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| History Capabilities |
Puerto Vallarta - Mexico
History - Puerto Vallarta is a major tourist resort located on Banderas Bay on Mexico's Pacific coast. The town's population has increased six-fold since the mid-1960's which resulted in the overloading of the original wastewater treatment facilities.
Further complications were due to major fluctuations in foreign residents and tourists which at any one time can be up to eighty thousand people. Additional sewage comes from ships berthed in the local port facilities which must also be treated.
The building of a new wastewater treatment plant has protected the environment, ensuring the bay and beaches remain pollution free. This has enabled Puerto Vallarta to develop into a major international holiday resort.
Finalised in 1993, the Puerto Vallarta scheme was the first sewage privatisation project awarded by the Mexican Government.
Puerto Vallarta Water Authority (SEAPAL-PV) initially commissioned Cascal to finance, design, construct, operate and maintain a new wastewater treatment facility for the city under a Build Own Operate and Transfer (BOOT) basis.
Finance was provided by the International Finance Corporation and the Mexican Bank of Public Works (Banobras) making Puerto Vallarta the first privately financed 'greenfield' site sewage treatment plant in the world. The scheme was structured and financed without any direct Government Guarantees.
In September 2004 the transfer of the infrastructure ownership from Cascal to SEAPAL took place and the original BOOT contract was terminated and a new Operations & Maintenance (O&M) contract was put in place.
The new O&M contract has virtually identical performance, obligations and duration as the BOOT contract. Cascal is still responsible for ensuring the effluent meets the required discharge standards which will continue to protect the excellent quality of bathing waters and the environment in Banderas Bay.
Capabilities of the Puerto Vallarta Wastewater Treatment Plant - Construction commenced in mid-1993 with commissioning in early 1995 and operations starting soon after.
The design of the new works was based on an original concept by SEAPAL-PV and was subject to detailed seismic analysis due to its location in an earthquake zone. A major ground improvement scheme was required due to the high water table and weak soil. Ground improvement was carried out with 3,800 stone columns, each 900 millimetres in diameter and eighteen metres deep.
The plant is designed to treat a maximum sewage flow rate of 65 Mld, which has never failed or exceeded the permissible limits. The plant is fed by a seventeen kilometres long rising main from the town. Full biological treatment which exceeds internationally recognised standards is provided, based on a conventional activated sludge process.
The site comprises a screening and grit removal plant, followed by an oxidation ditch, which uses horizontal shaft aerators. Final clarification is provided using circular settlement tanks, the excess sludge is aerobically digested and mechanically dewatered to twenty-one percent dry solids content so that it is suitable for landfill or agricultural purposes. The final effluent is chlorinated to ensure that the discharge from the plant meets the required bacteriological standards.
The effluent quality exceeds the environmental standards set by the Mexican Government and the World Bank.
