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detail, which was too long to be covered in this article. However, as mentioned above, influent pollutant concentrations were not always consistent during Phase 1 and the use of two different fertiliser concentrations made it difficult to compare influent and effluent concentrations from the samples collected during this phase. They were therefore only regarded as indicative and were discarded in favour of the results obtained from Phase 2 testing. After the lab test results had been analysed, some of the results were as follows: • The cells using washed aggregates had higher ammonia-nitrogen removal efficiencies than those with unwashed aggregates, while the cell with the raised out let (creat i ng a “sump” i n t he underlying stone aggregate) had the highest ammonia-nitrogen removal efficiency of all. • All the experimental cells appeared to add significant quantities of nitrate nitrogen in quantities which ranged from 160-2 580%. This was probably due to the nitrif ication process of ammonia to nitrate. • The cells with exposed aggregate pavers produced less nitrite-nitrogen and nitrate-nitrogen than the other two types of pavers. • The cell with the raised outlet produced the most nitrate-nitrogen. • The presence of geotext ile had a negative impact on the nitrate-nitrogen removal efficiencies. • When the pH levels were within the optimum range of 7,6-8,8 for the growth of nitrifying bacteria, the nitrification process resulted in a reduction of the ammonia-nitrogen concentration and an increase in nitrate-nitrogen concen tration. Lower pH levels resulted in higher nitrate-nitrogen concentrations. • The removal eff iciencies of ortho phosphate-phosphorus ranged from
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37-11%, compared with the mean of 47,7% removal rate of orthophosphatephosphorus in other studies. The presence of a geotextile resulted in a higher orthophosphate-phosphorus removal efficiency than those without. The cells with washed aggregates had higher orthophosphate-phosphorus removal efficiencies than those with unwashed aggregates. The cell with the raised outlet had the lowest orthophosphate-phosphorus removal efficiency of all, which might have been caused by the fine particles being slowly washed t hrough t he permeable paving and desorption due to the lack of useful adsorption sites. T h e p a p e r c o n c l u d e d w it h t h e observation that while PICP is effective in removing ammonia-nitrogen, it does so at the expense of an increase in nitritenitrogen and nitrate-nitrogen. The authors recommend further research to establish whether the creation of an anoxic zone, coupled with introduction of a suitable electron donor to the PICP, could address this shortcoming. • A full copy of the paper can be down loaded at: http://dx.doi.org/10.3390/ w12061714. (Above): A typical cross-section of the PICP test cells. (Below): Paver types: (a) Aquaflow®, (b) Permealock® and (c) standard exposed aggregate.
