What are the system design limitations and shortcomings of conventional 9” disc diffuser fixed grid systems?
System turn down limited by pin hole balancing orifice design - no system turndown – see question #4 above
Not capable or only limited capability of nutrient loading driven process design
Represents a single point of design reg. SOTE to projected nutrient loading optimization on a yr. 1 to yr. 20+ planning time scale
Reduced expected product life due to operating below min. allowable system airflow of typically underloaded plants (40% to 60% of max. plant capacity) – clogging of diffuser membranes
High number of diffusers needed, high number of connecting points, high number of linear ft [m] of lateral air piping
Convoluted lateral air pipe system with a multitude of rigid couplings and connection points subject to material fatigue especially under oscillating / changing loading condition / temperature change caused expansion & contractions.
Cumbersome and non-reliable disc diffuser membrane in field replacement
TRADITIONAL 9” Disc condensation moisture purge system – Limitations of EDUCTOR PURGE LINE SYSTEMS?
Functions only at maximum water depth: traditional purge lines operate on
differential, similar to a manometer. when the waterlevel drops, there is not enough
differential pressure inside the air header piping to lift the condensate high above
the water level
Manual operation - eductor purge lines require frequent manual opening of systems
Entire piping grid may not be purged – eductor purge lines have a single sump to
accumulate condensate. air velocity may trap condensate away from sump. airflow to
grid may have to be temporarily shut off to allow condensate to collect in the sump
SOTE Benchmark Testing disc, tub, & strip diffusers – 1996 - 2018 Optimizing SOTE performance of fine bubble membrane diffuser system since the 1980s
Summary single column testing – [ see also BENCHMARK & FAQ for further reference]:
Single column testing is an objective tool comparing the relative SOTE performance of diffuser model and manufacturers
Single column testing results are not suitable as basis for mass transfer modeling programs and diffuser system design
The need for diffuser grid balancing and the limitations in turndown range of some diffuser models need to be considered in yr. 1 to 20+ planning diffuser model and manufacturer benchmarks
Only single column & full-scale testing by 3rd party, independent & accredited testing institutions / laboratories shall be permissible for diffuser model & manufacturers SOTE performance testing evaluations
Test should be performed in compliance with the latest ASCE clean water / ATV M 209 SOTE testing standards
Full scale independent, & accredited3rd party ASCE clean water / ATV M 209 compliant SOTE testing is needed for diffuser model & manufacture benchmark, mass transfer modeling programs and diffuser system design
Product limitations of PFTE coated EPDM Disc and Tubular Diffuse membranes:
PFTE – Teflon coated membranes are a laminate of a PFTE – Polypropylene [PP] plastic blend bonded to a flexible EPDM membrane
It is approx. 2+ x more expensive than pure EPDM membranes
Laminating of coating after short period of time 6 to 24 month
Not protecting diffuser’s air release point, slits / pores
Addressing the symptom of clogging, but not the root cause of lag of system turn down range of disc and tubular diffuser system
Health & environmental concerns:
The manufacturing process, its by-products, and industrial waste products of non-stick products using PFOA and PFOS, [two chemicals in a class known as PFAS] are known to be cancer causing and have been contaminating US ground and drinking water, food supplies since the 1970s.
Since the early 2000s Companies like 3M and Dupont closed their US manufacturing sites, spun off their PFOA divisions, and/or off-shored them to China and Brazil due to the above concerns.
PFTE coating lamination contributes to micro plastic / particle counts in rivers, lakes, & oceans
Recommended / preferred fine bubble diffuser membranes materials: