Why is it, that in developed countries we have changed our behaviour and now routinely sort and recycle our solid waste, yet we still deal with our liquid waste the same way we have done for the last few hundred years?

Before we go any further, I should clarify a term used herein. Most people talk about ‘wastewater’, in this article we will refer to this as ‘used’ water.

Advances in technology mean that these days it is quite easy to recycle used water for non-potable reuse, and recover some of the energy we pump into the creation of hot water. The costs of these recycling and energy recovery systems are steadily coming down, while the reliability and rewards (both financial & environmental) are steadily growing.

We do however need to change the way we think about used water. It’s not filthy, dangerous stuff. It’s low mileage water, with one careful previous owner, who has pimped it up a bit with the addition of some fertilizer and energy. Surely that sounds too good to throw it all away don’t you think?

Risks & Rewards
Of course used water can contain bugs, bacteria and viruses that can make people sick. Main electricity can make you feel quite unwell if you grab the end of a live cable or stick your fingers in a socket. Just as we do with our electricity, we simply need to manage the associated risk with recycled water.

Risk management strategies for recycled water schemes include things like:

• Where possible (e.g. in new buildings where the plumbing systems can be easily configured), use only grey water as the source for the recycled water. The potential health risk if something goes wrong is then reduced considerably right at the start.
• Design the water treatment system so it produces recycled water which is safe for the intended use, and safe for the people who might reasonably be expected to come into contact with the water.
• Make sure people know where recycled water is being used, by using coloured pipes to differentiate the contents from potable water, and ‘Recycled Water’ signage at outlets.

The list above provides just a few examples of risk management, as there are many other possibilities. There are equally many International, National and Regional standards and guidelines to assist designers in coming up with appropriate risk management strategies for any water recycling scheme.

Apart from the obvious environmental benefits of using less water and less energy, other rewards for implementing these types of systems can include:

• In a water starved region, it might make the difference between the project going ahead or not, or perhaps enable the construction of a larger building than is otherwise possible.
• Creating recycled water using a single Membrane Bioreactor (MBR) system could allow a building to qualify for all of the 5 possible Water Efficiency points under LEED v2.2.
• Water is a much better conductor of energy than air. Recovering heat from used water with heat pumps creates heating/cooling energy at Coefficients Of Performance (COP) around 5 – 6. This means that for every 1kW of electricity consumed by the heat pump, you are getting 5kW – 6kW of useful heating (or cooling).

Technical Issues
It is not my intention to go into deep technical detail here about the inner workings of treatment systems. For most people, this technical stuff makes your eyes glaze over and I know that your reading of this article can be terminated at any time with a simple mouse click. I want you to stay with me until the end, so I will keep the technical part simple and brief.

Those of us in the used water industry know very well that people dispatch all sorts of goodies down their drain pipes. How some of these things get there, the Lord only knows! Nevertheless, there they are and we must deal with them.

Most of the problems that water recycling systems and energy recovery systems suffer from are caused by fouling from hairs, fibres and coarse solids. These problems present themselves in the form of blocked membranes, clogged air diffusers and blocked heat exchangers.

When collecting used water, inevitably sludge settles out and accumulates over time. The equipment must operate with this and there must be a plan to deal with it.

Solutions
The solutions described here are just a taste of what is available, and what we offer in our business. Our speciality is wastewater....oops I mean used water, and so we offer solutions specifically designed to operate in this environment.

• Grey water Recycling is relatively straightforward. The water is only slightly ‘pimped up’, and so treating it for recycling is quite simple with coarse pre-screening and MBR ultra filtration.  We have a system in our company, called the GreyUse system, which applies to this.
• Black water Recycling requires more care since we must deal with more pollutants and the system design must be more resilient (assuming that there is no connection to a reticulated sewer system) as system failure can lead to very undesirable overflows of raw used water. In these applications we again provide coarse pre-screening and use MBR ultra filtration, but we do our own pimping up of the system by adding things like additional aeration, UV or chlorine disinfection, extra controls, maybe duty & standby pumps or throw in a grease trap etc. We have a range of systems for Black water applications, and the most appropriate solution and what extra requirements are needed, is assessed on a case-by-case basis.
• Energy Recovery from used water we do in two forms. One is ‘sewer mining’ whereby we can make small connections into a large trunk sewer and tap the used water flowing past. The other consists of simply tapping the used water generated in a building before it is discharged to a sewer. In both cases we do coarse pre-screening of the used water, and then run the used water through one of our RoWin heat exchangers. These heat exchangers have been designed and developed specifically for used water and feature robust Stainless Steel construction, large diameter tubes with fully automatic cleaning wipers, absence of small fluid pathways (since these are easily blocked) and a sloping base with sludge removal screw to remove sludge build up. To our knowledge this is the only heat exchanger on the market with these features.

