An Introduction to Basic Water Treatment Protocols for Pinnipeds Exhibits

John D Dineley

Presented at Whipsnade Wild Animal Park as part the Association of British Wild Animal Keepers Symposium '98.

INTRODUCTION

Pinnipeds are aquatic mammals and as such require access to a body of water as part of their captive environment. These environments are in turn subject pollution and protocols have to be implemented control contamination and ensure toxic chemicals and possible pathogens (disease causing organisms) are kept in check. This paper is a basic review of the water treatment technologies available and their application. It should be pointed out that in the interest of brevity some details on water quality have been omitted and I would refer readers to the reference section for publications containing more complete informing such as Spotte's (1993) excellent introduction to marine aquaria keeping.

The prime objective of any water treatment programme is to maintain a body of water in a pollution free state by continuous dilution. One of the most important consideration to achieve this when designing a water treatment system is turn-over rate. Turn-over rate is the amount of time it takes for a treatment system to pass the volume of a pool through it's system once, for example a system that services a pool of 100, 000 gallons of water at the flow rate of 50,000 gallons is maintaining a turn-over rate of two hours.

As regards the treatment system to achieve this gaol, one of the simplest solutions is the pumping of water from a natural source (e.g. the sea) through the exhibit and out to waste or by the construction of the exhibit as a sea-pen or fenced off lagoon. Unfortunately, such facilities have to be located in coastal areas and, moreover, such locations have to themselves free of pollution.

Therefore, unless a holding facility is in the fortunate position of being able to be at a location that allows the continuous addition and discharge of a safe, clean source of sea water into its pool(s) some form of water treatment system has to be operated. These fall into various different types that are detailed below.


BASIC MECHICAL FILTRATION

Mechanical filtration in the water treatment system is designed to primarily remove particulate matter; the most commonly used being sand pressure filters. These consist of closed vessel(s) containing a body of sand held above a supporting under drain assembly. Water is normally pumped into the vessel passing through the sand which strains and retains particulate matter. As the sand becomes clogged a rise in pressure across the filter bed can be noted. When the manufactures prescribed level for cleaning the filter bed has be reached, the filter flow is reversed and the dirt and water used for the cleaning operation is diverted to waste; compressed air is sometimes used to "fluidize" the filter bed during the back wash cycle to ensure total cleaning (Finlay, 1979). Once the water washing the filter bed appears to run clean the system flow is returned to normal and continues to filter the pool's water.

Most commercial systems designed for public swimming pools or public water supplies can be suitably applied to pinniped facilities. Many are now designed in fibre-glass that give them extended use in salt water applications.

Filteration aids are sometime added to sand filters such as the chemical aluminium sulphate. This chemical aids the precipitating (coagulating together) of small particles within the water making it easier for them to be trapped by the filter bed. However, as with any chemical addition testing and control is import as its accumulation within the pool water can cause eye and mucus membrane irritation. Levels should not exceed 0.3 mg/L (Anderson, 1973; Squires, 1977).


CHEMICAL CONTROL OF ORGANIC POLLUTION

Once water has been mechanically treated for the removal of particulate matter organic pollutants and the control of micro-organisms is undertaken in a combination of methods that may utilise both chemical and biological techniques.

Chlorine

Chlorine has been used in public water treatment since the beginning of the current century. In recent times it, along with many other chemicals, has received closer inspection as to it's threats to the environment. However, its beneficial utilisation in ensuring safe water for public consumption and recreation must be balanced against the above concerns. As regards pinnipeds, chlorination has been used successfully and safely for many years. However its inappropriate application in inexperienced hands can cause problems.

The chlorination of water is a complex affair and therefore a brief and simple technical explanation of its action in water may be helpful in understanding the process and avoid common application problems. The use of chlorine in the management of a pinniped exhibit has a two-fold purpose: to disinfect the water to reduce the likely-hood of the presence of pathogens and the oxidation of organic matter produced by the animals.

Chlorine (Cl) is an elemental gas and a member of the halogen family. However, it is rarely supplied in its gaseous form, which can be very dangerous if mishandled. It is mainly supplied dissolved in a liquid called sodium hypochlorite; this contains approximately 10 to 15 per cent of available chlorine. Moreover, chlorine can also be produced in salt water pools in-situ by electrolytic cells (Wallis, 1973; Squires, 1977).

