BioE 411 and AE/CE/BRT 511Wastewater treatment

Attached growth systems: sewage farms

Morestead sewage farm

Berlin sewage farm layout

Sewage farm

Overland flow designs

Improved attached growth:early biobed

Large-scale wastewater treatment

Rotating disc arrangement

Simple treatment: septic tank

Leach field after septic tank

Suspended growth systemsSo far, we have studied systems where treatment is effected by bacteria, and other organisms, which are attached to a solid medium, i.e. soil, rocks, etc. There are also systems where the microbial growth occurs in suspension. The bacteria then aggregate into flocs, which are barely visible to the naked eye, but each consists of millions of bacteria and often protozoa attached to the floc.

Systems range from the simple facultative lagoon or pond, with no aeration, to aerated ponds and to sophisticated activated sludge systems, where the biomass is separated from the effluent and recycled to treatment and excess production treated separately.

The simple lagoon or pond systems purify the water quite well, but since there is no provision to separate the biomass production, the effluent is quite turbid and still contains much organic material, but stabilized to a non-smelling and not rapidly degrading form.

Facultative lagoonsFacultative lagoons or stabilization ponds use only natural phenomena and almost no mechanical action. Oxygenation for bacterial oxidation of organics comes from photosynthesis by algae and a bit from wind. CO2 released by bacteria is used by the algae. Excess biomass and other settleables are treated by anaerobic bacteria at the bottom.

Facultative lagoon interactionshttp://www2.bren.ucsb.edu/~keller/courses/esm223/esm223_15.pdf

Design approaches to pond treatment systemsPonds usually require lengthy treatment periods, weeks for facultative systems and days for aerated systems. Although facultative systems have very little mixing other than inflow, gas bubbles and wind effects, the long retention periods ensures some homogeneity except with respect to depth, as there is much stratification.

As in any mixed system, the contents have the same concentration as the overflow. This means that the organisms in the pond continuously experience a low level of substrate to feed on, which slows down the treatment considerably, as the typical first-order reactions are directly proportional to the BOD. Therefore, significant improvement in treatment rate can be achieved by approaching a channel (tube) flow, or using multiple ponds.

Multiple pond system analysis can be performed by assuming that each is a completely mixed system, operating on a first-order degradation and a mass balance around each provides one equation. Intermediate values can be eliminated as of no interest, so the solution will provide final effluent quality for given retention times, or more importantly, retention times to achieve a necessary effluent quality.

Activated sludge process

Activated sludge flocsNote filamentous bacteriaNote Vorticella and other protozoa

Activated sludge modelLL0LLLL

Activated sludge plantsHyperion, Playa del Rey, CA)

Primary aeration tank

Oxygenated systemsCryogenic air separation facility, Hyperion, Playa del Rey, CA)

Settling tanksSecondary settling tank, Hyperion, Playa del Rey, CA)

Aerobic suspended systems activated sludge

Volumetric loading = QL0/V

QL0

Nitrogen removal Nitrification (Nitrosomonas and Nitrobacter) NH3 + O2 NO2- NO3-

Denitrification

NO3- + organics CO2 + N2

Process adaptations

AnoxicAerobicAir

Phosphate removal BNR plants

Discarding phosphate anaerobically

Luxury aerobic uptake of P in aerobic stage

Process adaptations for N and P removalAnaerobicAnoxicAerobicAirWastewater

Excess biomass disposal Production

Separation

Further biological treatment (an)aerobic

Dewatering

Drying solar or gas heated

Disposal/ beneficial use soil amender/fertilizeror fuelThe cost of biomass disposal amount to about half the cost of wastewater treatment. Aeration, if used, almost up to half of the rest of the cost. If no aeration, the capital cost , including the cost of land, could be very high.

Typical steps in modern wastewater treatment

How are living beings classified?Historic development of classification

Linnaeus (1735) 2 kingdomsHaeckel (1866) 3 kingdomsChatton (1925) 2 groupsCopeland (1938) 4 kingdomsWhittaker (1969) 5 kingdomsWoese (1977,1990) 3 domainsAnimaliaAnimaliaEukaryoteAnimaliaAnimaliaEukaryaVegetabiliaPlantaePlantaePlantaeProtoctistaFungiProtista(not treated)ProtistaProcaryoteMoneraMoneraArchaeaBacteria

How are living beings classified?

Two super- .kingdoms Three domains Six kingdoms

Mineralia non-lifeBiota/ Vitae lifeAcytota / Aphanobionta (Viruses, Viroids, Prions?, ...) non-cellular lifeCytota cellular lifeProkaryota / Procarya (Monera)BacteriaEubacteriaArchaeaArchaebacteriaEukaryota / EucaryaProtistaFungiPlantaeAnimalia

Carl Woeses Tree of Life