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Overview

Innovative Water Solutions Ltd (IWS) is pleased to provide technology for the treatment of domestic and industrial waste water to the South Pacific. The technology is based on the Permanently Submerged and Aerated Fixed Bed. This advanced bio-film system, in various sizes and configurations, is suited to domestic and industrial waste treatment applications. We believe the IWS designed Permanently Submerged and Aerated Fixed Bed system leads currently available technology in decentralised wastewater treatment.

Although new to the New Zealand market, similar technology has been operating successfully for the past 10 years in Europe. The systems offered are compact and of modular construction. Total site area requirements are less than 60% of conventional systems. Odour production is minimal, and contained in the pre-clarification stage, and no odour is produced in the final clarification stage.

Process Description

The SUBMERGED FIXED-BED is a continuously operating fully biological aerobic wastewater treatment procedure. It is based on bio-film technology using a bio-film carrier made of synthetic material as a base for sessile (i.e. clinging to the surface) micro-organisms, which are responsible for the actual sewage clarification.

The oxygen supply is guaranteed by blowing air from below into the stationary fixed-bed. The synthetic bio-film carrier blocks are of manageable size, and made of ecologically beneficial polyethylene with specific surfaces of between 100 and 200 m²/m³. These synthetic blocks have also proved their value in the well-known trickling filter technology. They are solidly locked to the tank via stainless steel brackets. Therefore, hydraulic problems, as they are known in fluidised bed procedure, do not occur in this process. Rubber membrane diffusers provide the air ventilation. The diffusers do not have any movable parts and because they produce ultra-fine air bubbles they are extremely efficient. The application of rubber membranes made of EPDM guarantees a continuous oxygen supply and their flexibility prevents blockage of the pores (commonly happens when using ceramic diffusers). The rubber membrane diffusers are also widely used in activated sludge plants.

By aerating the fixed-bed turbulence is created. The shear forces in turn cause a tearing of the sludge flocs cling to the fixed-bed surface, thus allowing these to be carried to the final clarification stage. As is well known from other bio-film technologies these compact flocs can easily be disposed of. The flocs are recycled from the final clarification tank to the pre-clarification stage. In the case of single tank sewage treatment plants, the flocs are stored in the pre-clarification tank. In the case of larger systems the flocs are stored in an external sludge storage tank.

More information and pictures on this process can be found here.

Advantages

IWS design and construct state of the art treatment systems design suitable for waste water treatment in single households (4-50 PE) up to communities of 20,000 PE (Population Equivalents). The IWS bio-film system is a fully automatic biological process using a permanently submerged and intermittently aerated fixed-bed.

This system utilises the best characteristics of the trickling filter technology with those of the activated sludge procedure, while at the same time avoiding their only too well-known handicaps.

Several further advantages of this system are:

• Compact constructions with simple tank designs mean only small demand on space. Conventional procedures require 0.7-1.0 m³ per person - the IWS technology requires only 0.4 m³ per person. Saving substantially on area requirements, building material and on civil engineering costs.
• The sludge volume generated by the bio-film system is up to 70% less than conventional procedures. This can be even further reduced if the turbid water is re-pumped from the final stage to the primary clarification. In existing systems 1.5-3 litres of sludge per person per day are normally produced. The IWS system will reduce this to 0.75 litres per person per day, a major saving on sludge handling and disposal.
• A sophisticated technique of intermittent aeration (rubber membrane diffusers) feeds the proper dosages of oxygen to the micro-organisms. Free oxygen is then available to allow various populations of sessile bacteria to form a three layer bio-film. Since they do not tumble around in the tank, but are immobilised in and on the IWS fixed-beds these populations are able to adapt quickly to different conditions. Transient pollution loads or occasional slight toxic inputs can thus be much better absorbed. The learning capability of the micro-organisms is enhanced and "experiences" are passed onto following generations.
• A unique factor of this system is the intricate aeration system. IWS systems generate a pattern of stationary waves in the waste water. Their specific shearing forces tear off the sludge flakes clinging to the fixed bed surface, and agitating the bio-mass at the same time. This gives a high degree of stability and operational reliability.
• The biological stages are installed in modules and can be utilised partly or completely according to demand. That makes them optimal for maintenance and operation in seasonal applications such as hotels, motels, camping sites etc.
• Power costs are minimised due to the high degree of efficiency offered by both the extremely fine-bubble aeration (laser-cut tubes) and the sophisticated, fully automatic control unit. Maintenance requirements are reduced to a minimum thus saving costs on operational personnel. Since there are no submerged moving mechanical parts, the need for repairs is practically nil. Also the common danger of clogging the carrier media is now a problem of the past.
• There is hardly any incident of filter flies or other insects. Unpleasant sewerage odours in the pre-clarification stage (common to other technologies) is avoided. There is no odour in the biological treatment stage.
• The excellent effluent quality permits the use of the purified wastewater for underground irrigation of green areas, parklands etc. This is particularly suited to warm climates, specifically tourist areas.
• IWS offers decentralised systems in concrete, stainless steel or plastics from 4 to 20,000 PE.
• IWS grants an operational guarantee of 15 years on the procedure of the submerged fixed-bed.
• IWS guarantees to conform to all effluent rates set by NZ and Australian regulatory bodies.