Waste Water Treatment Expert System

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Infocommunications technologies and applications IKTA4-00113/2001

Research & Development Division, Ministry of Education, Hungary 1

WASTEWATER TREATMENT EXPERT SYSTEM

Duration of the project: April 2002 November 2003

Home page of the project: pl. Co-ordinator:

University of Veszprm, VeszprmHome page: Address: H-8200 Veszprm, 8-10. Egyetem Str. Tel.: (36-88)-422022Project leader: rpd Krpti PhD., e-mail, Deputy project/team leader: Endre Domokos, e-mail,

Consortium member(s):

EuroTrend Informatikai Kft., 1141 Budapest, 5-7. Komocsi Str.

Home page: Team leader: Sndor Pejk, a tmavezetneve, e-mail,

Keywords: (sewage, purification, modelling, simulation, operation-control)

1. Aim of the project

The primary aim for the project is to create a complex expert system and database for

optimizing the design and operation of municipal sewage treatment plants in Hungary. The

project requirements call for the system to be able to:

choose the proper treatment technology, design the main size and operational parameters, calculate the cost of construction, operation, process control and

optimisation of the operation.

In developing the sewage treatment capacity in Hungary (primarily activated sludge

systems) this expert system will be a useful tool for many stakeholders in the process.

Authorities tasked with permitting, local governments seeking to improve sewage treatment

and companies that build and operating these technologies will all benefit from this expert

system.

2. Rationale

Developing this system for Hungary is highly important, as accession to the EU requires a

huge expansion and reconstruction effort. The local governments of small communities often

lack expertise both in scientific and technical knowledge regarding sewage treatment. These

local governments may also lack knowledge and experience in applying for financial

assistance from the State, the EU or other funding sources.

For Hungary, a serious problem is that since 1985 there have been no new design

guidelines or proposals set by the responding standardization authorities. As such, the


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permitting authorities have no measures in their hands to evaluate and differentiate the

proposals of the different designers and constructors.

The situation often exists that a local government lacks the skill needed to critically

evaluate technical design and construction proposals and make the best selection for the localcommunity. These proposals often contain only construction costs and deadlines but rarely

deal with operational costs. Choosing the less costly construction proposal frequently results

very high treatment costs far exceeding the savings of the initial investment. Effluent quality

guarantees from the designer and constructor may be dependent on operating parameters that

raise treatment costs to unacceptable levels. As a result of an ill informed decision and

contractual agreement, excessive operating costs may require process changes which void the

effluent quality guarantee from the builders. As a result the facility does not operate as

designed, effluent quality is worse and the environmental impact is greater.

The expert system would help avoid such problems by providing a tool for the

representatives of the population to make better decisions regarding the optimum technologyfor their community. The local government could with careful consideration specify the

requirements of construction and performance contracts. It would also be valuable to the

permitting authorities as they regulate new publicly owned treatment works (POTW) and the

expansion of existing systems.

With the help of the expert system both the local government and the permitting authorities

will be able to better evaluate the adequateness of a proposal based on:

sewage flow, technological parameters, required effluent quality, design and construction costs and, long term operation costs.

Implementing the expert system can result in considerable savings. It will be a useful tool

for the local governments and responsible authorities as well as State Ministries in developing

the proper capacities for the wastewater treatment in Hungary. As mentioned earlier,

accession to the EU requires Hungary to undertake large-scale improvements to the countriessewage treatment system. Because of the scale of the improvements needed, every effort

must be made to economize on costs. The local governments responsible for the sewage

treatment can save money on operational costs. The using population must pay these costs.

Construction costs can be saved for the central government budget, which covers large

portions of the initial investment. Approximately 60-70% of the construction is funded by the

central budget; the rest has to be financed by the local populations. This is why the

authorities and the administration of the Ministries as well as the local authorities must

control these costs very carefully.

The sewage from one third of the population of Hungary is treated by around 650 publicly

owned POTWs processing 700 thousands m3

/d. A modest savings of ten percent on the


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pumping and aeration costs of this flow would yield a 3-5 million forint saving annually.

This savings alone is enough to justify the development and use of the expert system while

simultaneously fulfilling effluent quality requirements. There is also the possibility for the

expert system to be expanded and applied to industrial wastewater treatment. This can further

result in considerable savings for the economy of the country and continue improvements ineffluent quality. This will require further development of the technical aspects of the expert

system, and validating its use in the practice.

This tool will include a dynamic process simulation able to model the operation of the

plant and the quality of the effluent. It can be used during design and planning for

optimisation of the operation, and minimizing the running costs (mainly aeration and

pumping energy). On the basis of the dynamic simulation of the wastewater treatment

processes, the expert system will be able to optimise the operation of currently operating units

as well as proposed units. The optimisation of energy use alone can result in savings of 40-50

% in electric energy consumption. Optimization of treatment performance is possible as well.

By simulating changes in operational parameters it may be possible to treat effluent to belowrequired values.

Additionally simulations with the expert system can evaluate the necessity of retrofitting

and upgrading the operating units. It can show the operator:

extension possibilities without overloading the plant capacity savings, the effect of small technological modifications without expensive pilot plant

experiments.

