ENVIRONMENTAL TECHNOLOGIES

Head office: Factory address: 67 Aiolou Str, 10559 Thesi Mavri Ora,19300 Athens, Greece Aspropyrgos, Greece Tel. +30 210 3211040, +30 210 3222825, fax +30 210 3222012 Tel. +30 210 5596060 e-mail: info@devise.gr website: www.devise.gr

CASE STUDY FOR A NEW PACKAGED-CONTAINERISED STP OF UPTO 3,425 m3/d

FOR WATER REUSE IN THE ISLAND OF CRETE – GREECE BY “DEVISE ENGINEERING”

DEVISE ENGINEERING SA specializes in the field of Environmental Technologies and particularly in the design, manufacturing, procurement, installation, and initial operation & monitoring of packaged (i.e. in containerized form) physical-chemical and biological treatment units for small- and medium-scale applications, both municipal and industrial Wastewaters.

DEVISE ENGINEERING SA through its partnering company MESOGEOS SA Contracting Group, has been awarded the contract for the design & build of Gouves STP (Municipality of Hersonissos, Prefecture of Heraklion) in the Island of Crete. The project includes the Design-Engineering, Construction, Start-up, Commissioning, Operation and Maintenance of this Sewage Treatment Plant. This STP is of one of the largest Packaged STPs in the region of South Europe & Mediterranean, with modular capacities up to 3,425 m³/d. This projected is implemented with Pre-fabricated Packaged Biological Treatment Units of Containerized form using the innovative DEVISE “UltraClear” Technology incorporating a Hybrid treatment method of submerged Ultra-Filtration Membrane Modules (MBR) and MBBR Technologies

The project is expected to be executed on a Fast-Track basis since the DEVISE “Smart Packaged Solutions” allowed it in order to cover the urgent needs of the touristic area of Gouves (Crete) located in a coastal area of the island. Furthermore, the treated effluent from the STP is going to be recovered and reused for land irrigation purposes so that the scarce fresh water resources of the island are not strained.

The basic design data for the aforementioned STP are summarized in Table 1, whereas the treated effluent quality requirements are shown in Table 2. While Table 3 summarizes the individual treatment steps that are incorporated in the selected overall process scheme.

Table 1 – Basic design data for the Gouves STP project

Parameter Unit Value

Winter Summer Future

Population Equivalent PE 4151 9000 13500

Daily Design Flow m3/d 598 2285 3425

Peak Hourly Flow m3/h 57 190

Water Temperature oC 15 20

Total Suspended Solids (TSS) mg/L 485 275

Biochemical Oxygen Demand (BOD) mg/L 415 235

Chemical Oxygen Demand (COD) mg/L 830 470

Total Kjeldahl Nitrogen (TKN) mg/L 70 40

Total Phosphorus (TP) mg/L 28 16

DEVISE ENGINEERING S.A. ENVIRONMENTAL TECHNOLOGIES

Head office: Factory address: 67 Aiolou Str, 10559 Thesi Mavri Ora,19300 Athens, Greece Aspropyrgos, Greece Tel. +30 210 3211040, +30 210 3222825, fax +30 210 3222012 Tel. +30 210 5596060 e-mail: info@devise.gr website: www.devise.gr

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Table 2 – Treated effluent quality requirements for the Gouves STP project

Parameter Unit Value

Total Suspended Solids (TSS) mg/L < 2

Biochemical Oxygen Demand (BOD) mg/L < 10

Chemical Oxygen Demand (COD) mg/L < 50

Total Nitrogen (TN) mg/L ≤ 15

Ammonium Nitrogen (NH4-N) mg/L ≤ 1

Total Coliforms (TC) CFU/100 mL < 2

Residual Chlorine (RC) mg/L < 0.5

Table 3 – Selected overall process scheme for the Gouves STP project

Treatment Step Treatment Objective

Liquid Stream

1. Pretreatment

Removal of gross solids

Separation of grit & sand

Retention of fat & oil

2. Equalization Balancing of hydraulic and constituent load variations

Complete wastewater mixing and homogenization

Prevention of septicity and excess odor development

3. Secondary Treatment Elimination of organics (BOD and COD)

Reduction of TN (nitrification / denitrification)

Separation of biomass from treated water

4. Tertiary Treatment Advanced removal of SS and colloids along with associated organic matter (particulate BOD and COD)

Preparation for effective disinfection

5. Disinfection Complete destruction of pathogens

Sludge Stream

1. Thickening Collection of waste sludge

Concentration of sludge

2. Dewatering Conditioning of pre-thickened sludge

Reduction of sludge moisture

DEVISE ENGINEERING S.A. ENVIRONMENTAL TECHNOLOGIES

Head office: Factory address: 67 Aiolou Str, 10559 Thesi Mavri Ora,19300 Athens, Greece Aspropyrgos, Greece Tel. +30 210 3211040, +30 210 3222825, fax +30 210 3222012 Tel. +30 210 5596060 e-mail: info@devise.gr website: www.devise.gr

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The pretreatment step comprises two (2) compact combined pretreatment units with provision for one (1) added or future expansion, that integrate 6-mm screening, degriting, and fat & oil separation and operate. By operating in parallel, the selected pretreatment units can readily accommodate the peak hourly flow during summer flow conditions.