When chlorine is added to pure water it is found predominantly as free available chlorine. This so called free chlorine is non-toxic at high levels and inactivates pathogenic agents within a short space of time. However, this situation is complicated when it involves water containing organic matter - particularly ammonia (NH3) - as a number of chlorine related compounds called chloramines can be formed. Although chloramines are available to kill pathogens they do so at a much slower rate than free chlorine. They are also responsible for causing eye irritation in humans and other mammals. The species distribution of chloramines, and thus the degrees of mucus membrane and eye irritation, are pH dependant; water adjusted to a pH of sea-water (7.8 - 8.4) will have a predominance of monocholramine (NH2Cl).

Fortunately, early research in chlorination techniques found that by continuing to add chlorine to waters containing these compounds resulted in a second chemical reaction. This second reaction, sometimes referred to as "break-point", effectively broke down the trouble-some chloramines and resulted in a predominance the non-toxic free chlorine thus resolving irritation problems.

However, for this process to take place safely in a marine mammal pool it has been demonstrated that there has to a minimum animal-to-water ratio. If there is not, the level of chloramines will reach a point where animals can be injured and burnt (Dineley, 1990). Anderson (1973), suggests that, as a rule-of-thumb, 100 cubic meters of water (approximately 22,000 gallons) is optimal for two harbour porpoises (Phocoena phcoena); one bottle-nose dolphin (Tursiops truncatus) or 1/10 of a orca or killer whale (Orcinus orca).

Research by Squires (1977), of the international oceanaria design and water engineering group Binnie and Partners, consider a minimum 0.5 kilogram body weight per cubic meter of water for seals, and that a level of free chlorine of up to 0.7 parts per million with chloramines residuals of less than 0.4 parts per million are the most suitable for pinnipeds; their research suggests that pinnipeds have much lower tolerance to chloramines than cetaceans. He further recommends the 10% removal and replacement of pool water per day and a pool water turn-over of 1 to 1 1/2 hours. Anderson (1973) states that ratios between free chlorine and chloramines residuals (combined chlorine) should be 2:1 or better 3:1.

Ozone

Ozone is a form of oxygen (O3) which is very reactive in it's ability to oxidise organic material (Palin, 1979). It is very unstable and has to be produced on site; it is generally mixed with treated water in a special reaction chamber before the water is returned to the pool. It is important that all ozone is removed before the treated water returns to the pool as it can be very noxious and dangerous.

It has many advantages including a high potential to kill both bacteria and virus, and has the bonus of producing water with a high clarity that may exclude the need to use coagulation chemicals such as aluminium sulphate (see below).

However ozone has two disadvantages:

• because of its volatile nature, it does not leave any form of disinfectant residual in the pool water. This can lead to uncontrolled algae and bacteria growth on pool surfaces;

• it is unable to convert organic matter from the ammonia stage in the water conditions (pH levels) found in marine animal pools (de Graaf, 1973).

Nevertheless, these problems can be resolved by using ozone in tandem with chlorination as ozone will breakdown ammonia once the chlorination process has combined with this chemical to formed chloramines (Palin, 1979). Chlorination will also allow the benefit of in pool residuals to control bacteria and algae growths. Ozone's high effectiveness at oxidising organic matter also allows a lower concentration of total chlorine residuals.

Geraci (1992) suggests that in totally closed circuit water systems he is in favour of the use of ozone sterilisation, rather than exclusive reliance on chlorination. He believes that although more expensive, it is more effective and safer for the animals.

Biological

The use of some form of biological control of organic pollution within aquatic mammal pools has been a relatively new development which in part have grown from the popularity of large public aquariums and mixed mammal/fish exhibits (van der Toorn, 1987; Dineley, 1990; IAT, 1996.).

The principles involved are the deliberate culturing of species of aerobic bacteria known for their ability to convert ammonia to nitrite (Nitrosomonas sp.) and nitrite to the nitrate (Nitrobacter sp.). The process is termed nitrification and is normally achieved in chambers sited after particulate filtration which containing media such as stones or plastic shapes that offer a large surface area for the bacteria to grow on.