Running these simulations does not require extra knowledge of sewage treatment. They

require only minimal information and practice in computer use by the operator.

Choosing the optimum in cost and performance of sewage treatment facilities should be

the goal of local governments, regional permitting authorities and the Hungarian central

government. Decision makers at all of these levels can be aided by the expert system.

Entering into design and construction contracts, evaluating proposals for permitting

consideration and governmental Ministrys funds will all be easier with the help of the expert

system in the future than it is currently.

3. Results of the project

There were two main goals for the first phase of the project:

Developing a logical system for choosing technologies to fulfil statedrequirements.

Developing a dynamic simulator for design, and operational control of theprocesses.

Initially only the activated sludge or suspended growth systems were chosen for modelling

and simulation, as more than 90 % of the Hungarian plants have this type of technology. This


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proportion varies by country, as it is strongly dependent on the environmental policy,

regulation system and requirements of the specific country. In EU countries, sewage plants

with capacity less than 2000 PE (1000 in Austria) have no regulatory requirements for

treatment efficiency. The expert system is design to evaluate only the operation of plants

bigger than that size. The widely used wetlands and similar natural treatment systemstheoretically can not be used in Hungary at this time, as the ammonium limit for the treatment

is 10 mg/l independent of the seasonal cycles and low winter water temperature.

To initiate the project first we made a review of the design procedures, technology

selection, and structuring the process. This was done for continuous and cyclic sewage feed

and aeration with plug flow and completely mixed tank / cascade systems. The carbon,

nitrogen and phosphorus removal processes and efficiencies were evaluated in detailed for all

of these scenarios.

3.1. Evaluating the practice of the sewage treatment in the country

In Hungary there are presently around 650 POTWs with capacity above 2000 PE. Of

these, only 50 have capacity for more than 50 thousand PE. Of the remaining POTWs, 200

have a capacity of less than 10 thousand PE. These are practically treating only municipal

sewage. For facilities below this size, the winter has serious effect for the water temperature

during cold years. This is quite normal especially in the eastern part of the country, which has

a continental climate. These small POTWs may have problems with nitrification at low

temperatures. For these plants we can propose some extension, restructuring, better isolation

and better aeration in the critical periods.

3.2. Modelling a simulation

In this phase the detailed adapted mathematical model had to be set for the different reactor

and kinetics and phase separation solutions of the activated sludge systems. The model

evaluates varying control operation parameters and so optimises the sewage treatment.

Currently sludge processing (digestion and composting) is not included. As mentioned above

it is working in a user-friendly mode and so requires limited knowledge and technological

background and does not require advanced computer.

3.3. Operation control, and practical use

The use of the simulator is possible only for its developers at the moment. Within a few

months further software development will make it widely useful for the treatment plantpeople as well. The simulator can visualise the operation, and model changes of parameters of

the inflow and outflow at almost all operational units, i.e. the progress of the treatment within

the process. It is especially useful for teaching the personal of the plant, local government and

authority people and even visitors to the POTW.

The governmental and regional authority can also use the simulator. Before permitting any

new construction or reconstruction they can check the feasibility for the purpose of reaching

the requirements.

4. Necessity of extending the simulation and evaluation procedure


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In the near future the extension of the simulation program and software will be necessary.

It needs to be developed to handle in integrated form;

the sewage collection and sewerage system, treatment for given recipient quality or limits, by-product reprocessing and final use.

Final use of by products must be evaluated with proper care considering the end-use of the

nutrients of very slowly degradable residue. Effects on both the aquifer and the soil phase

have to be considered and simulated for the evaluation of the long-term sustainability of the

final use practices. Integrated wastewater management means the combined evaluation of the

treatment and the final disposal of the water, nutrients and other residuals. The multiphase

components (effluent, residues) and receiving environmental media (water, soil) necessitate

analogous modelling and simulation of these processes and cycles. Perhaps the proper controlof the soil phase will be the most problematic task. Data available regarding soil phase are

very highly dependent on the sampling location and will be difficult to integrate into the

expert system.

In addition to full life cycle assessment of POTWs, detailed evaluation with simulation has

to be extended to the wetland and other natural treatment systems. The same has to be done

for treatment of different industrial effluents and their residues. There currently are not

reliable composition and degradability data for such effluents, which complicates their

simulation.

In these industrial applications the anaerobic treatment or methanization of the biologicallydegradable mixed liquid semisolid solid wastes also has to be considered very carefully.

The solid residue is usually useful for composting, but the liquid by-product contains high

levels of ammonium, which makes it unacceptable for straight irrigation. Because of public

health concerns, the use of such liquid products of anaerobic digestion is often strongly

restricted.

For the biological removal of such concentrated ammonium containing sludge dewatering

liquid residues the newly developed autotrophic methods (SHARON and Anammox) are

really valuable but not fully industrialised. The same is currently true for the stripping of the

ammonium and its subsequent partial chemical oxidation incineration. These unit-processes

also need to be added to the expert system.

An analogous situation is the reuse of the liquid manure, or the filtration residue of the

manure. In this case there is no health based restriction of land application. In the case of

methanization of the suspended manure in mixture with other animal wastes, the regulations

and permitting requirements are confusing at the moment.

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Waste Water Treatment Expert System