TAHTA waste water treatment plant is a (WSPs) constructed for treatment the domestic waste water of TAHTA city which located at a latitude of 26˚42' N and a longitude of 31˚41'E and it is about 91.00 m above the sea level. The performance of TAHTA plant along the three years of study period is estimated in the form of a comparison between the results of the total system or its components with the allowable values of the studied parameters, or in a relation between the input and the output of these parameters as efficiency. The final effluent characteristics are compared with the designed ones and with those recommended by Egyptian Code of Practice (ECP) and Food and Agriculture Organization (FAO) for re-use of water treated by this type of treatment. The existing operation is considered as unrealistic because of the deviation of its input flow parameters from the designed ones. The plant ponds were designed for full capacity flow rates, recommended influent BOD, etc. So, this research aiming to: 1) Evaluate the performance of the plant under existing operation conditions. 2) Examine whether the treated water quality in the range of standards set by (ECP) for this type of treatment. 3) Identify the problems associates with the plant. 4) Suggest ways to improve the performance of the treatment plant. The study is performed experimentally where the daily sampling and laboratory analysis were carried out according the standard specifications. The study revealed that 1) Plant system is working satisfactory in the period of study to fulfil the requirement of use its treated water in irrigating forest trees which is the one of its construction purposes. 2) As the performance of the plant did not meet the design one at the operation parameters such as low flow rate and low coming BOD5 loadings for treating some parameters due to sludge accumulation in anaerobic ponds, or because the incoming rate of sewage in 2016 is higher than the plant design capacity. So; a) Sludge accumulated in anaerobic ponds should be removed when its depth reaches 1.00 m according the design recommendations or when it is one half full of the sludge by volume [13]. b) Flow distribution should be checked to be uniform otherwise a short circuiting problem is faced. c) Inflow rate must be checked otherwise, to receive more of sewage inflow coming from the surround area than its design capacity some modifications may be used to improve (WSPs) efficiency. 3) According to (ECP) and (FAO) recommendation, the treated wastewater from TAHTA plant is acceptable for re-used in the irrigation of wooden tree forests.