Application of Continuous Improvement Strategy for reducing environmental impact of a wastewater treatment plant

Abstract

A modern and efficient wastewater treatment plant (WWTP) is obtained by improving not only the equipment and technology but also the management. The continuous improvement strategy (CIS) for the WWTP proposed in this paper is based on the principles of Six Sigma DMAIC (Define, Measure, Analyze, Improve, Control) and creates a new approach to reduce the defects and variations encountered in the processes of wastewater treatment plants by increasing the quality of information flow and decreasing quality costs. The analysis in the paper is focused on a municipal WWTP based on mechanical and biological nutrient removal technology on two lines, independently operating. The management team of the company has established as a target to reduce impact on the environment and the operational costs of the WWTP. In order to identify the project idea to achieve this goal, the Quality Function Deployment (QFD) was used. The main steps, the objectives and the activities of the process are established using the SIPOC diagram (Suppliers, Inputs, Process, Outputs, Customers). This helps managers to better understand the processes and it is a very valuable tool used in Six Sigma and Lean management concepts. Data collected from the WWTP during 2014 were analysed, taking into account the consequences, risks and impacts of the proposed solutions. The use of the bio-augmentation was selected as solution for improving the biological wastewater treatment process, reducing operational costs and reducing sludge production. Different doses of specialized microbial strains were added into the bioreactor in the period January-June 2015. Data collected during that period show a reduction of operational costs by 16.74%, compared with the respective in the same period of 2014.

Full text

Water Utility Journal 14: 29-40, 2016.
© 2016 E.W. Publications
Application of Continuous Improvement Strategy for reducing
environmental impact of a wastewater treatment plant
L.D. Robescu1*, C. Silivestru2, A. Presura3, A. Pana3 and R. Mihai3
1 Dept. of Environmental Protection Equipment, National Research & Development Institute for Turboengines –
Comoti, Bucharest, Romania / Dept. of Hydraulics, Hydraulical Machinery and Environmental Engineering,
University Politehnica of Bucharest, Romania
2 Dept. of Environmental Protection Equipment, National Research & Development Institute for Turboengines –
Comoti, Bucharest, Romania
3 S.C. RAJA Constanta S.A., Romania
* e-mail: diarobescu@yahoo.com
Abstract: A modern and efficient wastewater treatment plant (WWTP) is obtained by improving not only the equipment and
technology but also the management. The continuous improvement strategy (CIS) for the WWTP proposed in this
paper is based on the principles of Six Sigma DMAIC (Define, Measure, Analyze, Improve, Control) and creates a
new approach to reduce the defects and variations encountered in the processes of wastewater treatment plants by
increasing the quality of information flow and decreasing quality costs. The analysis in the paper is focused on a
municipal WWTP based on mechanical and biological nutrient removal technology on two lines, independently
operating. The management team of the company has established as a target to reduce impact on the environment and
the operational costs of the WWTP. In order to identify the project idea to achieve this goal, the Quality Function
Deployment (QFD) was used. The main steps, the objectives and the activities of the process are established using the
SIPOC diagram (Suppliers, Inputs, Process, Outputs, Customers). This helps managers to better understand the
processes and it is a very valuable tool used in Six Sigma and Lean management concepts. Data collected from the
WWTP during 2014 were analysed, taking into account the consequences, risks and impacts of the proposed
solutions. The use of the bio-augmentation was selected as solution for improving the biological wastewater treatment
process, reducing operational costs and reducing sludge production. Different doses of specialized microbial strains
were added into the bioreactor in the period January-June 2015. Data collected during that period show a reduction of
operational costs by 16.74%, compared with the respective in the same period of 2014.
Key words: wastewater; management; continuous improvement strategy; bio-augmentation
1. INTRODUCTION
The wastewater treatment technology is a very complex succession of unit processes, each of
them designed to remove a specific pollutant from wastewater (Robescu et al., 2011). Wastewater
operators should provide good quality effluents at costs as low as possible, under a more restrictive
legislation. There are a number of problems they have to be faced, from covering energy costs to
finding financing solutions for rehabilitation, modernization or expansion. Moreover, one of the
main problems in a WWTP is the resulted sludge that has to be treated.
One of the main causes of the Black Sea pollution is the inefficient treatment of the municipal
and industrial wastewater. All countries with direct access to the Black Sea region have concerns
about the modernization or construction of new wastewater treatment facilities. A modern and
efficient wastewater treatment facility (WWTP) is obtained by improving not only the equipment or
technology but also the management and personnel skills.
Bodoh (2006) researched reduction of chloride in wastewater treatment by using Six Sigma. In
Meisel et al. (2007) and UN Water (2015) there are examples of how Lean Six Sigma lead to
improving wastewater treatment performance and reducing cost. Boruath and Nath (2015) present
an application of Six Sigma methodology (DMAIC) for Effluent Treatment Plant in order to reduce
phenol concentration in the treated effluent. Howey and Middleton (2015) demonstrated the
application of Lean Six Sigma tools in a project undertaken by Seqwater. Ghassemi and Saghaei

