Properties of biotite as filter material in sand filter beds

1. Properties of biotite as filter material in sand filter beds 11.10.2007 Lakepromo seminar, Budapest Ville Matikka Savonia university of applied sciences Kuopio Finland

2. In Finland about million inhabitants live in houses that are not connected to centralized sewerage systems. • About 350,000 permanent residences and 450,000 holiday homes must treat their own wastewater 'on site' The percentage of water in the area

4. The onsite wastewater system degree (1.1.2004) • BOD7 reduction should be at least 90 % • Total phosphorus reduction should be at least 85 % • Nitrogen removal should be at least 40 % • The requirements in the Decree applied immediately to all new buildings • Old buildings should fulfil the new standards by 1.1.2014

5. Sand filter bed

6. A common sand filter bed Distribution pipes Distribution layer Chippings 16-32mm Biofilm layer Sand filter layer 0-8 mm Collector layer Chippings 6-16mm Underdrain

7. Problems with current sand filter systems • A majority of current small scale wastewater treatment systems will not fulfil the new criteria considering nutrient removal and recovery • In sand filter beds the average of total phosphorus reduction is 25-80%, total nitrogen reduction 10-80% and total BOD reduction 85-97%

8. How can we improve the sand filters? • Reactive filter materials can be used to increase the phosphorus and nitrogen removal from small scale wastewater systems • Usually reactive materials are put in a separate filter unit that follows the traditional sand filter bed • Finland's environmental administration studied the sand filter beds and has noticed that filter beds with reactive filter materials are more efficient than the traditional ones

9. Biotite • Biotite was one of the reactive filter materials studied by Finland's environmental administration • Biotite is a common sheet silicate mineral where iron, magnesium, aluminum, silicon, oxygen, and hydrogen form sheets that are weakly bond by potassium ions • Biotite may be used as part of an usual sand filter layer and no separate reactive filter unit is needed • Biotite does not require any maintenance: other reactive materials must be replaced once per year • In Finland biotite is a by-product in production of fertilizer called apatite. A company Kemira Grow-How produces locally lots of apatite (and biotite).

10. Motivation • It has been seen that sand filters that contain biotite work better than usual sand filters, but the reason is partly unknown. • Kemira Grow-How is also motivated for finding new applications for biotite

11. Test environment

13. Parameters measured from wastewater • Phosphorus (total and dissolved) • Nitogen total • Ammoniacal nitrogen • Nitrate • Nitrite • BOD • COD • pH • Parameters that indicate the microbiological activity of the sand filter.

14. Test results: Phosphorus reduction

15. Test results: Nitrogen reduction

16. Incoming water Out coming water Ammoniacal nitrogen (NH4) / Nitrate (NH3)

17. Test results: BOD reduction

18. Conclusions from the first few months: • Wastewater spreads more equally over the filter because biotite permeability is smaller than for sand -> As a consequence biofilm spreads more equally over the filter -> Wastewater doesn’t permeate too quickly throughout the sand filter layer so the micro-organisms have more time to use wastewater as a nutrient Distribution layer Biofilm Sand filter Biotite layer Sand filter Collector layer

19. During the rest of the project we will: • Study the microbiology of sand filters • Is biotite a better growing base for bacteria than sand • Focus more on chemical absorption • Pay more attention to the structure of the sand filter to further improve its properties

20. Thank you!