Dear Dr Hans Brix,

Thank you Dr. Brix for you comments and questions of May 14 on Frederick, MD.

The paper on the Frederick, MD facility was prepared by the authors several years ago.  It referred to a Living Machine which was built in 1993 and was the first of four EPA demonstration projects.  Current Living Machine design has moved on to a further generation of our design thinking since then.

I believe the MD Living Machine demonstrated excellent performance in the last year of operation (1995-1996).  Unfortunately during a critical ten-week period in early 1995 when Sherwood Reed P.E. was analyzing data, there was an upset condition at the facility.  Aeration was lost for a period owing to blower failures and at the same time the strength of the incoming waste was substantially above design owing to changes in the protocol of the County. This was caused principally by construction at a nearby facility which took the headworks off line.  It was also combined with high loads of septage during the same period.  However after the system settled down, the performance of the Living Machine was excellent (with the possible exception of phosphorus treatment) for the remainder of the demonstration project.

We also believe that the report was unduly harsh on the operation of this Living Machine.  Certain of the authors had conflicting agendas and we believe that the criticisms of the plant by these authors was not exactly unbiased.  Other reports are available, which were written by the main EPA contractor which together with the minutes of the prestigious Technical Advisory Group provide a whole different view of this particular Living Machine.

The following are comments on your five detailed points.

1.      We completed disagree that the plants in Living Machines are marginal to the treatment.  The report authors were wrong and unscientific in their conclusions.  It is necessary to view a Living Machine as a sequence of engineered ecosystems where the diversity of biological life plays the significant role.  The comments in the report were made following a period when plants were removed from two tanks in one train for a short period of weeks.  There continued to be biological momentum in the system and there was recycle to these tanks from other tanks in which there were higher plants. We believe the test outlined in the report is quite invalid.

        We are currently running EPA-approved tests at our South Burlington facility which will establish the contribution of higher plants to the performance of Living Machines.

2.      We disagree with the comments with regard to sludge.  The Maryland facility generated approximately 0.4 kg of sludge (dry weight) per kg of BOD removed.  The corresponding figure for South Burlington, which does not have an anaerobic reactor, is 0.55 kg of dry solids/kg of BOD reduced.  These figures are substantially better than those for an activated sludge processes and are in the best range for extended aeration.

3.      The life cycle costs enumerated in the Report were based on "apples and oranges" data.  Despite numerous protests, the authors refused to adjust the numbers.  In the current EPA report which will be published later this year, Living Machines have lower life cycle costs than conventional technologies at all sizes designated for evaluation by the EPA.  For this new report the sizes chosen were 40,000 gpd, 80,000 gpd and 600,000 gpd.

4.      The question of solar energy playing a role in treatment is a design question.  At Maryland the main contribution of solar energy was in maintaining water temperature in the greenhouse and in the growing of the plants.  The plants make a significant contribution to Living Machine performance.  There are other designs of Living Machines where the direct action of solar energy on photosynthetic microorganisms is significant.

5.      The authors of the Maryland report made many attempts to "put down" the advances that have been made in ecological engineering.  It is rather like saying a BMW or a racing car is just like any ordinary car with four wheels, an engine, a drive shaft and a body.  It is true that Living Machines do use air and do use nitrification and denitrification processes.  However as has been demonstrated on many sites, Living Machines provide reliable, low cost treatment in attractive facilities with minimum inputs and performance results that are highly stable.

        We are of the firm view that an ecological engineering approach to wastewater treatment as demonstrated by Living Machines is indeed a distinct technology.  Evidently our many clients agree.

Michael Shaw,
Presedent, Living Technologies Inc.,
431 Pine Street, Burlington,Vermont 05401
Tel: 802 865 4460, Fax: 802 865 4438
http://www.livingmachines.com