30 L.D. Robescu et al.
(2014) showed that using Six Sigma led to costs reduction in the water and wastewater company.
The US Environmental Protection Agency (2012a, 2012b) published guides for improving
management in the water sector with case study examples.
Continuous Improvement Strategy (CIS) is inspired from Six Sigma, Lean, Kaizen and Total
Quality Management (Silivestru et al., 2014). It sets a new approach of reducing the defects and
variation in wastewater treatment facility processes, by increasing the information flow and
decreasing the costs of poor quality. To achieve this result, the continuous improvement strategy
requires an innovating management approach, by using the best techniques, tools and practices
inspired by the previous existing models and adapting them to any WWTP specificity. Unlike other
continuous improvement models, CIS is a way of doing business that focuses on constant efforts to
improve WWTP services quality to meet beneficiaries (customers) requirements and long-term
objectives. CIS focuses on making both incremental improvements and large process re-design
processes with the goal of increasing value to the final beneficiary.
The successful CIS implementation depends on an interaction between the following principles:
§ CIS is a primary tool for positive change used to improve any process developed by a WWTP
§ CIS is a disciplined methodology based on deploying continuous improvement projects.
§ Looking at WWTP activity from the customer’s perspective.
§ Looking at the processes from outside to identify the issues for improvement.
§ Highly visible top-down management that is committed to the initiatives of continuous
improvement.
§ Continuously improving all the processes in a WWTP. This means empowering people to
tackle problems as soon as they arise in the process, it will prevent the problem to escalate.
Improvements in the early steps of a process have a positive effect on later steps in the
process.
§ Provision of CIS training (methods and tools) to all wastewater treatment plant levels.
§ Adapting the WWTP's culture to enable the sharing of ideas from everyone from everywhere
in order to decimate the bureaucracy and make border-less behavior a reflexive and natural
part of its culture.
The implementation of CIS is based on developing individual projects but the success of this
strategy is achieved through a coordinated approach that is linked closely to the goals of the
WWTP.
Different wastewater treatment plants have different needs and abilities to implement CIS but the
need for continuous improvement depends on the following common factors: business environment;
wastewater treatment processes; organizational factors.
Executive Board for CIS coordinates the leadership and the implementation of continuous
improvement strategy.
The continuous improvement projects are based on the DMAIC methodology that consists of
deploying projects in five phases: Define, Measure, Analyze, Improve and Control.
2. CIS PILOT PROJECT AT CERNAVODA WWTP
The pilot CIS project is focused on a municipal WWTP operated by S.C. RAJA Constanta S.A.,
one of the biggest water companies in Romania.
WWTP Cernavoda is located at approx. 1.5 km north of the town, near the outlet channel of
Nuclear Power Plant (NPP) Cernavoda. It is designed to treat domestic wastewater from the
separate sewage network of the town, for a medium wastewater flowrate of 160 L/s. The effluent of
the WWTP is discharged in the outlet channel of NPP Cernavoda.
The wastewater treatment technology is mechanical - biological nutrients removal one of two
lines, each of them independently operating at a capacity of 100 L/s maximum daily flowrate.
The physical treatment stage comprises two compact units for fine screening and grit and grease
removal. After preliminary treatment, raw sewage pumps lift the flow into bioreactors. The

