water technology

For one water treatment supplier, 2008 turning out to be a very busy year, despite the downbeat economic forecasts.

Siemens Water Technology (SWT) has won a number of significant water treatment contracts in the US, including one large technology licensing deal.

The licensing agreement is with CSO Technik to supply and service the Crown sludge disintegration system in the US, Canada, and Mexico. The US patented cell lysing process eliminates digester foaming, increases gas production by up to 30 per cent and reduces solids for disposal by 20 per cent.

The Crown system complements Siemens’ Dystor dual-membrane gas holder system that captures biogas produced by the anaerobic process. The Crown agreement will round out Siemens’ anaerobic digestion product portfolio, making it a leader in the municipal biogas market in North America.

The Crown disintegration system is installed after the sludge thickeners but before the digester. Sludge is first fed into the system’s recirculation tank. It then goes through a homogeniser. The uniform mixture is then pressurised to 175 psi and pumped through a high-speed mixer and into the disintegrator.

As the pressure is relieved, the biosolids cells rupture and release endo- and exo-enzymes and destroy filament-building micro-organisms. The disintegrated sludge is then sent back to the recirculation tank, where the process is repeated before being discharged into the digester.

The Crown system partners with Siemens’ Dystor dual-membrane gas holder system, which maximises gas storage through its geometric shape. The latter’s many operational advantages makes the Crown – Dystor synergy a combination unequalled in the industry, says the company.

The Crown sludge disintegration technology is ideal for a variety of municipal wastewater treatment applications. Existing customers with co-generation facilities can pair the unit with Siemens’ Dystor gas holder system to maximise system potential through increased gas production and storage. The system can also prove beneficial for customers that live in areas with green energy or self-generation tax incentives as well as for municipalities that have other high-volume biogas end-users.

Compared to a competitive physical/chemical cell lysing process, the small footprint Crown process consumes less energy and greatly reduces chemical, equipment, and sludge hauling costs. Pre-fabricated and containerised for fast installation, the Crown process is adaptable to variable loads and improves sludge dewaterability and digester stability. The system also uses equipment that is common to most wastewater treatment plants. The Crown disintegration process is already operational at several wastewater treatment plants worldwide.

A second deal involves a contract to provide secondary clarification systems for the Metro Wastewater Reclamation District’s (MWRD) North Secondary treatment complex improvements project in Denver. The plant upgrade will include twelve 130-foot diameter Tow-Bro clarifier mechanisms for secondary treatment.

The new clarifiers will improve performance over the existing organ pipe type clarifiers – specifically, improved energy dissipation and velocity profile control, improved flocculation, and even sludge withdrawal, particularly important under poor solids settling conditions. The project is scheduled for completion in 2012.

The Robert W Hite Treatment Facility serves a population of approximately 1.6 million in the metropolitan Denver area. Improvements to the North Secondary treatment complex were needed to replace aging clarifier equipment, increase solids and hydraulic loading capacity, and improve overall treatment performance.

The District worked with Carollo Engineers, HydroSims and CPE Services using plant specific settling analysis, computational fluid dynamic (CFD) modelling, and full scale stress testing to determine the best solution to meet the plant’s final clarification requirements. The engineering firm recommended the Tow-Bro clarifier mechanism.

The advantages of the Tow-Bro unit include uniform sludge removal from the secondary clarifier under a wider variety of flow, solids loading, and sludge settling conditions. These advantages provide greater solids and hydraulic loading capacity when compared to the existing hydraulic-removal-type clarifiers. The clarifier design utilises a centre-feed configuration with peripheral effluent launders. Flow enters the clarifier through a specially designed maze type energy dissipating inlet (EDI). The specific configuration of the maze EDI was designed with the assistance of CFD modelling to determine optimal dimensions.

After initial energy dissipation, solids are flocculated and settle to the tank floor where they are removed uniformly by the Tow-Bro unitube header. Concentrated settled sludge is returned to the aeration basin from the clarifier. Clarified effluent flows into an inboard launder and exits the tank. Scum is removed via a ducking skimmer assembly. The treated water then flows to the Metro District’s disinfection facilities for further treatment prior to discharge into the South Platte River.

The new clarifier mechanisms will be installed in multiple phases over the next three years. To minimise the impact of construction on plant capacity, Garney Construction of Littleton, Colorado, will replace three of the 12 clarifiers at a time. The existing clarifiers will remain online until they are replaced with the new Tow-Bro mechanisms.

A third contract is for the delivery of five IPS composting system agitators to the Burlington County, New Jersey Board of chosen freeholders, as part of an upgrade to the county’s ten-year-old composting plant.

The plant supports the county’s biosolids composting and beneficial use programme for 14 municipal wastewater treatment plants.

The new IPS equipment will replace the plant’s existing ten-year-old Siemens’ composting agitators. Two agitators will be delivered this year, with the other three installed in early 2009. This schedule will allow the capital cost to be spread out for two fiscal years, and the entire order delivered within the shortest time frame so as not to impede plant operations.

The IPS composting system is an enclosed in-vessel, agitated, aerated, automated composting process with biofiltration odor control. It transforms dewatered biosolids, municipal solid waste and source-separated organics (SSOs) into high-quality compost products. The system also stabilises residual waste in mechanical biological treatment.

At Burlington County, Siemens conducted on-site composting system studies to help determine the best plan for implementing the upgrade while meeting the county’s budget. The company also worked with its suppliers to meet the challenge of a relatively tight timeline. The new IPS equipment will allow the county to continue its success managing biosolids from the wastewater treatment plants, thus providing beneficial use of the compost product and reducing greenhouse gases to the environment.

SWT also announced in August that it is to provide Meriden in Connecticut with second supervisory control and data acquisition (SCADA) system, valued at US$1.3 million.

The city’s latest system, to be installed as part of an upgrade at its 11.6 million gallons/day water pollution control facility, will be compatible with the SCADA system supplied by Siemens to Meriden’s water division facilities in 2002.

Once the new SCADA system comes online in early 2010, it will allow the city to control and monitor 1550 process-related database points, make informed decisions regarding the operation of the pollution control facility, and optimise process operations. This, in turn, will improve the facility’s effluent.

Siemens’ scope of supply includes SCADA system hardware and software application engineering, facility-wide instrumentation and controls loop drawing documentation, and project management coordination. SCADA system factory staging and testing will be included as part of the contract, as well as a formal customer/city factory witness test.

Field service support will include onsite installation supervision, field readiness testing, system start-up and commissioning and a formal customer/city test for final SCADA system acceptance. Siemens will also provide Meriden’s operations and maintenance personnel with onsite formal training in the use, maintenance and troubleshooting of the pollution control facility’s new SCADA system.