The equalization (EQ) step comprises a covered underground reinforced concrete rectangular tank with 1000-m3 effective volume. Simultaneous sewage homogenization and pre-aeration is performed inside the EQ tank by means of a venturi jet aerator. Three (3) submersible centrifugal pumps are also installed in the EQ tank with a view to feeding the pretreated wastewater to the subsequent treatment step.

The secondary treatment step comprises four (4) parallel-operating (+ 2 future) packaged biological treatment units each having a maximum pretreated sewage capacity of 575 m3 per day. The overall feed flow is equally divided between the four parallel bio-units by means of a splitter box. Each bio-unit comprises two (2) subunits installed in series and having the shape and dimensions of 40-ft ISO-standard containers. All individual process stages (i.e. biotreatment steps) required for effective secondary treatment are smartly integrated in these container-like subunits.

The designed packaged biotreatment units make efficient use of two state-of-the-art wastewater treatment technologies, namely the MBBR-IFAS and the High-Rate Clarifier technologies.

‘GOUVES’. PACKAGED S.T.P - GENERAL ARRANGEMENT DRAWING

DEVISE ENGINEERING S.A. ENVIRONMENTAL TECHNOLOGIES

Head office: Factory address: 67 Aiolou Str, 10559 Thesi Mavri Ora,19300 Athens, Greece Aspropyrgos, Greece Tel. +30 210 3211040, +30 210 3222825, fax +30 210 3222012 Tel. +30 210 5596060 e-mail: info@devise.gr website: www.devise.gr

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The term MBBR-IFAS stands for Moving Bed BioReactor – Integrated Fixed Activated Sludge and refers to hybrid systems where both suspended and attached biomass is present in the same bioreactor. More specifically, the attached biomass develops as a thin biological layer (biofilm) on the “protected” surface area of specially engineered plastic media (biocarriers). The biocarriers are kept in constant motion within the bioreactor either by means of diffused coarse-bubble aeration (aerobic bioreactors) or submersible propeller mixers (anoxic bioreactors). Special screens or sieves are used to retain the biocarriers within the bioreactors.

Advantages of the MBBR-IFAS systems include the following (WEF, 2010):

Ability to phase-in additional capacity or improve performance by adding more media;

Additional biomass for treatment without increasing the solids loading on final clarifiers;

Higher-rate treatment processes possible, thus allowing greater treatment in a far smaller

footprint;

Improved settling characteristics (reduced SVIs);

Reduced sludge production;

Simultaneous nitrification and denitrification;

Improved recovery from process upsets.

For the Solids Separation stage of the Biomass, submerged Hollow-Fiber MBR modules installed in two separate tanks are used in a packaged form. DEVISE has used in this instance a compact design manufactured by KOCH – Puron PSH1500-40 type, providing a very compact design of high standards.

The innovative hybrid design of DEVISE ENGINEERING [UltraClear-BioPlant] combining MBBR-IFAS & MBR treatment methods has already proven itself in smaller application and gives an STP of even more Compact Design than a Conventional MBR Plants.

The advantages of the DEVISE “Ultra-Clear Bio-Plant” can be summarized as follows:

Very Compact Design, achieving higher capacities at given reactor volumes

High Effluent Quality suitable for re-use applications

Higher Energy efficiency than standard MBR systems due to lower MLSS concentration in

the biological reactors (6.0 -10.0 g/l)

Ultra Filtration Membrane Modules operating at standard MLSS conditions (8.0 – 12.0 g/l)

Fully automatic operation with remote monitoring and SCADA system

The Gouves STP biological treatment stage comprises of four lines each having the following distinct compartments:

Anoxic MBBR-IFAS cell for pre-denitrification;

First aerobic MBBR-IFAS cell for main BOD removal;

Second aerobic MBBR-IFAS cell for residual BOD removal;

DEVISE ENGINEERING S.A. ENVIRONMENTAL TECHNOLOGIES

Head office: Factory address: 67 Aiolou Str, 10559 Thesi Mavri Ora,19300 Athens, Greece Aspropyrgos, Greece Tel. +30 210 3211040, +30 210 3222825, fax +30 210 3222012 Tel. +30 210 5596060 e-mail: info@devise.gr website: www.devise.gr

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Third aerobic MBBR-IFAS cell for nitrification;

MBR cell for biomass separation;

Machine room for equipment and controls installation.

Finally, the excess sludge process line comprises the following:

A 185-m3 effective volume covered underground reinforced concrete rectangular tank for sludge collection and pre-thickening;

A sludge conditioning (i.e. flocculation) system containing a static mixer, an automatic polyelectrolyte solution preparation unit, and two diaphragm-type polyelectrolyte dosing pumps;

A centrifugal decanter for sludge dewatering up to 20%. Summary:

The “modular-packaged-high-quality effluent” STP design selected and implemented by DEVISE ENGINEERING SA for the Gouves STP project offers the following significant advantages:

Reduced footprint requirements compared to most conventional designs

Fully enclosed systems, bio-plants – pre-treatment plants, raw sewage tanks, sludge management, etc.

Ability to reliably deal with the seasonal hydraulic & waste load fluctuations typical problem in touristic areas

Easiness to increase capacity for future demands

Effluent quality for many re-use applications

Fast and cost effective project implementation

Easy to operate and maintain