N-ViroTech® - a novel process for the treatment of nutrient limited wastewaters

Abstract

As pulp and paper wastewaters are mostly deficient in nitrogen and phosphorus, historical practice has dictated that they cannot be effectively treated using microbiological processes without the addition of supplementary nutrients, such as urea and phosphoric acid. Supplementation is a difficult step to manage efficiently, requiring extensive post-treatment monitoring and some degree of overdosing to ensure sufficient nutrient availability under all conditions. As a result, treated wastewaters usually contain excess amounts of both nutrients, leading to potential impacts on the receiving waters such as eutrophication. N-ViroTech is a highly effective alternative treatment technology which overcomes this nutrient deficiency/excess paradox. The process relies on communities of nitrogen-fixing bacteria, which are able to directly fix nitrogen from the atmosphere, thus satisfying their cellular nitrogen requirements. The process relies on manipulation of growth conditions within the biological system to maintain a nitrogen-fixing population whilst achieving target wastewater treatment performance. The technology has significant advantages over conventional activated sludge operation, including: Improved environmental performance. Nutrient loadings in the final treated effluent for selected nitrogen and phosphorus species (particularly ammonium and orthophosphate) may be reduced by over 90% compared to conventional systems; Elimination of nitrogen supplementation, and minimisation of phosphorus supplementation, thus achieving significant chemical savings and resulting in between 25% and 35% savings in operational costs for a typical system; Self-regulation of nutrient requirements, as the bacteria only use as much nitrogen as they require, allowing for substantially less operator intervention and monitoring. This paper will summarise critical performance outcomes of the N-ViroTech process utilising results from laboratory-, pilot-scale and recent alpha-adopter, full-scale trials.

Development and examination of a granular nitrogen-fixing wastewater treatment system

“…The organic load to both systems was representative of a moderate strength pulp and paper mill effluent [2]. The temperature of the reactors was controlled at 30 8C, elevated above that used in most granular work, but representative of conditions in industrial effluents emanating from processes such as pulp and paper mill operations.…”

“…However, some industrial waste streams, such as discharges from pulp and paper mills, have an extremely low ratio of nitrogen to carbon. For biological treatment of these nitrogen deficient waste streams, novel processes that utilise nitrogen-fixing bacteria may be employed [1,2]. The diazotrophic organisms in these systems are able to directly fix nitrogen from the atmosphere, thus satisfying their cellular nitrogen requirements, while maintaining extremely low nitrogen discharges in the final effluent [3].…”

The effects of nutrient limitation (nitrogen and phosphorus) on BOD removal from post-coagulated Pinus radiata sulfite pulp and paper mill wastewater in a baffled aerated stabilisation basin–laboratory pilot scale study

“…With general industry accomplishment of removal of acute toxicities, e.g. Biological Oxygen Demand (BOD), Adsorbable Organic Halogen (AOX), and resin acids (Slade et al 2004) in developed countries, regulatory authorities have focussed subsequently on chronic effects within the receiving environments, such as eutrophication from nutrient input (Slade et al 2004). Hence, the industry experiences pressures from regulatory authorities and the community to address current and existing problems in an order of priority based on the level of known impact on the environment.…”

“…Nutrient loads in wastewaters of pulp and paper mills are generally considered limited with respect to N and P requirement for bacterial growth (Slade et al 2004). Therefore, the stage of the process where such a coagulation treatment step is to be implemented into the overall process becomes an important consideration, in particular where specific nutrient loads are required for subsequent biological treatment prior to discharge.…”

“…From this data it can be seen that, by increasing the HRT of ASB simulations, low N and P to BOD ratio wastewaters can be treated for high percentage removals of BOD and nutrients. The control of nutrient by addition to pulp and paper mill wastewater using a N-ViroTech process was conducted by Slade et al (2004) using three different types of pulp and paper source waters. The BOD:N:P ratios were set at 100:0.6-0.7:0.4; 100:0.5-1:0.3-0.4 and 100:0.9:0.15 with 10 days of HRT.…”