Research and discovery

Dr James Barnard has had a significant influence on the development of wastewater treatment systems. His scientific breakthrough, the Bardenpho process, laid the foundation for all ensuing BNR systems. Frank Rogalla assesses Dr Barnard's considerable legacy

Doctor James Barnard turned 70 years old on June 6, 2005. He has transformed contemporary wastewater treatment with the discovery, development and advancement of biological nutrient removal (BNR) principles and processes.

The activated sludge process was originally developed by Ardern and Locket during the first world war. By the mid-20th century traditional WwTWs were successful in decreasing concentrations of organic pollutants, suspended solids and pathogens. In the early 1960s, nitrification with activated sludge was explored by Downing and Painter at WRc.

The need to decrease total concentrations of nitrogen and phosphorus, however, became critically apparent as increased nutrient loads in treated wastewater effluents provoked highly undesirable effects in the aquatic biosystem, including eutrophication and related algal blooms, fish kills and anoxic and hypoxic events.

Following the completion of his PhD work in the US in 1971, Dr Barnard returned to his home country of South Africa (SA) and focused his energy on local wastewater issues. At that time, water shortages and eutrophication were becoming serious problems in SA. Although chemical methods had been developed at the National Institute for Water Research (NIWR) to remove nitrogen and phosphorus, these processes raised serious questions in terms of cost, dependability and environmental impact. Dr Barnard began focused research on biological methods of removal of nitrogen and phosphorus.

Starting from the method proposed by Balakrishnan & Eckenfelder at Vanderbilt University where he obtained his PhD, using a combination of contact-stabilisation and attached growth nitrification, the process was simplified to pre-denitrification/nitrification, later named Modified Lutzack Ettinger (MLE). With the addition of a second anoxic and re-aeration zone, more than 92% nitrogen removal could be achieved without addition of chemicals. These findings were published in 1972 in the Journal of the Institution of Water Pollution Control. This four-stage nitrogen removal process was subsequently patented in the US by NIWR under the name Barnard Denitrification and Phosphorus removal (Bardenpho). Within three months of the development of this revolutionary process in the laboratory, the concept was accepted by the City of Johannesburg for the design of the new Goudkoppies nitrogen removal plant for 750,000PE. A 100m3/d pilot plant was constructed for further exploration of Bardenpho.

Chemical precipitation

Phosphorus profiles revealed at times residual concentrations of less than 0.2mg/l. Some prominent researchers attributed this effect to biologically induced chemical precipitation. During two years of dedicated studies Dr Barnard observed the correlation of phosphorus and nitrates in the effluent. Phosphorus removal was not effective when the nitrate concentration was high.

He noted when phosphorus was removed by biological means, a zone was needed where phosphorus was released. He concluded there was no role for nitrates in chemical precipitation and that it must be a biological mechanism with a need of an anaerobic phase, defined as the absence of nitrates and dissolved oxygen, followed by an aerobic stage.

Dr Barnard's scientific breakthrough and subsequent research and testing formed the foundation upon which all ensuing BNR innovations and modifications are based, some developed by him and some by other researchers. His work in enhanced biological phosphorus removal (EBPR) was based on the natural cyclic changes occurring in environmental and nutritional conditions in wastewater treatment. Previously, these phenomena were inadequately understood and it was unknown how to apply the principles in the varied, unstable conditions found in WwTWs. The necessity of anaerobic-aerobic sequencing to stimulate the desired biological processes was understood by intensive, prolonged study of data from full-scale plants accidentally accomplishing EBPR, and smaller scale experiments designed and performed by Dr Barnard.

Further, he determined how to design and operate practical single-sludge nitrification/ denitrification wastewater treatment processes, and then developed practical designs for the combination of EBPR and nitrification-denitrification processes. After other researchers had validated Dr Barnard's initial work the theory was published that biological phosphorus removal was made possible by special organisms that needed acetate or propionate as a feed material. They could take up volatile fatty acids (VFAs) in the anaerobic zones, store them as an energy source and then use this energy in the aeration basin to take up all the phosphorus.

Following his research work with NIWR, Dr Barnard actively designed plants for biological nitrogen and phosphorus removal, and coined the phrase BNR. He proposed the logical place for the anaerobic zone is at the plant inlet.; he proposed flow sheets for high-rate plants with only an anaerobic and aerobic zone (Phoredox) and for a three-stage plant with a sequence of anaerobic, anoxic and aerobic zones with internal recycle to reduce the effect of nitrates in the return activated sludge on the anaerobic zone (three-stage Phoredox).