Water Utility Journal 14 (2016) 31
biological treatment stage has two independent bioreactors that can simultaneously operate. Each
bioreactor is based on Anaerobic/Anoxic/Oxic (A2 O) process in order to remove both organic
compounds and nutrients from wastewater. Air for nitrification and organic compounds removal is
supplied by three blowers. For effectively adjusting airflow (according to the required dissolved
oxygen concentration in bioreactors) one blower has variable speed.
Each bioreactor corresponds to a settling tank which is designed to separate activated sludge
from water. Settling tanks, as bioreactors do, can work simultaneously or independently. There is a
by-pass between the two settling tanks, for exceptional cases. A pumping station for returned sludge
and a pumping station for wasted sludge have been added to the system.
Designed sludge treatment technology is based on thickening, anaerobic digestion and
dewatering of digested sludge. For the moment, the anaerobic digester has not been yet put into
operation. The sludge is aerobically stabilized in bioreactors, then it is thickened, dewatered and
finally stored on the storage platform.
All equipment in the wastewater treatment plant can be operated both locally as well as
remotely. The processes are monitored by a SCADA system.
2.1. Define phase of the CIS project
The goal of the DEFINE phase is to select a well-bound continuous improvement project and
determine the strategy to complete it. This phase clearly states the problem that will be solved
through the project, reducing any replays and the project cycle time.
The specific objectives of this phase are: to identify the process for improvement; to identify
customers’ needs and translate them in internal key characteristics; to describe the preliminary
problem for improvement; to assess the project goal; to select the team and define the roles; to
define the high level process map; to obtain the approval of the project.
DEFINE phase of the project contains the number of pages considered necessary. It is mandatory
for each project to have a standardized summary for an easier collection and recording of the
information about the CI projects developed in the WWTP. The second standardized page presents
the team members, their names, position, CIS training and their signature. Training regarding CIS
and the DMAIC concept implementation is performed by a project leader, during the deployment of
the CI project. The third sheet keeps the records for the evaluation of the project status. This
evaluation is performed periodically by the CIS manager to check whether the project is carried out
according to the planned deadlines.
Each WWTP should have its own CI projects database created with the available software. This
database supports the CIS effort by supplying at least the following information: status of the CI
projects; project description; project objective; project leader; sharing of best practices; financial
benefits. The project leaders are responsible for recording the project and updating the database.
Project identification is the initial phase of any project; it includes a clear survey of the constraints,
a detailed analysis of ways and means, and a realistic review of resources in a specific social,
economic and legal frame.
The project identification phase analyzes the constraints, existing strategies and needs evaluating
the effort (time and resources), determining the opportunities, developing partnerships, evaluating
the risks and alternatives. It is important because in this phase the most efficient and cost-effective
methods are identified. The project identification requires vision, creativity, careful analysis, a
thorough cognition of the general environment and, of course, debates.
The management team of the water company has established as a target to reduce environmental
impact of the WWTP Cernavoda. In order to identify a project idea to achieve this goal the Quality
Function Deployment (QFD) method was followed (Robescu, 2015). That method is usually used
by industrial companies, but it could be adapted to the management of WWTPs.
QFD is a matrix format that includes customer requirements, technical requirements, a planning
matrix, an interrelationship matrix, a technical correlation matrix, and a targets section. After the
House of Quality Matrix is created, taking into account the processes of the plant, the manager