The conversion of the remaining nitrate to atmospheric nitrogen is also possible but this requires anaerobic bacterial conversion. This processes is term de-nitrification. However, the process is slightly more complicated than nitrification with the bacteria cultural being maintained in an oxygen free reaction chamber or substrate (e.g. sintered glass) where they are forced to acquire their oxygen from the three of oxygen atoms contained on the on the nitrate ion.

Complementary to these biological systems is the use of the "protein" skimmer or foam fractionation and ultra violet (UV) light disinfection (1).

Foam fractionation usual takes place prior to the biological system and is design to generate a foam that can be removed from the system to waste; the bubbles within the generated foam contain dissolved organics that are attracted by the air/water interface of the bubbles. The foam generators on these systems can also incorporate ozone that increases the oxidation of organic population.

UV light disaffection is also incorporated into biological systems: UV-C lamps produce radiation that is damaging to all forms of life by the disruption of a cell DNA bonding (2). The process takes place in sealed chamber containing an array of UV light tubes that the treated water passes around. The UV tubes are protected by quartz sleeves as glass is opaque to UV-C radiation. An important point to note of UV-C tubes is that they only have an effective operating life of six-months.


WATER CHANGES.

One final point that is always important to bear in mind when operating the various water treatment systems outlined above and this is an assumption that water treated within such above systems do not require any periodic water replacement. Unfortunately, this is a fallacy that needs to be addressed.

Spotte (1993) makes the following point regarding the need for partial periodic water replacement in aquaria. He states that it remains a myth that current water treatment devices eliminate the need to periodically renewal of water in closed aquaria and that no experimental evidence has been undertaken to demonstrate the efficiency of many of the current technologies (ozone, form fractionation, etc.) in maintaining a closed body of water in a steady state indefinitely. He maintains that no systems currently exist that totally frees a closed circuit system from the many complex biochemical changes that take place, due to the metabolism of the animals within that environment, which does not obligate periodic water disposal and replacement. This indeed remains the current situation and it advisable the exhibits do undertake periodic partial water changes.

Unfortunately parameters for such changes are not clear and advised ranges can be from 0.5 to 10 per cent per day (Lee, 1993; Squire, 1977). Therefore, the most effective and convenient parameter may be monitoring the levels of nitrate (NO3) contained within the system and maintaining it at below 50mg/L. This is particularly important in a system using a biological water treatment system as elevated levels of nitrate and phosphate can cause enrichment of the exhibit waters with nutrients that cause rapid algae growth.

Suggested water quality parameters for pinnipeds (Squires, 1977)

References.

Anderson, M. (1973). Treatment of water in dolphinaria. Aquatic Mammals. Volume 1, Number 3.

de Graaf, F. (1973). Marine fish guide. Harrison, N.J. USA: The Pet Library Ltd.

Dineley, J.D. (1990). Principles of water treatment in aquatic mammal pools. International Zoo News. Volume 37/7, Number 224.

Finlay, W.S. (1979). Water treatment technology. London: Her Majesty's Stationery Office.

Geraci, J.R. (1992). Personal Communication. University of Guelph, Canada.

Intensive Aquaculture Technology Ltd. (1996). London Aquarium: Life support operation and maintenance manual. Barrow-on-Humber: Intensive Aquaculture Technology Ltd

Palin, A.T. (1979). Disinfection and stabilisation in water treatment technology. London: Her Majesty's Stationery Office.

Spotte, S. (1993). Marine aquarium keeping. New York: John Wiley and Sons, Inc.

Squires, R.C. (1977). Oceanaria water for mammals and fish. Journal of Water and Engineering Scientists.

Van der Toorn, J.D. (1987). A biological approach to dolphinarium water purification. Aquatic Mammals. Volume 13, Number 3

Wallis, A.P.L. The maintenance of satisfactory water conditions in dolphinaria. Aquatic Mammals. Volume 1, Number 3.

Also see: Water Treatment Protocols for Sealion and Penguin Exhibit