Overview

From March 2014, Sterner were engaged by FAI to design various elements of the facility at Ardtoe. From the initial discussions on inlet treatment for the sea water intake, the brief expanded to include updated site distribution, water storage, disinfection for the site supply, and then the design of the trials unit facility. This building incorporates five identical rooms for challenge works up to Home Office approved standards, and has the capability to run sea or fresh water at a range of temperatures. The final part of the main design works was the design of the effluent treatment plant which disinfects the effluent from the trials facility such that it is safe to discharge back into the sea.

Our design team, working closely with the client, developed the concept design and fleshed out the available options for each section of the works. AutoCAD drawings, 3D presentations and process diagrams were all used to provide records and proposals of solutions.

The client’s requirements must be developed into a usable specification of inputs and outputs in order to propose solutions, so our team worked with the customer to discuss industry standards of treatment levels, modes of operation, even down to standard operating procedures for staff during the work.

From these discussions we were able to provide advice and options to the customer in order that the finished product was not only up to their needs, but up to their expectations.

Using our extensive network of suppliers, and calling on their expertise in their own fields we were able to ensure the correct equipment solutions were provided for each element of specialist supply. We were also able to fast track the solutions on site by specifying and ordering the equipment ahead of full design approval which in turn reduced lead times on equipment delivery.

Our scope of supply ranged from large bespoke items like the inlet drum filters, to specialist aquaria lighting, to a full monitoring and control system.

In addition to designing and equipment supply, one of our core strengths is to carry out installation and commissioning works. Our team of qualified engineers and electricians carry out the full range of electrical and mechanical installation and our technicians will carry out the commissioning of systems large and small. For this project we installed a range of pipework from 2” to 12”, in a range of materials, and carried out electrical installation not just for our equipment but for the building supplies for the trials unit including general lighting and power throughout.

Sea Water Inlet

The existing sea water supply to the site was through two existing self priming centrifugal pumps, which had been operating for several years on a manual changeout.
In order to secure the supply, two new pumps were proposed, with an automatic change over panel. The raw water would need filtered and then supplied to the site.
The existing system was using a pump to overflow method, so there was a constant energy use irrespective of water demand. We proposed a new control method incorporated into the treatment system which measured the water usage by the site and regulated the pump speed to only supply the water that was required at the time, thereby lowering energy costs. We also introduced a timed maintenance changeover and alarm functions on the pumps.

The first stage of the treatment system is a settlement tank which allows the settlement of larger suspended solids as raw sea water is being pumped into the system. The velocity of the water is reduced to allow vegetable matter to float to the surface and be caught in baffles, and suspended solids to settle out and be caught by baffles located in the lower section of the tank.

Two self cleaning drum filters were installed to deal with the full flow in a storm situation, filtering the water down to 30 micron. The filters have an automatic back wash facility, so are fully automated in terms of their cleaning and day to day operation.

The site is then supplied using two new booster pumps in a duty/standby arrangement to push the filtered sea water to the site.

Holding and Treatment

Previously the site was supplied directly from the sea water intake pumps, through a sand filter and directly to the point of use from a small header tank. This left the site susceptible to tidal influences on flows, and low retention time in the even of catastrophic power failure - a regular event given their remote location.

Header tanks

The site flow was directly in relation to the pumped supply from the SW intake pumps. The tidal variations on the inlet line gave rise to changes in suction head, and therefore the flow through the pumps could vary by up to 40%. To balance this out, and to provide security of supply in the vent of catastrophic power failure, we installed two 50m3 holding tanks. These tanks are capable of being used in tandem or isolated to allow dedicated supply to various parts of the site.

UV disinfection

After micro filtration pre header tank, the process water needs to be disinfected prior to use within the site and trials unit. There are two grades of disinfection, now for the stream that is dedicated to the trials unit, the other for the remainder of the site. Using feedback from the client we instigated doses that were relative to the point of use and potential pathogens.

Temperature manipulation

The trials unit facility was to be built to be as flexible as possible, and therefore four different temperature regimes were to be made available for use within the rooms. We designed and supplied a container into which were fitted controls and heat exchangers which, using energy from a biomass boiler, are capable of raising the temperature of the ambient flow through water into the high twenty degrees. A recent trial run within the unit had sea water at constant 30C for three weeks in November.

Distribution networks

For the delivery of water to the individual trials rooms, we designed, supplied and installed a container, prefabricated off site to house delivery pumps and controls. The lines are pressurised to ensure that at point of use within the rooms, a steady pressure is maintained irrespective of the settings at individual tanks. This allows simple day to day operations to be completed without the need to balance tanks within the room, or indeed within other rooms.