Case Studies
At last count HUBER has participated in almost 800 water treatment projects producing water suitable for recycling. These projects are in locations spanning the globe. They range from small systems for a single house to large municipal used water schemes, and can be found in cold or hot climates, easy new builds, and difficult retrofits. The case studies presented here have been selected to illustrate a range of sizes and applications. Due to space constraints, I have kept the descriptions brief.

Los Cabos Hotel & Resort - Baja California, Mexico. Black Water Treatment with Treated Water Recycled for Irrigation. The Pueblo Bonito Sunset Beach Hotel is a 5 star hotel and resort located in Los Cabos on the Southern Tip of the Baja Peninsula. The Hotel & Resort offers: 327 bedroom suites, 7 on site restaurants & bars, 650m² of conference or meeting room space, on site fitness studio & beauty spa, 10 swimming pools. The hotel is operated by Pueblo Bonito Oceanfront Resorts & Spas. For this project, HUBER designed, supplied, installed and commissioned a 130m³/day Membrane Bioreactor (MBR) ultra filtration system to treat the combined black and grey wastewater. The treated water is recycled for irrigation.

Romanos Hotel – Greece. Black Water Treatment with Treated Water Recycled For Irrigation. The Romanos Costa Navarino is a 5 star hotel offering: 321 luxurious rooms and suites, including 121 with individual infinity pools, Approximately 10 restaurants & bars on site, Open air cinema & Various retail outlets. The hotel was opened in 2010 and is operated by Starwood Hotels under their 'Luxury Collection' brand. Costa Navarino has put a strong emphasis on environmental responsibility. All properties being developed in the destination must meet strict environmental standards in order to protect the landscape for future generations. For this project, HUBER designed, supplied, installed and commissioned a 1000m³/day Membrane Bioreactor (MBR) ultra filtration system to treat the combined black and grey wastewater. The treated water is recycled for irrigation of the adjacent golf course.

Plaza Indonesia Shopping Mall - Jakarta, Indonesia. Black Water Treatment with Treated Water used for Roof Garden Irrigation & Cooling Tower Make up. Plaza Indonesia is located in the centre of Jakarta’s central business district. Since its expansion in 2008, the mall now provides around 70,000m² of retail area over 4 levels. There are over 250 retail units, food outlets and other typical retail mall services. The site also includes the Grand Hyatt Jakarta, which provides 450 hotel rooms and suites, 7 on-site restaurants & bars, 14 conference/meeting spaces. This project presented some unique challenges for the HUBER team. The new wastewater treatment system had to be installed into the basement of the mall to replace the previous system; hence access for the machinery was severely limited. HUBER designed, supplied, installed and commissioned a 2,200 m³/day Membrane Bioreactor (MBR) ultra filtration system to treat the combined black and grey wastewater. This is compared to the 1,000 m³/d capacity of the original plant, which utilised the same space! The treated water is recycled as make-up water for the air conditioning cooling towers.

Small Office Building – Dubai. Black Water Treatment with Treated Water Recycled for Water Feature & Irrigation. This office building was built as a sales office for a Dubai based property development company. The building was completed in 2008 and provides office space for forty company employees over two levels. For this project, HUBER designed, supplied, installed and commissioned a 6m³/day Membrane Bioreactor (MBR) ultrafiltration system to treat the combined black and grey wastewater. The treated water is recycled for use in the water feature at the front of the building, and for irrigation.

Highrise Office Building - Winterthur, Switzerland. Energy Recovery from Wastewater.
The city of Winterthur is in Northern Switzerland. The Wintower building stands 99m high, has 28 floors of office accommodation and a penthouse apartment on the top. For this project, HUBER designed, supplied, installed and commissioned a sewer mining system, which yields 440kW of heating, respectively of cooling. The system operates with a Coefficient of Performance (COP) of approximately 5-6.

Alpine Hut -  Austria. Black Water Treatment with Treated Water Discharged Into Sensitive Environment. Olperer Hutte is an alpine lodge located in Zillertal region of the Tyrol Alps in Austria. It sits at an altitude of 2398m and access is only via foot or helicopter. The lodge was completely rebuilt in 2006 and today receives approximately 15,000 visitors per summer season, providing 66 beds and a restaurant. For this project, HUBER designed, supplied, installed and commissioned a 16 m³/day Membrane Bioreactor (MBR) ultra filtration system to treat the combined black and grey wastewater. The treated water is then discharged into the pristine alpine environment.