TM 5-814-3/AFM 88-11, Volume III
h. Land application. Land application of secondary treatment effluent can be used effectively as a
means of phosphorous and nitrogen removal, biochemical oxygen demand removal, and solids removal. Since
there is not a direct discharge to a receiving stream, land application in many instances is an attractive
alternative for advanced treatment.
9-3. Plant site preparation.
Site drainage is an important factor in design of wastewater treatment facilities. Capacities of drainage
structures will be designed in accordance with requirements of TM 5-820/AFM 88-5 series. All treatment
9-4. Plant layout.
a. Arrangement of treatment units. The first step in determining the best arrangement of units is to
arrange all units sequentially according to the flow of wastewater through the system. The resulting hydraulic
profile for wastewater flow will determine the relative vertical alignment of each of the plant units. Final
arrange-ment of the units then results from adaptation of site features to the treatment plant's functional and
hydraulic requirements. Allowance must also be made for the area of operation and maintenance of the
treatment units. If sufficient head is available for gravity flow, the hydraulic requirements will control the
plant layout. Greater flexibility in arranging the treatment plant units is achieved with intermediate pumping
of wastewater. The treatment plant must operate during emergency conditions such as power failures and
also during periods of maintenance work on treatment units. Dual units should be provided in all feasible
cases to provide operational reliability and flexibility.
b. Conduits and pipelines. Conduits and pipes will be arranged in such a manner as to reduce space
and cost requirements. They will be designed to handle the expected maximum flows through the treatment
plant. Design requirements for pipes and conduits are found in TM 5-814-1/AFM 88-11, Volume 1.
c. Bypasses and overflows. Provisions for bypassing individual treatment units will be made so that
each unit can be taken out of service without interrupting the plant operation. Bypasses will not be provided
for screen, chlorination units, nor other unit process where duplicate units are available. Overflows will be
used to prevent hydraulic overloading of treatment units, especially biological treatment units. Return of
flows or temporary storage of wastes not treated or alternate treatment must be provided. Refer to facility
discharge permit for limitations on plant component bypasses and overflows.
d. Future expansion and flexibility. The plant designer will consider provisions for expansion by
allowing sufficient space for additional units (and additional conduits) to be installed in the future. The plant
will be designed so that installation of additional units or repair of existing units will not disrupt operations.
e. Treatment plant discharge. Outfall sewers will be extended to the low-water level of the receiving
body of water or to submergence required by regulatory authority to insure satisfactory dispersion of the
plant effluent. Provisions for effluent sampling and monitoring are required. The design will assure the
structural integrity of the outfall, prevent failure due to erosion, and prevent back-flow during flooding.