INDUSTRIAL WATER TREATMENT: SMART SAVINGS WITH SMART DIGITAL DOSING
In the northern region of India, water scarcity and poor water quality are significant challenges. Alleviating these problems is even more difficult in the Gujarat region where surface water and groundwater is limited while water quality is impaired by salinity levels above 2000 mg/l as TDS. Cities in the Gujarat region are experiencing a booming industrial sector, particularly in chemical, pharmaceutical and petrochemical industries. However, these industries are large consumers and polluters of water. And many borewells that were once providing clean water to local villages are now unable to produce water meeting drinking water quality standards or even water suitable for industrial processes. To address these water supply and quality issues, some industrial complexes in cities around Vadodara and Ahmedabad are implementing a range of water-saving solutions. In Vadodara, the Nandesari Industries Association (NIA) has developed their own desalination plant. Permionics, a pioneer of membrane technology and water treatment in India, has been responsible for the plant’s design, construction and current operation.
Permionics’ state-of-the-art desalination plant has a production capacity of 12 million litres per day (MLD) and is completely automatised, including SCADA and remote monitoring. The source of the polluted water is groundwater and surface water, as well as treated industrial and sewage wastewater, which is pumped from a combination of nearby sources. The water is equalised in an underground reservoir, where salinity varies between 2000-3000 mg/l as TDS. The water is then pumped into proprietary media filters (UFF Filtration) with automatic regeneration. The filtrate from the UFF filters is conveyed into another set of innovative design fine filters, and undergoes chemical pre-treatment with acid dosing to adjust the pH while antiscalants are added to prevent mineral scaling.
Chemical pre-treatment is an important step for the whole desalination process, helping the plant significantly increase efficiency and therefore produce less concentrate for further disposal. The chemically conditioned filtrate water is pumped through multistage pumps into a reverse osmosis (RO) membrane configuration of two stages to achieve optimum recovery. Permionics’ capability in membrane manufacturing, and tailoring membrane and system design, has been key to allowing borewell water and wastewater to be fed to the plant. The permeate water obtained from the RO membranes reaches a conductivity of less than 150 µS/cm, which is suitable for most industries present in the Vadodara complex. Ultra-pure water is also available if required.
Grundfos supplied all pumping equipment for the desalination plant, with product quality a decisive factor in supporting a future capacity increase of 5 MLD. The plant also became an innovative testing ground, enabling Grundfos to refine and develop its future offering. Grundfos implemented a Smart Filtration Suite: a set of innovative controls targeting membrane filtration, including desalination control. Smart RO provides significant operational savings in energy and chemicals. Its main features include a unified data normalisation analytic control, as well as an antiscalant controller and optimiser that can run in auto-mode.
The plant has been able to cut its antiscalant consumption by 75%. CIP frequency is also likely to be reduced substantially, leading to a saving in shutdown time, while at the same time maintaining membrane lifetime. A key driver of these achievements has been the Grundfos Smart Digital DDA – an advanced digital dosing pump. The pump can communicate via bus with the PLC and send set-point data. It can also detect chemical levels in the tank and communicate the status to the PLC for preventive actions. The quality of the water changes over time, even during a day, so the conductivity can vary by more than 1000 µS/cm. Inorganic content in the water is also a challenge.
Savings after benchmarking
The smart filtration controller in the dosing pump took care of defining the optimal set-point of antiscalant dosing in auto-mode instead of a fixed constant dosage. In addition, energy use in the high-pressure pumps was decreased when dosing at 1 L/h instead of 4 L/h.