32 L.D. Robescu et al.
identify what improvement can be made in order to reduce the impact of the WWTP and the
operational costs.
2.1.1 Quality Function Deployment
The main steps in creating QFD are shown in Table 1:
1. Establishment of customer requirements; they represent the answer to the question “What is
desired by the customer to improve the environmental impact of WWTP Cernavoda?”
2. Definition of “How”. The CI Project team defines the technical requirements satisfying
customer’s expectations and inserts them in the House of Quality (HQ) matrix.
3. Establishment of the importance level of customer requirements (“WHAT”). The relative
significance of ‘what’ is stated through an evaluation by the customer. The relative scale used
ranges from 1 to 5 setting up that ,as customer importance is seen as more significant, the
larger the number is. They are mentioned in the HQ.
4. Classify the importance of the relationship between each “How” and each “What”. They are
written in HQ matrix. The scale used is: Low = 1; Medium = 5; Strong = 9; No correlation = -
5. Calculate the importance level of “HOW” to approximate the most important technical
descriptors for customer satisfaction. This creates a value for each relationship between
customer and technical descriptor. The importance of “How” is calculated by adding the
values together and writing them in HQ matrix.
Table 1. QFD for improving impact on the environment of WWTP Cernavoda.
Technical
requirements
Customer
requirements
Advanced
wastewater
treatment
Type of
biological
process
Automatic
control of the
processes
Covering objects
and odor control
Advanced
dewatered of
sludge
Using
bioaugmentation
Using silencers
Energy
efficiency
program
Green spaces
Sludge storage
condition
Importance level
Effluents discharge in
line with legal
requirements
9
9
5
-
-
5
-
1
-
-
5
Reducing quantity of
the sludge
5
9
1
-
9
9
-
-
-
-
5
Reducing organic
loading of the sludge
5
9
1
-
-
5
-
-
-
-
5
Reducing odors
5
9
1
9
1
9
-
-
5
9
4
Reducing noise
-
1
1
-
-
-
9
-
1
-
2
Reducing energy
consumption [kWh/m3
treated wastewater]
1
5
9
-
-
5
-
9
-
-
5
Lack of insects
5
5
1
9
1
1
-
-
5
9
3
Reducing GHGs
5
5
5
9
-
1
-
9
5
5
5
160
238
114
108
52
164
18
95
62
88
As it can be seen from Table 1, the main technical requirement to improve the impact on the
environment of the WWTP Cernavoda is using bioremediation, since the WWTP is already built so
this is the only possible solution to change the biological process.
2.1.2 CIS implementation - SIPOC diagram
In order to identify the major steps, targets and activities in the process to be improved, the
SIPOC (Suppliers, Inputs, Process, Outputs and Customers) diagram is used (Table 2), as proposed
by Robescu (2015). It is a tool that helps the WWTP managers to understand better the processes,

Water Utility Journal 14 (2016) 33
but it is also very useful for the entire team to gain a common understanding of the processes
developed by the treatment plant.
SIPOC is introduced in the CIS in the DEFINE phase due to its simplicity and ability to capture
the current state of the process that must be improved. SIPOC diagram is completed in the
following steps:
Step 1: The manager of the WWTP selects the process to be improved;
Step 2: Forms the appropriate team with the people involved in this process;
Step 3: Obtains team consensus about the necessity of improvement;
Step 4: Defines the main steps of the process.
Table 2. SIPOC diagram for CIS pilot project implementation
SIPOC – “Improving impact on the environment of WWTP Cernavoda using bioaugmentation”
Suppliers
Inputs
Process
Outputs
Customers
START
Municipal wastewater
Settling tanks
Bioaugmentation tabs
distribution company
Electricity Supply
Company
Wastewater treated in
physical stage
Recirculated sludge
Bioaugmentation tabs
Electric current
Biological
reactors
Biological treated
wastewater
Settling tanks
Biological reactors
Electricity Supply
Company
Biological treated
wastewater
Electric current
Settling tanks
Settled sludge
Clarified water
Pumping station for
recycled and wasted
sludge
Pumping station for
wash water
Effluent
Settling tanks
Electricity Supply
Company
Settled sludge
Pumping station
for recycled and
wasted sludge
Recycled and wasted
sludge
Bioreactors
Mixing tanks for
wasted sludge
Pumping station for
recycled and wasted sludge
Electricity Supply
Company
Wasted sludge
Electric current
Mixing tanks for
wasted sludge
Mixed wasted sludge
Centrifugal sludge
thickening
Mixing tanks for wasted
sludge
Polyelectrolyte preparing
and dosing plant
Electricity Supply
Mixed wasted sludge
Cationic polyelectrolyte
Electric current
Centrifugal
sludge
thickening
Thickened sludge
(approx.4.5 % DSS)
Wastewater returned
into bioreactor
Centrifugal sludge
dewatering
Bioreactor
Centrifugal sludge
thickening
Polyelectrolyte preparing
and dosing plant
Electricity Supply
Company
Thickened sludge
Cationic polyelectrolyte
Electric current
Centrifugal
sludge
dewatering
Dewatered digested
sludge (aprox. 24%
DSS)
Wastewater returned
into bioreactor
Sludge storage
platform
Bioreactor
Centrifugal dewatered
sludge
Dewatered digested
sludge
Sludge storage
Dewatered digested
sludge
Landfill of
Cernavoda city
STOP
Step 5: Define the outputs of the process. These are effective things desired by the customer or
tangible results desired by an internal customer, in order to satisfy the final beneficiary
of the services ensured by a wastewater treatment plant;