Trials Unit

The project started with a simple trials unit, however through various design changes and increments, we ended up with a six room facility, each housing it’s own biosecure stream, with seven tanks to allow Home Office approved works.

Infrastructure

The facility is remotely located form the distribution container, however, but choosing the correct pipework design the pressure losses are kept to a minimum. Externally pipework has been insulated to maintain the temperature of the flow, and internally, the pipework runs are reduce to a minimum. All key elements of control and maintenance are situated in the accessible roof space to allow engineers to access plant without having to access through the biosecure area.

Tank rooms

The facility was to be constructed such that it was a biosecure, full wash down area. We designed and installed the walls, ceilings and floors using food safe thermal panelling, and a sealed floor screed to allow easy cleaning in a non slip environment. Doors and glazing panels were installed, and a bio secure changing area for each room was created.

Monitoring

A centralised monitoring system, OxyGuard Commander, was installed to provide full monitoring and alarm capability on water quality, water treatment and all plant alarms. The system is equipped with multiple screen access points, local alarms, sms alarms, and provides full data point logging for up to 3 months.

Lighting

Each trials room was provided with specialist lighting to allow full light manipulation of the environment, with programmable dawn/dusk dimming, and variable day lengths.

Feeding

Each tank is provided with an automatic feeder, with a 5lt hopper affixed to the lid of the tank. The feeder controls are access from the main lab room, and the controller logs all feed, doses and times for record.

ETP

Effluent from the trials facility has the potential to contain contaminants, so in accordance with Home Office guidelines, the waste must be disinfected prior to discharge. Our design solution was to rely on our tried and tested methodology of filtration, ozone and UV. another key element in effluent filtration being the consideration of a failure event as this can have catastrophic impacts. So each step is provided with effective backup.

Filtration

The first stage in the process is to remove solid waste, this is done using a drum filter with a self cleaning function. Waste from the drum is collected in bag filters and is then removed by hand for incineration. There are two filters installed, one as a full standby in the event of an accidental overloading of the system, or some mechanical failure in the system.

Ozone

Post filtration the effluent is pumped through an ozone contact chamber. Ozone is an effective means of treatment for disinfection of pathogens and degrades naturally to harmless O2. We supplied and installed a self contained unit which consists of an oxygen generator, ozone generator, and pressure system to provide a suitable dose. effective monitoring of REDOX levels allows the system to be self regulating dependant on the demand on the system.

UV disinfection

As a fail safe, a full UV disinfection system is included in the even of a failure within the ozone generation system. The dosing of 4000 J/m2 is sufficient to ensure a disinfection rate which would prevent escape of any pathogen. UV is also an effective means of reducing residual ozone in the water, and therefore serves a dual purpose of enhancing the ozone system and providing the back up in the even of a failure.

General principles

The design of the systems should be led by the customer’s end requirements, and our job is to identify those requirements and propose effective solutions. These solutions will initially be transmitted in the form of process diagrams to agree basic principles, and then expanded into full spatial designs with 3D drawings of critical parts in order to explain the equipment and operations.

Automation

We believe firmly that the systems should react to the user, and not the other way around. If a user opens a valve on one tank the system should immediately react and compensate such that no other tanks are affected. In this project, the opening of a 1” valve in one of the trials rooms will make the distribution pump run faster to give more water, the heating pumps and controls operate to ensure the temperature is maintained, and the site supply pumps ramp up to ensure the header tank is kept at the same level.

Security

We also ensure that fail safes are given high priority - each pump should have a standby pump with an automatic change over in even of a pump failure, key water levels should be monitored and alarmed to give early warning of impending problems. Any automated parts should file safe such that gravity can still ensure water supply to the biomass.

Using a variety of sensors, actuated valves, alarms, telemetry and monitoring solutions we can effectively log multiple parameters and identify trends in the system useage. Using this data and trend analysis early warning alarms can be set up to trigger not only emergency responses but planned maintenance to ensure proper working of the equipment.

Containerised solutions

Sterner have delivered several projects where offsite manufacturing has been key to a successful delivery. In this case we used combinations of 10’ and 20’ containers, fully lined and insulated to provide “plant rooms” for pumps, controls, heat exchangers etc.

The containers and equipment were built in our facility in Inverness and then shipped to site for installation. This method has the advantage of providing a more flexible solution to location of plant, reduces the install time on site, and allows the construction of key equipment and controls within a controlled environment rather than a remote location.