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Performance of an Experimental Wastewater Treatment High‐Rate Algal Pond in Subarctic Climate
Author(s) -
Grönlund Erik,
Hanæus Jörgen,
Johansson Erica,
Falk Stefan
Publication year - 2010
Publication title -
water environment research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.356
H-Index - 73
eISSN - 1554-7531
pISSN - 1061-4303
DOI - 10.2175/106143009x12487095236478
Subject(s) - subarctic climate , wastewater , environmental science , sewage treatment , environmental engineering , ecology , biology
A pilot‐scale experimental high‐rate algal pond (HRAP) was investigated in the subarctic mid‐Sweden region, at latitude 63°N. During autumn 2002, conditions included temperatures below 10°C and photosynthetic active radiation below 200 µE/m 2 ·s. Biochemical oxygen demand was reduced by approximately 90% (approximately 40 g/m 3 ), chemical oxygen demand by 65% (approximately 80 g/m 3 ), total phosphorus by 20% (approximately 1 g/m 3 ), and total nitrogen by 46% (approximately 15 g/m 3 ), at a retention time of approximately 2.5 days. During autumn 2003, the performance of the HRAP appeared better with a more dense microalgae culture; however, as a result of poor settling of the microalgae, the reduction was considerably lower. A major difference between the years was the microalgae composition. In 2002, the large green algae Coelastrum dominated with Chlamydomonas , Scenedesmus , Lagerheimia , and the Cryptophyte Rhodomonas . In 2003, there was a total dominance of the very small green algae Chlorella , known to be difficult to settle. In batch growth experiments during spring 2002, doubling times of 4 to 6 days were achieved. The period of temperatures above 10°C and an insolation of more than approximately 270 uE/m 2 ·s (125 Langleys), which is well‐documented as appropriate for HRAP function (Oswald, 1988a, 1988c), were measured to last for 4 to 4.5 months from early May to late September. However, the growth and treatment performance experiments indicated that a longer season may be possible—6.5 to 7 months, at best—from early April to late October.