34 L.D. Robescu et al.
Step 6: Identify the internal or external customers receiving the outputs of the process;
Step 7: Define the inputs to the process: the data, knowledge and resources necessary for the
process to deliver the required output;
Step 8: Identify the suppliers of the inputs required by the process.
After the completion of the SIPOC diagram, the improvement team begins to analyze the
opportunities for accomplishment of project objective. It is obvious that improvement of impact on
environment would be achieved by reducing the energy consumptions and the sludge production in
bioreactor. This can be done using bio-augmentation tabs. It was set that the project objective is to
reduce the operational costs of the WWTP by at least 15% using bio-augmentation.
2.2. Measure and analyze phases of the CIS project
Pursuing the DMAIC methodological cycle, after completing the DEFINE phase, managers
continue their improvement strategy by initiating a research to determine the performance of the
current process and concentrate their efforts to identify the root causes of the problems to be
eliminated (Silivestru et al., 2015a).
Measure phase prepares the process for change, by monitoring its actual performance and
variation points. Establishing the baseline of the process is a key-aspect of CIS, since it will lead to
a standard dataset utilized in making the relevant comparisons with future improvements. The
WWTP managers frequently have access to large masses of potentially useful data that could help
them to make the best decisions. But these data must be organized, processed and evaluated by
some statistical techniques before being used in managerial decisions.
2.2.1 Data collection
Data collecting is one of the key issues that must be solved by the project team in the Measure
phase. The values measured for these characteristics are used to establish the performance of the
baseline process, therefore, collecting data is a major objective of the Measure phase.
WWTP develops a CI pilot project to reduce operational costs using biotabs for bio-
augmentation.
Once the project team established this operational definition for the measurements that must be
done, they should elaborate the data collection plan for the year 2014. It includes five set of data:
§ data for influent and effluent of WWTP: flowrate, temperature, pH, DO (dissolved oxygen),
TSS (total suspended solids concentration), extractable solids concentration, COD (chemical
oxygen demand), BOD (biochemical oxygen demand), total phosphorus, total nitrogen, NO3,
NO2, NH4, fixed residue;
§ data for activated sludge and recirculated sludge in biological reactors: pH, temperature, DO,
DSS (30 min) dry suspended solids concentration, TDSS (total dry suspended solids
concentration), SVI (sludge volume index), MDS (mineral dry solids concentration), VDS
(volatile dry solids concentration)
§ data for wasted, thickened, respectively dewatered sludge: flowrate [m3/day], DSS [%]
§ power consumptions for aeration, thickening and dewatering of the sludge and total power
consumption of WWTP
§ polyelectrolyte consumption for thickening and dewatering of the sludge.
2.2.2 Analyze of data
In the Analyze phase, the project team examines the data using specific statistical tools and
Cause and Effect Diagram presented in Fig.1. The main goal is to identify all sources of possible

Water Utility Journal 14 (2016) 35
variation that contribute to the variation of the key characteristic selected in the Define phase, that
are the operational costs. The project team separated the causes most likely responsible for the
variation from the trivial ones. The improvement efforts had been focused on the vital cause
represented by biomass characteristics in biological wastewater treatment stage.
Figure 1. Cause and Effect Diagram.
The following notations are made in Figure 1: SS- suspended solids concentration; Dep_NA –
suspended solids concentration in activated sludge; Dep_NR – suspended solids concentration in
recycled sludge; IVN_NA – sludge volume index for activated sludge; IVN_NR – sludge volume
index for recycled sludge; Q_NR – flowrate of recycled sludge; SRT – sludge retention time; MLSS
– mixed liquor suspended solids concentration.
Conclusions from the measure and analyze phases are:
§ the main power consumptions are related to biological stage;
§ influent flowrates of the wastewater have a large variation reflected in the power consumption
of the blowers;
§ future improvement will be on the biological stage in order to reduce power consumptions,
sludge production and consequently operational costs.
2.3 Improve and control phases of the CIS project
Improve and Control are the last phases of the methodology DMAIC that ensure the
implementation and the sustainability of the improvements with minimal cost and maximum
efficiency (Silivestru et al., 2015b).
2.3.1 Improve phase
Improve is the most challenging phase because in that phase the results of the entire effort done
were obtained and the manager can implement changes to improve the process.
The project team found the best solutions to act on the causes of variation and to deliver the
required improvements. The final decision was taken by the project team leader together with the
CIS manager and the top manager of the wastewater treatment plant. They hold a list with the
prioritized solutions, which had resulted from a previous brainstorming, and they analyzed again the

