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Implementation process of PURE investment in Riga

When joining project PURE, Riga Water had identified three rapid measures to reduce the amount of phosphorus discharged to the Gulf of Riga from Daugavgriva wastewater treatment plant. These measures were to purchase and install

  • storage and dosing tanks for phosphorus precipitation chemical to improve the phosphorus removal efficiency;
  • magnetic flow meters to provide exact waste water flow measurements needed in steering of the process and
  • an additional sludge thickening centrifuge to achieve the necessary capacity for excess sludge removal and to prevent wash-outs of activated sludge.

Procurement and installation of the chemical dosing tank and flow meters

The first meeting of the procurement commission for purchase of phosphorus removal equipment for Daugavgrīva WWTP took place in summer 2010 and the open tender was launched on 13th August 2010 and published in www.iepirkumi.lv, Riga Water website and official newspaper Latvijas Vēstnesis. The tender consisted of two lots: one for ferrous sulphate dosing container and another for electromagnetic flow meter (2 pcs).

On 20th September 2010, in a meeting of the procurement commission, the proposals from three applicants (Ekomuovi Oy, SIA Inducont and Eccua OU) were opened. Two proposals for both lots were given. On 22th September, the winner of the tender was nominated: for LOT 1 – SIA Inducont and for LOT 2 – Ekomuovi Oy. On 11th October 2010 a contract with SIA Inducont was signed for supply of electromagnetic flow meters with a contract price of 28 100 EUR (without VAT). On 27th October 2010 a contract was signed with Ekomuovi Oy for supply ferrous sulfate dosage container with a contract price of 98 800 EUR (without VAT). Delivery of the equipment took place by the end of 2010.

The construction works agreement to install the equipment was concluded in November 2011 to be ready until March 2012. Due to winter conditions and corrections of the design, Riga Water Board decided to prolong the construction agreement until end of June 2012. The flow meters and the chemical storage were put into operation during spring 2012. The installation works were covered wholly by Riga Water’s own funds.


Installation works for flow meters. The inlet pipes underground had to be moved to make space for the flow meters. Photo: Riga Water.
Installation works for flow meters. The inlet pipes underground had to be moved to make space for the flow meters. Photo: Riga Water.



The ferric sulphate storage and dosing tank installed at Daugavgriva WWTP. Photo: Riga Water.
The ferric sulphate storage and dosing tank installed at Daugavgriva WWTP. Photo: Riga Water.

Procurement and installation of the decanter centrifuge for sludge thickening

Open tender process for the purchase of decanter centrifuge for WWTP Daugavgriva was launched on 23rd April 2010 (published on www.iepirkumi.lv, Riga Water website and official newspaper Latvijas Vēstnesis). Subsequently, the deadline for submission of the proposals was prolonged from 21st May to 4th June.

On 4th June 2010, in a meeting of the procurement commission, the proposals from three applicants were opened. On 9th 2010 June in the evaluation meeting of the procurement commission it was decided to 1) eliminate one tenderer (Huning Umwelttechnik GmbH) due to proposal’s non-compliance to the procurement regulation; 2) to ask other tenderers (Andritz Separation GmbH and SIA Alfa Laval) to give more accurate information on their proposals. The separate visits of two latter tenderers to the site of Daugavgriva WWTP were arranged, after which the procurement commission nominated Andritz Separation GmbH to be the winner of the tender. On 13th September a contract for the delivery of a decanter centrifuge was signed with Andritz Separation GmbH with a total contract price 234 994 EUR, equipment supply price - 146 500 EUR.

The implementation schedule of the centrifuge supply and installation was, however, delayed due to manufacturer’s problems. The supplier had unexpected technical problems regarding the gear box of the centrifuge and vibration of the manufactured equipment during several testing attempts. Riga Water’s experts visited the factory in Germany (Köln) in order to inspect the centrifuge manufacturing process and canceled the supply agreement with Andritz Separation due to malfunctions and unacceptably high vibrations on "ready to deliver" tests.

Riga Water prepared a new tender for centrifuge delivery and re-opened the tender in September 2011 and two offers were received on 29th of November 2011 – from GEA Westfalia Separator Group Gmbh and Alfa Laval Ltd.

On 24th April, an agreement for centrifuge delivery was concluded with GEA Westfalia Separator Group Gmbh (contract price 129 900 EUR without installation works). The centrifuge was delivered and installed in early autumn 2012. Installation costs are fully covered by Riga water own costs.

On the left the ferric sulphate storage, on the right dosing tank installed at Daugavgriva WWTP. Photo: Riga Water.
On the left the ferric sulphate storage, on the right dosing tank installed at Daugavgriva WWTP. Photo: Riga Water.

Future plans

The expected delivery of the other phosphorus precipitation chemical tank with funding separate from PURE took place in December 2012. Operational costs of the purchased equipment will be covered by Riga Water.

After completing the investments for enhanced phosphorus and nitrogen removal, Riga Water will concentrate on such topics as sludge in their work. A feasibility study for better sludge utilization (worth app. 25 000 EUR) is planned to be ordered by Riga Water. This is due to the fact that the costs (gasoline, land, contractors) of sludge handling are rising all the time. Waste-to-energy would be the preferred path: enhancing digestion in the tank or after it.

It has been agreed that Riga Water submits its yearly environmental report for EBRD to investment coordinator John Nurminen Foundation during the next 5 years to monitor the results of the project (http://www.puhdasitameri.fi/en).