Department of Food, Agricultural, and Biological Engineering
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Student Projects 2002

Living System photos

Living System Website

 

 

 

 

 

FABE 652
Ecosystems for waste treatment

Lecture #6
Case Study of Solar Aquatic Systems (SAS)

 

Solar Aquatic Systems (SAS)
Hamersley et al. Nitrogen balance and cycling in an ecologically engineered septage treatment system. Ecological Engineering. 2001. 18: 61-75. Marion MA

Influent=2200 liters, with recycle =2933 liters

1.     SAS Components (overhead Fig.1 ’01, Fig.1 ’96)

  • Equalization tanks - blends influent to reduce variability. Seeded with bacteria preparation. V=19000 liters, 8.6 day HRT.

  • Preliminary cond. Tank - Only in Marion. 3:1 mix of influent and biosolids from 2nd clarifier. V=3800 liters, 1.3 day HRT
  • 1st Clarifier - Removed largest part of solids and nutrients in each system. Major difference from burlington and our systems. Why important to waste biosolids early in this system? V=3000 liters, Q= 2600 l/day, HRT=1.15 days.
  • Aerated Aquatic Tanks - 2 parallel lines of 9 tanks, V=620 l, HRT=.48 d, total V=11200 l, HRT=4.3 d, air Q=1 m3/hr (D.O.>5 mg/l). plants-willow (other trees), water hyacinth, pennywort, primula, mint,; depth=1.5 m, root depth is 30 cm or 20% water column. algal/bacteria mat-zooplankton, nematodes, snails
  • 2nd Clarifiers - V=620 l, HRT=.48d, 30% of flow recycled to prelim. Cond. Tank.
  • Subsurface wetlands - HRT=3.5d, polishing and denitrification

2.      SAS Performance (overhead Tab 1,2 ’01, Tab 1,2,3 ’96)

  • Marion facility large reductions (except NO3). Treats to tertiary stnds. Better than conventional Orleans facility.

  • Nitrogen (fig.5 ’01) - >80% removed in prelim trt., low plant uptake, denitrification throughout system-microsites, initially added acetate as carbon source to wetlands.
  • Phosphorus - reduced by 97% to 1.5 mg/l w/out precipitates
  • Resiliance - during draining, increased flow and loading effluent conc. Remained low (p.143 ’96)

 

5.      Nitrogen (overhead)

  • Removal 57% by clarifier, 40% denit, 0.5% plant uptake, 1% effluent. 94% N entering greenhouse removed by tanks/wetland
  • Greenhouse % N removal insensitive to varying loading rates. More mass N-more removal (fig 2)
  • Review of N cycle p.63 know for midterm (overhead N cycle)
  • Mineralization (Org N to NH4) – great reduction in orgN in prelim trt removed as solids (62%), in prelim tanks mine. Possibly limited by oxygen levels, increases in inorg N in the aquatic tanks as solids biodegrade (Fig. 3 ’01)
  • Nitrification (NH4 to NO3) – in prelim. Trt. Decline in NH4 shows nitrification in excess of mineralization, decrease of NH4 in aquatic tanks (fig.3&4a ’01), dependent on biofilms on walls, plant roots, suspended particles, conc of nitrifiers increases through system
  • Denitrification (NO3 to N2 gas) – high denit rate in prelim trt, NO3 conc increased in aquatic tanks (fig.3&4 ’01)-denit limited by org C and anaerobic sites, Plant roots support denit???, Removing many solids early limits carbon source for denit and had to add acetate

6.      Extra Points

  • Extra-overall lower costs (p.143 ’96)
  • Waste solids production low 0.81 g/g TSS vs 1.3 g/g TSS conv. Orleans facility
  • Methods-count bacteria, measure flowrates (effective mixed volume?)