Going with the flow, digitally

A large energy supplier in the USA is employing Veolia Water Technologies’ AQUAVISTA(TM) digital services for supervision, control and operation of a flue gas desulphurisation wastewater treatment plant.

AQUAVISTA(TM) is Veolia Water Technologies’ cloud-based digital services platform and it will be customised and configured specifically for the treatment of wastewater at the power plant, providing an extra layer of support for Veolia’s operators.

A few years ago, Veolia Water Technologies was awarded the contract to supply its proprietary brine concentrator and CoLD® crystalliser to treat flue gas desulphurisation wastewater generated by the plant. The goal is Zero Liquid Discharge (ZLD) – with the recovered wastewater to be reused within the power plant – and closure of coal ash slurry storage ponds.

Veolia is going to operate and maintain the wastewater treatment plant in the coming years. The implementation of AQUAVISTA(TM) will provide the plant with digital monitoring and performance optimisation, improving asset performance, ensuring higher plant efficiency, including reduced chemical use, and making use of predictive analytics.

The CoLD® process

The CoLD® process provides crystallisation of high solubility salts at low temperature and deep vacuum and is essentially a conventional forced circulation crystalliser fitted with a vacuum system. It is a proprietary crystallisation process developed by Veolia to be more robust and simple than conventional thermal processes, with better economics.

The energy for evaporation can be provided by steam, and the low temperature sink can be provided by chilled water. The low operating temperature lowers the solubility of the high solubility dissolved salts, so they crystallise at a lower concentration.

The CoLD® process requires no chemical treatment of the wastewater and generates no additional sludge for disposal, thereby reducing operating costs significantly. It is an ideal solution to address stricter water reuse standards, mandated ZLD, and increasing regulation of discharge limits of total dissolved solids (TDS).

Conventional thermal processes for FGD (and IGCC) waste streams require clarification and extensive pre-treatment of the wastewater with lime, soda ash, caustic, and other chemicals to replace the calcium, magnesium, and ammonium ions in the wastewater with sodium ions in order to produce a crystalline solid to achieve ZLD.

In some cases, a final drying step is necessary to produce a stable solid suitable for disposal. Pre-treatment equipment includes chemical feed/storage facilities, solids settling or filtration equipment, and sludge dewatering equipment. These additional facilities increase the footprint of the ZLD system as well as the capital costs and overall maintenance. The logistics of unloading, storing, and preparing chemicals and dewatering and transporting sludge for disposal substantially increase the OPEX.

The CoLD® process, as noted, however, operates at low temperature and the chemistries of FGD (and IGCC) wastewaters favour the formation of many hydrates and double salts that precipitate at low concentrations as the temperature of the solution is lowered. When concentrating the waste stream at low temperature, dissolved solids crystallise at relatively low concentrations, without the need for chemical pretreatment and resulting sludge production. 

AQUAVISTA(TM)

The AQUAVISTA(TM) digital suite of standard and customisable water process management applications provides a rich, flexible intelligence layer that analyses, measures and benchmarks plant, process and equipment data for a whole range of functions, including: advanced analytics and diagnostics; condition monitoring; integrated asset management and benchmarking; optimisation of preventative maintenance; ensuring regulatory compliance; and interactive troubleshooting.

The information is supplied in real time and historically to authorised plant personnel across Veolia’s secure, private and user-friendly cloud-based web portal, which can be accessed remotely and on any device.

This secure, 24/7 managed service simplifies and facilitates plant management providing: real-time remote monitoring of equipment data; dynamic alarm management and information for operators; key information about service contracts and reports; archive of all service and sales orders; access to equipment data, such as user guides, performance documents, calibration certificates, documentation for a specific site, O&M manuals and training videos and materials for operation of selected technologies; notification of events.

The maintenance module in AQUAVISTA(TM) informs operators as to which maintenance tasks have to be done, when, where and how, integrating a checklist with maintenance tasks sorted by priority and performance KPIs to track maintenance performance.

In addition, the operator receives regular notifications enabling pro-active decisions to be made to improve performance.

Addressing the need for stringent cybersecurity measures to be integrated into the system, all physical security (data acquisition), network security (data transfer) and digital security (data aggregation / analysis) are embedded in the core of the platform design.