The concept could also be applied to the four-stage Bardenpho plant (modified Bardenpho) or to carousel systems. These flow sheets were presented as a paper at a meeting in SA in 1975, and published that same year in a north American trade journal. His continued work with the first large BNR plant in the City of Johannesburg resulted in the establishment of key design elements used today in the design of BNR plants, notably:

  • the innovation in use of nitrates as an alternative to oxygen, whereby the overall oxygen input could be reduced,
  • determination of an optimal rate of mixed liquor recycle equal to four times the influent flow Q, beyond which there was no further benefits due to the recycling of dissolved oxygen,
  • discernment that the aeration of return activated sludge return is detrimental to BNR operation,
  • discovery that cascading of the influent due to the steep slope of the plant was detrimental to biological phosphorus removal,
  • the revelation that mixing energy in the unaerated zones could be significantly reduced when using efficient mixing devices.
  • The BNR concept was introduced to the US by the design of the modified Bardenpho plant for the City of Palmetto, Florida in 1978. The plant was required to reduce the total effluent nitrogen to less than 3mg/l and phosphorus to less than 1mg/l. However, the operating cost for chemicals was high and the advantages of BNR plants evident (lower operating cost via reduced chemical and reduced solids).

    Sludge fermentation

    The first year operational results for BNR were an indisputable success, showing an average TN of 2.7mg/l and average TP of less. Dr Barnard was behind the first BNR treatment plant in north America, at Kelowna, British Columbia, Canada, which led to the construction of several other full BNR plants throughout BC. Due to the low wastewater strength and the colder temperatures in Canada, an innovative new component was introduced at Calgary, Alberta, Canada, utilising primary sludge fermentation to enhance EBPR. This modification was initially invented at Olefantsfontein, SA.

    Research had established VFAs were essential for EBPR and the amount available in the anaerobic zone relative to the influent phosphorus would determine the final effluent soluble phosphorus concentration. The influent to the Olefantsfontein plant contained almost no VFAs, so Dr Barnard 'activated' the primary clarifier to accomplish fermentation of the influent organics by increasing the depth of the sludge blanket and accomplished excellent EBPR. He completed the demonstration by showing if fermentation in the primary clarifier was stopped, EBPR would fail. In Calgary, primary sludge was charged to an existing holding tank and thickener, where the sludge was held from four to eight days to optimise acid fermentation but not long enough for methane formation to kick in. The supernatant from this fermenter containing soluble VFA, mostly acetic and propionic acid was then fed to the anaerobic zones of the BNR plant to augment the VFA in the influent. The plant was designed with maximum flexibility to allow for various flow sheets and for changing the retention time of the various zones. During the first year of operation the Calgary plant produced effluent phosphorus of less than 1mg/l. Further enhancements and a better process understanding further improved process performance to achieve an effluent with a yearly average TP of 0.17mg/l. Dr Barnard also designed and supervised the construction and startup of BNR processes in Harare, Zimbabwe, with simplified technology suitable for lower income countries and Windhoek, Namibia with an innovative BNR design. The challenging problem in Zimbabwe and in many parts of SA is that precious water resources must be reused, even if indirectly.

    Dr Barnard developed a low-cost system for biological nutrient removal consisting of a single basin for nitrification and denitrification using surface aerators. Basins were formed by lining ponds, which eliminated the prohibitive cost of concrete structures.

    Platform-mounted surface aerators supplied oxygen, as well as recycling to the anoxic zones and mixing. Most of the aerators were concentrated towards the outlet of the aeration tanks, allowing an anoxic zone at the feed end. This had the advantage of making full use of the influent carbon for denitrification while ensuring the discharge to the final clarifiers were fully aerated to comply with the effluent ammonia requirements of less than 1mg/l. The anaerobic zone consisted of another mixed pond upstream.

    This affordable and innovative 'poor man's carrousel' configuration resulted in a phosphorus removal from about 9mg/l to less than 1mg/l and has had significant impact in water use, reuse and conservation in the developing world. In recent years Dr Barnard has moved his residence, first to Canada and now to the US. For the past ten years he has been an integral member of the Nitrogen Technical Advisory Committee in New York City, optimising the substantial investment towards eliminating eutrophication in the New York Bays. These efforts have resulted in development and adoption of the use of step-feed BNR for most of the 14 large NYC plants.

    He has continued to develop highly-refined processes, such as the design and implementation of integrated fixed film activated sludge systems at several US locations; leading to more economical retrofits for BNR in existing facilities. He has supervised the construction and start-up of BNR processes in New Zealand, Hong Kong and Singapore, as well as filed another patent based on pilot work in Korea. He was also involved in the large SBR plant with nitrogen removal in Dublin, which combines many innovative features, and has participated in the BNR design of the Reading plant in the UK. During June's IWA conference on leading edge technologies in Sapporo, Japan, a special session was dedicated to Dr Barnard and his work. Visit www.let2005.iwa-conferences.org for more information.


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