36 L.D. Robescu et al.
proposed solutions having in mind their own evaluation criteria. They select the best solution taking
into account the consequences, risks and impacts of the proposed solutions and agree with the
project team solution. In this case, the best solution selected was the use of bio-augmentation.
First, the project team studied the documentation regarding bio-augmentation and chose an
external bio-augmentation method that is seeding from commercial sources of microorganisms.
Then, it the team selected a product supplier, the applying procedure was set up and the plan for
carrying out the procedure was established.
Specialized microbial strains were added into the bioreactor in order to enhance the ability of the
microbial community to respond to process fluctuations. The sources of microorganisms were
tablets and granular containing various strains of non-toxic, and non-pathogenic bacteria (Bacillus
and Pseudomonas), sodium percarbonate, sodium peroxycarbonate, biological surfactants, nutrients
and binders.
Different doses of biotabs were applied during January - May 2015. The same data collection
plan proposed in the Measure phase was established and the results for year 2015 were compared
with those for year 2014.
The specific data for a month represent the average value obtained from the measured data
during that month. This was chosen as the most appropriate method of representation, as not all data
are daily measured. For example, the wastewater flowrates and loadings are measured daily, but the
power consumptions or sludge production is measured only two or three times in a month. All the
data are presented using Minitab statistical software.
The variation of influent wastewater flowrates is presented in Figure 2 and of influent and
effluent BOD, respectively, in Figure 3. It can be observed that the WWTP effluent BOD
concentrations comply with Romanian regulations, 25 mg/L, but the use of biotabs in 2015 led to
reduced concentrations.
Figure 2. Variation of influent wastewater flowrates, [m3/day].
It was observed that the sludge production decreased when the biotabs were used and in March
and April 2015 it was not necessary to waste the sludge (Figure 4).
Consequently, the polymer consumption decreased (Figure 5), leading to 53.21% reduction of
costs per month. Also, the power consumption for sludge treatment decreased by 60.77% per month
(Figure 6).

Water Utility Journal 14 (2016) 37
Figure 3. Variation of influent and effluent BOD [mg/L].
Figure 4. Variation of wasted sludge flowrate, Q_Nex [m3/month].
Figure 5. Variation of polymer consumption, [kg/month].

38 L.D. Robescu et al.
Figure 6. Variation of energy consumption for sludge treatment, [kWh/month].
It was noticed that blower power consumption decreased by 16.49% and the total power
consumption of the wastewater treatment plant by 16.6% per month, as seen in Figures 7 and 8. The
total operational costs of WWTP decreased by 16.74%.
Figure 7. Variation of energy consumption for blowers [kWh/month].
Figure 8. Variation of total energy consumption of WWTP [kWh/month].

Water Utility Journal 14 (2016) 39
2.3.2 Control phase
Control is the last phase of DMAIC methodology adopted by CIS in order to ensure the
sustainability of the improvements done in the previous phase. The Control phase of any CI project
developed in a WWTP must assure the permanence of the advantages obtained in the Improve
phase, a long while after the project has ended. The wastewater treatment sector has a high risk
exposure, involving both environmental and human consequences.
In this phase, the team identified the risks that might occur and could lead to loss of performance
of the improved process using Failure Mode and Effects Analysis (FMEA). It represents the
systematic method of identifying and preventing product and process problems before they take
place, and is very valuable in helping companies to achieve high reliability in products or processes
at lower costs and shorter development times.
The FMEA team comprises 4 members acquainted with the treatment process and with the
ability to visualize and anticipate most of the problems that could occur during system operation.
The team has made a list of potential failure modes, which might occur in the biological process.
All possible effects of failure modes were analyzed and identified, with the approval from all
team members.
All failure modes were granted the Severity, Occurrence and Detection rates in order to have a
clear picture of the possible failures that can affect the biological process and their impact on
Cernavoda Wastewater Treatment Plant’s performance.
The Risk Priority Number (RPN) was calculated for each failure mode – RPN = Severity x
Occurrence x Detection. They were prioritized by arranging them from highest to lowest, thus
visualizing the rating differences in order to decide which aspects are the most important.
After debating every possible failure, the team made recommendations regarding associated
preventive actions. A person in charge for applying new measures for each recommended action
was appointed out of the team members.
After performing the recommended preventive actions, the FMEA team must re-evaluate the
severity, occurrence and detection rates in order to analyze the improvements brought to risk
priority numbers. Failure modes were re-evaluated and the FMEA team managed to significantly
improve occurrence, visibility and severity.
3. CONCLUSIONS
The Continuous Improvement (CI) principles outline an integrated strategy for process
improvement, by searching and removing the causes of defects and variables; they also frame a
continuous and qualitative improvement strategy, which involves the commitment of the entire
working team. CIS concept corresponds to the need of regional operators and WWTP managers to
obtain a better monitoring of treated wastewater, costs reduction, identification of time-consuming
activities and beneficiaries satisfaction.
The vision of any WWTP that is implementing CIS is to be a leader on the wastewater market or
to develop an excellent reputation. The policy of a such WWTP must clearly stipulate the need to
continuously improve the plant's performance on quality, environment, health and safety at work.
The paper presents the pilot CIS project in Romania that has the main objective to reduce
environmental impact and operational costs of the WWTP Cernavoda. The study shows that CIS is
a proven and good tool for quality improvement purposes in WWTP. Application of CIS concepts
leads to a solution for reducing sludge production, power consumptions, polymer consumption and
consequently for reducing operational costs of the WWTP.
ACKNOWLEDGEMENTS
This work was supported by Joint Operational Programme “BLACK SEA BASIN 2007-2013”,

