient - source for drinking
water downstream the discharge point
Other methods of analysis than RAV may also be
used, especially for more technical system compo-
nents as pumping stations. Risk assessments should
be updated periodically to ensure that medium and
high risks are managed and that new risk areas are
investigated.
Address: Vangsvegen 143,
N-2321 Hamar, Norway
Phone: + 47 62 55 30 30
E-mail:
Report no: 197 - 2013
Report Title: Wastewater Systems - Risk
assessment on the environment
Date of issue: 30.06.2013
Number of pages: 61 (66)
Author: Line Diana Blytt og
Elisabeth Lyngstad, Aquateam