Hungary has a critical wastewater management problem in that the majority of wastewater treatment plants (WTP) are overloaded and the quality of effluent water generally does not meet local, nation or European Union water quality standards. Establishment of new WTPs and enlargement of the existing ones are limited by financial constraints. One of the best approaches to improve the quality of sewage effluent, under these circumstances, is to improve the efficiency of existing biological WTPs without adding a significant operational cost.
The most often used wastewater method is aerobic biological treatment in which oxidizable contaminants are decomposed by bacteria in the presence of oxygen. The culture of bacteria forms a living activated sludge. The biological capacity of WTPs and the quality of treated wastewater depend on the activity and the settling properties of the activated sludge. These sludge parameters, however can considerably be improved with the addition of zeolite particles into the raw wastewater.
Zeolite particles of mm size are good carriers of bacteria and substrates. Since the oxygen and the adsorbed substrates are accessible in high concentrations for the bacteria immobilized on the zeolite particles, the decomposition rate of organic compounds becomes higher. Since the specific gravity of bacteria flocks containing zeolite is higher than that of usual flocks, the settling rate of the waste sludge will be better.
Application of a zeolite additive, in spite of the advantageous
effects, has a significant drawback. Positive effects of zeolite addition appear
only after a prolonged period (i.e., more than 24-hours). This can be explained
by the slow or inhibited biopolymer production of bacteria since bacteria attach
to the zeolite particles through their biopolymer chains.
In this project, a new zeolite modification method and a new wastewater treatment
technology are being developed in order to accelerate and improve the interaction
between zeolite particles and bacteria, as well as increase the loadability
of wastewater treatment plants, improve the quality of treated water and decrease
the investment and operation costs of WTPs.
The theory of the new zeolite modification method is based on the following reasoning:
Characteristics of the link created between the zeolite particles and the CAP molecules depend on the form, the specific surface area, the Si/Al ratio of zeolites, the zeolite/CAP ratio, as well as the type and the length (molecular weight) of the CAP used for modification. In the first project phase, the optimal parameters of the modification method were developed. Then the effects of modified zeolites on the decomposition rate of organic compounds were tested by laboratory experiments. In the second phase of the project, a large quantity of modified zeolite are being manufactured and pilot, as well as industrial scale experiments, are being carried out at several WTPs of differing influent characteristics using a modified zeolite.
The project as implemented is summarized in the following 12 tasks:
Task 1 Selection and investigation of zeolites ...
| 1.1 |
Collection of available data and/or determination
of the structure and the physical-chemical properties of Hungarian zeolites
- Mineral composition, cation exchange capacity, Si/Al ratio, specific
surface, of the Hungarian zeolitic rocks will be collected and/or measured. |
| 1.2 |
Selection of zeolites - Based on the properties two
Hungarian natural zeolites will be selected the clinoptilolite contents
of which should vary between 50 - 95 %, and the samples are to be mining
products. |
Task 2 Pre-treatment of zeolites selected
| 2.1 | Mechanical treatment - The zeolite bearing
rocks will be ground and the sieve fractions < 200 micrometer will
be selected. |
| 2.2 | Conversion to H+-form - The mechanically
treated (MT) zeolites will be treated with aqueous HCl solution of 1 mol/L
at room temperature. |
| 2.3 | Specific surface increasing and conversion to H+-form
- The MT zeolites will be treated with aqueous HCl solution at the boiling
point temperature. |
| 2.4 | Conversion to NH4+-form - The MT zeolites will be treated with NH4Cl solution of 0.5 mol/l at room temperature. |
Task 3 Modification of the pre-treated zeolites
| 3.1 | Modification with CAP containing quaternary
ammonium groups - Four differently pre-treated zeolites produced in Task
2 will be modified. |
| 3.2 | Modification with CAP containing amino groups – Four
different pre-treated zeolites produced in Task 2 will be modified. |
Task 4 Determination of the chemically bound CAP content of zeolites modified
| 4.1 | TOC measurement – Modified zeolites (MZ)
will be washed through with TOC-free water to remove the mechanically
adhered CAP molecules thereafter the TOC content of the MZ will be determined. |
| 4.2 | Infrared measurement - MZ will be examined by Fourier transform infrared spectroscopy. |
| 4.3 | Data evaluation - Based on the result of the experiments,
MZ having chemically bound CAP will be selected, the optimal conditions
of zeolite modification (type of pre-treatment, type of CAP, optimal molecular
weight of CAP and the optimal zeoliteew/CAPew ratio) will be concluded. |
Task 5 Classification of modified zeolites by respirometric experiments
| 5.1 | Measurement of the biological degradability
of a typical municipal wastewater – Experiments will be carried out with
and without zeolite addition in a continuous respirometer. MZ having chemically
bound CAP and basic zeolites (natural zeolite, zeolite of H+-form, zeolite
of H+-form and increased surface, zeolite of NH4+-form) will be used in
consecutive experiments. Zeolites and activated sludge originated from
a municipal WTP will be added to the wastewater. Quality of the treated
wastewater will be measured after 1, 2, 4, 8 and 12 hours. |
| 5.2 | Ranking of MZ – The effect of each type of MZ on
water quality will be economically quantificated. MZ resulting in the
largest economic advantage will be considered the best ones. Two MZ having
the best economic parameters will be used for further experiments |
Task 6 Biological degradability test of the wastewaters originating from the end-users selected
| 6.1 | Respirometric measurements - Biological degradability of wastewaters will be determined in the respirometer used in Task 5 without zeolite addition and applying the two MZ selected. The following relationships will be determined:
|
| 6.2 | Data evaluation - Based on the results of the respirometric experiments
|
| 6.3 | Determination of the technical specifications of
the mathematical model describing the physical-chemical processes taking
place in the bioreactor and introducing the impact of the zeolite additive
on water quality. |
| 6.4 | Evaluation of the economic effect of modified zeolite
addition (MZA). The economic advantages of the MZA regarding to the cost
of wastewater treatment will be calculated and the results will be introduced
to the end-users. |
Task 7 Manufacturing of modified zeolites
3.0 x 104 kg modified zeolite of the best characteristics will be produced for the pilot and full-scale experiments.
Task 8 Pilot-scale experiments
| 8.1 | Based on the laboratory-scale experiments, the technology using modified zeolite (ZeoRap) will be installed and set to work in the WTP s of two end-users. MZ of best characteristics will be applied in three different concentrations. The following work phases will be performed:
|
| 8.2 | Data evaluation - Based on the results of the respirometric experiments
|
| 8.3 | Calibration of the mathematical model |
| 8.4 | Evaluation of the economic effect of ZeoRap technology-
The economic advantages of MZA will be calculated in the form of operational
+ amortisation cost-savings and the results will be introduced to the
end-users. |
Task 9 Full-scale plant experiments
| 9.1 | The experiments will be carried out according
to Task 8, but in full-scale, in a WTP. Based on the results of the experiments,
relationships among the concentration of the modified zeolite, oxygen
uptake, effluent water quality and SVI, as well as the economic advantage
of the ZeoRap technology will be determined. |
| 9.2 | Technical documentation of the ZeoRap technology will be developed. |
Task 10 Dissemination of the project results
For the purpose of market penetration of the innovative US - Hungarian water treatment technology, called ZeoRap.
Task 11 Bi-annual progress reports
Task 12 Final report