40 L.D. Robescu et al.
project “Continuous improvement strategy for increasing the efficiency of wastewaters treatment
facilities in the Black Sea coastal states – CISWastewater”, 2.2.3.72546.202, MIS ETC 2177.
An initial version of this paper has been presented in the WASTEnet Program Conference,
“Sustainable Solutions to Wastewater Management: Maximizing the Impact of Territorial Co-
operation”, Kavala, Greece, June 19-21, 2015.
REFERENCES
Bodoh, M.J., 2006. Reduction of chloride in wastewater effluent with utilization of Six Sigma, A research paper submitted in partial
fulfillment of the requirements for the Master of Science Degree in Technology Management, The Graduate School, University of
Wisconsin-Stout
Boruah, M., Nath, T., 2015. Application of Six-Sigma Methodology in Effluent Treatment Plant. International Journal of
Engineering Research & Technology, 4(9): 589-594
Ghassemi, M., Saghaei, A., 2014. Implementing Six Sigma for cost reduction in the water and waste water company, Journal of
Current Research in Science, 2(6): 590-598
Howey, J., Middleton, D., 2015. Lean Six Sigma application to water utilities: getting value for money out of water quality
monitoring, Ozwater 2015, retrieved from http://www.awa.asn.au/documents/068%20JHowey.pdf
Meisel, R.M., Babb, S.J., Marsh, S.F., Schlichting, J.P, 2007. The executive guide to understanding and implementing Lean Six
Sigma: the financial impact, ASQ, Quality Press
Robescu, L.D., 2015. Improvement project to be implemented in a Romanian WWTF, project “Continuous improvement strategy for
increasing the efficiency of wastewaters treatment facilities in the Black Sea coastal states – CISWastewater”, 2.2.3.72546.202,
MIS ETC 2177, Dobrich meeting, Bulgaria
Robescu, L.D., Stroe, F., Presura, A., Robescu, D, 2011. Tehnici de epurare a apelor uzate (Technics for Wastewater Treatment),
Editura Tehnica, Bucuresti
Silivestru, C., Ifrim, D., Gugu, A.M., Mihalache, R., 2014. Define Manual, MIS ETC 2177
Silivestru, C., Ifrim, D., Cirstea, A.M., Mihalache, R., 2015a. Measure and Analyze Manual, MIS ETC 2177
Silivestru, C., Ifrim, D., Cirstea, A.M., Mihalache, R., 2015b. Improve and Control Manual, MIS ETC 2177
UN Water, (2015). Wastewater Management. A UN-Water Analytical Brief, retrieved from http://www.unwater.org/fileadmin/
user_upload/unwater_new/docs/UN-Water_Analytical_Brief_Wastewater_Management.pdf
United States Environmental Protection Agency, 2012a. Resource Guide to Effective Utility Management and Lean Improving
Performance and Addressing Key Management Priorities at Water-Sector Utilities, retrieved from www.epa.gov
United States Environmental Protection Agency, 2012b. Lean & Water Toolkit, Achieving Process Excellence Through Water
Efficiency, retrieved from www.epa.gov/lean