IOA News Letters Summary

by Prof. Hua, Jian, National Taiwan Ocean University IOA potential member R.O.C.

Introduction

Water sources for KinLuen Bay Park include deep ocean water, stream, hot spring, groundwater, and tap water. Discharge and treatment of wastewater can be complicated by the characteristics and flow rates of mixture from various effluent sources. This paper suggests alternatives to conventional water treatment, based upon various possibilities of use and mixing of water. It is aimed at establishing a water treatment model which may be feasible environmentally and economically, including land treatment and reuse of wastewater for irrigation.

Importance of Water Reclamation

Taiwan owns abundant precipitation of 2500mm annually. However, due mainly to the steep topography and inefficient management of water resources, water shortages are common in many parts of the island. In addition, the inequitable distribution of available fresh water supplies at points far distant from where they are needed, inevitably give rise to complex social, economic and legal problems.

Conservation and recycling of water, along with improved management and technology, will contribute to more efficient use. Programs and facilities that will lead to wide spread use of both potable and nonpotable waters will conserve water and reduce its cost. Water reuse projects are implemented for many reasons, including:

Opportunity - Reuse is more opportunistic in nature.
Need - With increasing water demands in areas with limited supplies, reclained water may be the only cost-effective way of supplementing water.
Conservation - Using reclaimed water can significantly reduce the demand.
Reliability of supply - Reclaimed water users may be assured of receiving water
Well-Established Technology - Water reclamation for nonpotable purposes, only requires conventional water treatment technology which is well established.
Economics - Use of reclaimed water may be the most economical option for providing e.g. irrigation.
Pollution Abatement - Using reclaimed water that would otherwise be discharged into environmentally-sensitive water body eliminates a source of contamination.
Public Policy - The public supports reuse is becoming more active in promoting
Successful Experiences - There are literally hundreds of successful experiences.

 

However, the public ¡¦s acceptance and support of reuse projects is based, in part, on its confidence in the safety of reclaimed water.

Water Quality Considerations

The presence of toxic chemicals and pathogenic microorganisms in untreatd wastewater creates the potential for adverse health effects where there is contact, inhalation, or ingestion of chemical or microbiological consitituents of health concern. Thus the acceptability of reclaimed water is dependent on the physical, chemical, and microbiological quality of the water. The chemical and biological constituents of reclaimed water can vary considerably, and determine the success of using such water. Constituents of primary concern appear in Table 1.

Table 1. Constituents of Concern in Wastewater Treatment

Constituent

Reason for Concern

Suspended solids
development of sludge deposits and anaerobic conditions when discharged in the aquatic environment
cause plugging in systems
Biodegradable organics
biological decomposition lead to the depletion of dissolved oxygen in receiving water and development of septic conditions
Pathogens
communicable diseases can be transmitted: bacteria, virus, parasites
Nutrients
P, N lead to the growth of undesirable aquatic life in receiving water
lead to pollution of groundwater
Stable organics
toxic in the environment
H+ activity
affects metal solubility and alkalinity of soils
Heavy metals
toxic in the environment
Residual chlorine
damage to some sensitive crops
toxic effects of chlorinated organics to receiving water
Dissolved solids
ions e.g. Cl, Na, B are toxic to some crops

Factors affecting the quality of water include source water quality, wastewater treatment processes and treatment effectiveness, treatment reliability, and distribution system design and operation. Adequate circulation and aeration are also necessary for algae and odor control. Table 2 shows four ways by which the water can be aerated.

Table 2. Advantages and Disadvantages of Water Aeration Methods.

Aeration Method

Advantage

Disadvantage

Fountain
fairly effective
too much loss in evaporation
Air Injection
highly effective
use 1/5 the energy of fountain
cost up to ten times as much to maintain
Water Falls and Streams
aesthetically pleasing
low maintenance cost
may be high in construction cost
Constructed Wetland
effective at removing toxins and oxygenating the water
water needs to circulate around the plant