Data Centre Water Treatment Principles
Introduction
Data Centres are critical to process and store our internet data. Up time is critical with 99.999% as a standard. For this, data servers which emit large amounts of heat need to be cooled and the cooling systems and water treatment systems need to be designed, operated and maintained up to a very high quality standard. Problems such as corrosion, scale, Legionella risk, and biofouling that come with water being used as a cooling medium, need to be managed intelligently.
Cooling Water Needs
Water is an extremely efficient and cost-effective medium for cooling data centres due to its high specific heat capacity compared to air. This means that water can absorb more heat without experiencing a significant temperature increase according to the formula Q = mC(Delta T). For instance, let’s consider the amount of water and air required to cool an 8kW server rack. While 3200 m3/hour of air would be needed, only 2 m3/hour of water would suffice, demonstrating the significant difference in heat transfer efficiency. However, water is a precious resource and it needs to be managed sustainably. This required indepth design and operational know how.
Bespoke Water Treatment Technologies Used
Depending on the source of water – which could be a bore hole, an open river (surface water), treated sewage effluent, sea water or least likely a potable water source – the water treatment technology differs. Also whether a wet evaporative cooling tower is used or a dry Air HEX (Heat Exchanger), the water quality requirements are different.
Bore holes in Slough, UK for example contain ferrous iron and if this is not removed, then the water turns red due to ferric oxide and all downstream filters get clogged.
Mains water in Holland is soft and there is no chlorine in it. So it is pointless to install a softener or an active carbon filter.
RO is normally used to demineralize the water and achieve higher cycles of concentration. But demin water is corrosive and special materials need to be used in the design of the pipes and equipment.
If treated sewage effluent is the available water source, then the design is completely different. Bacteria and TOC become the main culprits to worry about before subsequent water treatment steps.
If sea water is the medium for cooling, then corrosion resistant, expensive materials need to be used.
Experience of Kremesti Environmental Consulting Ltd.
Rami Elias Kremesti, MD of Kremesti Environmental Consulting Ltd, has worked on Data Centre projects in the UK and the EU. Managing water treatment for a data centre is very similar to managing the water treatment needs for the cooling systems of a power station which also has high standards for up-time and quality. Rami brings his ten years of experience on power stations to help clients to design water treatment systems for data centres.
Operational know how is also very critical because systems like Reverse Osmosis (RO) skids require careful operational monitoring and interventions when they become scaled or fouled or both.
Kremesti Environmental has designed training courses to help designers and operators of water treatment systems on data centres to achieve maximum efficiency and minimal downtime.
Figure 1.: Softeners, Active Carbon Filters, Ozone Dosing Systems, Reverse Osmosis Skid as part of a data centre water treatment project for a Dutch Data Centre
Environmental Impact
Data Centers are not environmentally friendly period despite all the green washing. They consume huge amounts of energy and large amounts of water for cooling.
Conclusion:
To maximise value for investment in a Data Centre project, an efficient water treatment design team is required to begin with. To minimise cost overruns, you need a consultant to over see the project. This is where Kremesti Environmental Consulting Ltd can help. After the system comes into operations, you need an expert water treatment operations team to keep things running smoothly.
Rami Elias Kremesti M.Sc., CSci, CEnv, CWEM